Memoirs of Museum Victoria 62(1): 1-66 (2005)

ISSN 1447-2546 (Print) 1447-2554 (On-line)

http://www.museum.vic.gov.au/memoirs/index.asp

Homalonotid trilobites from the Silurian and Lower Devonian of south-eastern

Australia and New Zealand (Arthropoda: Trilobita: Homalonotidae)

Andrew C. Sandford

Department of Earth Sciences, University of Melbourne, Victoria 3010, Australia (andrewsandford@hotmail.com)

Abstract Sandford, A.C. 2005. Homalonotid trilobites from the Silurian and Lower Devonian of south-eastern Australia and New

Zealand (Arthropoda: Trilobita: Homalonotidae). Memoirs of Museum Victoria 62(1): 1-66.

Trilobites belonging to the Homalonotidae are well represented in the Silurian and Early Devonian of south-eastern

Australia and New Zealand, and are a significant component of the family world- wide. Their description provides an

opportunity to review relationships between species and higher order taxa. A new genus Wenndorfia and two new sub-

genera Trimerus ( Ramiotis ) and T. ( Edgillia ) are described, and revised diagnoses are given for Trimerus, Homalonotus,

Dipleura , Digonus and Parahomalonotus. Species described or redescribed from central Victoria include Homalonotus

williamsi sp. nov., H. talenti sp. nov., Dipleura garratti sp. nov., Digonus wenndorfi sp. nov., Trimerus ( Trimerus ) vomer

(Chapman, 1912), T. (T.) harrisoni (McCoy, 1876), T. {Edgillia) kinglakensis (Gill, 1949), T. (E.) jelli sp. nov.,

T. { Ramiotis ) rickardsi sp. nov., T. (R.) tomczykowa sp. nov., T. (R.) otisi sp. nov., T. (R.) thomasi sp. nov. and Wenndorfia

lilydalensis (Gill, 1949). Tasmanian species described include T. (R.) iani sp. nov., Brongniartellal sp. and D. zeehan-

ensis (Gill, 1949). Wenndorfia expansa (Hector, 1876) (= H. {Burmeisteria) huttoni Allan, 1935, = D. margaritifer

Wenndorf, 1990) from New Zealand is redescribed.

Complex relationships between trilobite faunal composition and taphonomy demonstrate that homalonotid

assemblages are inadequately described by the biofacies concept. A recurrent relationship can be recognised between

homalonotid-dominated low diversity assemblages and high diversity assemblages in relatively shallower-water facies

in which homalonotids are minor faunal elements. These paired assemblages occur variously along a bathymetric

gradient that reflects specific environmental tolerances, and precludes the definition of discrete assemblage-facies

associations.

Keywords Trilobita, Homalonotidae, Silurian, Devonian, Australia, New Zealand, systematics, biofacies

Table of Contents

Introduction 1

Geological Setting 2

Taphonomy and biofacies 6

Systematic palaeontology 12

Homalonotus 14

Homalonotus talenti sp. nov 16

Homalonotus williamsi sp. nov 19

Brongniartella sp 21

Digonus 21

Digonus wenndorfi sp. nov 23

Digonus zeehanensis (Gill, 1949) 28

Dipleura 28

Dipleura garratti sp. nov 30

Trimerus 33

Trimerus (Trimerus) harrisoni (McCoy, 1876) 34

Trimerus ( Trimerus ) vomer (Chapman, 1912) 35

Trimerus (Edgillia) subgen. nov 38

Trimerus (Edgillia) kinglakensis (Gill, 1949) 39

Trimerus (Edgillia) jelli sp. nov 41

Trimerus (Ramiotis) subgen. nov 43

Trimerus (Ramiotis) rickardsi sp. nov 44

Trimerus (Ramiotis) iani sp. nov 47

Trimerus (Ramiotis) otisi sp. nov 49

Trimerus (Ramiotis) thomasi sp. nov 53

Trimerus (Ramiotis) tomczykowae sp. nov 54

Wenndorfia gen. nov 55

Wenndorfia expansa (Hector, 1876) 56

Wenndorfia lilydalensis (Gill, 1949) 60

Acknowledgements 62

References 63

Introduction

Homalonotid trilobites were first recorded from south-eastern

Australia and New Zealand as early as the 1860s, and eight

species have been described subsequently including

Homalonotus expansus Hector, 1876, H. harrisoni McCoy,

1876, H. (Burmeisteria) huttoni Allan, 1935, Trimerus lily-

dalensis Gill, 1949, H. vomer Chapman, 1912, T. kinglakensis

Gill, 1949, T. zeehanensis Gill, 1949 and Digonus margaritifer

Andrew C. Sandford

Wenndorf, 1990. The relationships of these taxa have been

poorly understood, as most of them were inadequately

described from limited populations and/or poorly preserved or

incomplete individuals. Museum Victoria houses a large col-

lection of homalonotid specimens from Australasia which not

only permits the redescription of these species, but also the

description of many new species.

Both in taxonomic diversity and abundance the homalonotid

fauna of south-eastern Australia is of world- wide significance.

It is undoubtedly the best preserved representation of the

family for the Llandovery to Lochkovian interval, representing

about one-third of species so far described (Table 1). Three

Llandovery species bring to eight the total number of homa-

lonotids recorded from the interval, with two of them being

among the three best known taxa. Seven Victorian Ludlow

species bring to 15 the total number of homalonotids recorded

from that interval. Similarly, four Lochkovian species make up

one-quarter of the total number of homalonotids recorded from

that interval. The species assigned below to Homalonotus are

two of the total of five assigned to that genus globally, whilst

the nine species assigned below to Trimerus represent almost

half of the species assigned to that genus. A species assigned to

Dipleura is the earliest known representative of the genus,

and two species assigned to Digonus are among the earliest

representatives of that genus.

Historically, the systematics of the Homalonotidae has been

heavily weighted towards the classification of European and

North American species that represent about two-thirds the

total number of species so far described. This trend persists in

the two most recent taxonomic revisions accompanying the

description of north European faunas (Tomczykowa, 1975;

Wenndorf, 1990). In contrast and with the exception of

Burmeisteria, species from Asia, North Africa and the southern

hemisphere have been accommodated in taxa established for

the European and North American faunas. However, problems

arise with the uncritical application of generic concepts estab-

lished for European and North American faunas to the classifi-

cation of southern hemisphere homalonotids, and are manifest

in the nomenclatural changes suffered by some of the few well

documented species. Homalonotus clarkei Kozlowski, 1923

from the Devonian of Brazil has been variably assigned to

Digonus (Wolfart et al., 1968), Trimerus! (Tomczykowa,

1975), Burmeisteria (Cooper, 1982), and Dipleura (Wenndorf,

1990). Similarly, B. ( Digonus ) accraensis Saul, 1967 from the

Devonian of Ghana has been variably assigned to Trimerus

(Tomczykowa, 1975), Burmeisteria (Cooper, 1982) and

Dipleural (Wenndorf, 1990). The comprehensive redescription

of the Australian homalonotid fauna in this work documents a

morphological diversity that demands a more critical usage of

established generic concepts. Revised diagnoses are given in

this work for Homalonotus, Digonus, Parahomalonotus,

Dipleura and Trimerus to accommodate the morphological

diversity of the Australasian fauna.

The Australasian fauna provides new perspectives on the

relationships between species. Trimerus is well represented in

the Australian fauna with nine species assigned to the genus.

The relationships between these and other species of the genus

are formalised in the description of the new subgenera Ramiotis

and Edgillia. T. lilydalensis from Victoria shows closest

relationships to European species previously assigned to

Parahomalonotus. The new genus Wenndorfia is erected

to accommodate T. lilydalensis and these closely related taxa,

and the concept of Parahomalonotus is revised and restricted to

those species close to the type. Reassignment of species

to these groups (Table 1) reflects these revised concepts.

The Silurian and to a lesser extent the Early Devonian are

generally considered periods of cosmopolitanism, and this is

reflected in the widespread distribution of species groups and

higher taxa. Although restricted to the late Wenlock-early

Ludlow, Trimerus ( Trimerus ) is represented in North America,

South America, Europe and Australia, with T. (T.) vomer from

Victoria and T. (T.) johannis Salter, 1865 from England

defining a distinct trans-global species group. Wenndorfia lily-

dalensis from the early Pragian of Victoria is closest to poorly

known species from the late Lochkovian of Europe. The mor-

phological diversity present in the Australian fauna is more a

reflection of the age of the fauna rather than its palaeogeo-

graphic setting. Most of the Australian species are from the

Llandovery, Ludlow and Lochkovian intervals in which many

of the species documented from elsewhere are poorly under-

stood and have had little influence on systematics. Trimerus

( Edgillia ) is erected for a distinct group of globally distributed

Pndolf-early Lochkovian species typified by T. (E.) king-

lakensis from central Victoria but otherwise very poorly repre-

sented in the fossil record. Similarly, T. ( Ramiotis ) is erected for

a widespread group of Llandovery-Ludlow species poorly

represented in the fossil record outside Australia. Siluro-

Devonian homalonotid groups not represented in Australia and

New Zealand include Parahomalonotus, Burmeisteria,

Burmeisterella, Scabrella and Arduenella .

Geological Setting

In central Victoria, trilobite-bearing Silurian to Lower

Devonian marine sedimentary rocks of the Murrundindi

Supergroup crop out in a structurally bound area known as the

Melbourne Zone (VandenBerg et al., 2000). Lithologies are

predominantly interbedded mudstones, siltstones and fine to

medium-grained sandstones, although coarse sandstones and

conglomerates occur at various horizons. Carbonates, known

only from the Lower Devonian in the central and eastern areas

of the Melbourne Zone, are poorly represented and occur as

isolated, discrete limestone bodies.

Homalonotids are restricted in distribution to non-carbonate

sequences between Melbourne, Heathcote and Lilydale in the

western and central areas of the Melbourne Zone (Fig. 1). The

lithostratigraphy of these homalonotid-bearing sequences has

been variously described. The definition, correlation and age of

the various trilobite-bearing lithostratigraphic units described

from these sequences has been reviewed by Rickards and

Sandford (1998) and Sandford (2000, 2002, 2003, 2004).

Stratigraphic nomenclature for the Llandovery to early Ludlow

sequence used in this work (Fig. 2) follows Rickards and

Sandford (1998: fig. 2) and Sandford (2000: fig. 2), and that for

the overlying Ludlow to Pragian sequences follows Sandford

(2002, fig. 2). Homalonotids first appear in the latest

Table 1. Distribution of Silurian and Devonian homalonotid trilobites. Australian species are underlined.

Homalonotid trilobites from the Silurian and Lower Devonian

Andrew C. Sandford

Figure 1. Distribution of fossil marine faunas with homalonotids in south eastern Australia and New Zealand. Localities for the Heathcote,

Springfield- Kinglake West and Lily dale areas are detailed in Figures 8, 11 and 23.

LATE LLANDOVERY WENLOCK LUDLOW PRfDOLI

Homalonotid trilobites from the Silurian and Lower Devonian

EMStAN

PRAGIAN

LOCHKOVIAN

LUDFORDIAN

GORSTIAN

HOMERIAN

SHEINWOODIAN

TELYCHIAN

graptolite,conodont

and brachiopod biozones

recognised in Victoria

ucATum-rc SPRINGFIELD- MELBOURNE-

HtAIHLUIt kinglakewest ULYDALE

pirenae

sulcatus

nilssoni

iudensis

nassa/parvus

testis/

lundgteni

griestonieftsis

Cfispus

turriculatus

Boucotia

loyolensis-

Boucotia

australis

Boucotia

jartaea

Hotopormello

pientlensis

Aegiria

thomasi

TOP NOT EXPOSED

PUCKAPUNVAL

FORMATION

III

MCIVOR

FORMATION

MELBOURNE

FORMATION

VAN YEAN

FORMATION

WAPENTAKE

FORMATION

COSTERFIELD SLT

BASE NOT EXPOSED-

TOP NOT EXPOSED

NORTON

GULLY

SANDSTONE

WILSON

CREEK

SHALE

PUCKAPUNVAL

FORMATION

Cullin' Qu.vry 55 M™

HUMEVALE

SILTSTONE

MELBOURNE

FORMATION

YANYEAN

FORMATION

BYLANDS

SILTSTONE

BASE NOT EXPOSED

AAAAAAAA

LILYDALE

LIMESTONE

Verirtgbeig 5 S Mjfm

HUMEVALE

SILTSTONE

CHRISTMAS

HILLS

FORMATION

MELBOURNE

FORMATION

YANYEAN

FORMATION

Mullum Mullum

Sandstone Member

ANDERSON

CREEK

FORMATION

WarrandyiiCcjl Mem

BASE NOT EXPOSED -J

REEF TON

GROUP

BATON

RIVER

GROUP

W, lilydolertsis

| T(E.)jeili

|d. wenndorfi

T. (E.) kingiakensis

BELL SHALE

FLORENCE

QUARTZITE

ZEEHAN

ci r.mjodsi

y I | T(R.) thomasi

jHiYi/tonosc

D. garratti

| Z(T.) harrisoni

I 7 ™.!

I T?spp.

| T.(R-) tomczykowae

C H I NTI N F M N | T.fRJ rickordsi

TZRJfanl

B.sp.

TIGER RANGE

RICHEA SLT

SPRINGFIELD

SANDSTONE

CENTRAL VICTORIA

DARRAWEIT GUI M PROVINCE

CELL

QUARTZITE

TASMANIA

NEW ZEALAND

Figure 2. Stratigraphic distribution of homalonotids in the Heathcote, Springfield-Kinglake West and Lilydale sequences in central Victoria, and

in Tasmania and New Zealand. Stratigraphic scheme for the Llandovery-Ludlow of central Victoria follows Rickards and Sandford (1998), and

for the Ludlow-Lochkovian follows Sandford (2002).

D.zeehanensis W.expansa

Andrew C. Sandford

Llandovery Chintin Formation at Springfield and occur at

various horizons in the overlying sequences, ranging high in

the Mt Ida Formation at Heathcote in strata considered to be

late Lochkovian in age, and ranging up to the top of the

Humevale Formation at Lily dale in strata considered to be early

Pragian in age. Homalonotids do not occur in the various

Lochkovian-Pragian trilobite faunas from the western areas of

the Melbourne Zone, east of Lilydale. Silurian-Early Devonian

sequences occur widely in Tasmania, but homalonotids are

known only from the south-western areas, in the Llandovery

Richea Siltstone northwest of Maydena and in the Lochkovian

Bell Shale at Zeehan. On the south island of New Zealand,

homalonotid trilobites are known from the Lochkovian-

?Pragian Baton Formation, Baton River and from the ?Pragian-

Emsian Lankey Limestone at Reefton.

Silurian and Devonian trilobite faunas occur widely across

the eastern states of Australia, and the restricted distribution of

homalonotids to the south-western areas of the Melbourne

Zone and to south-western Tasmania is noteworthy. Acastid

trilobites are similarly distributed, whereas the distribution of

harpetid trilobites complements that of the homalonotids and

acastids, ranging from eastern Victoria to northern Queensland.

The limited distribution of homalonotids in eastern Australia

parallels their distribution in Europe across the Rheinischen-

Bohemischen facies boundary. The barrier to dispersal in east-

ern Australia is not apparent for other trilobites, particularly the

phacopids and the calymenids. Echidnops, the Ananaspis

typhlagogus (Opik, 1953) species group and individual species

such as Sthenarocalymene sp. A of Chatterton, Johnson and

Campbell, 1979 are represented both in central Victoria and

New South Wales. It is currently held that the sequences of the

Melbourne Zone were deposited on a low gradient shelf on the

eastern margin of the Australian continental plate. In contrast,

the sequences in eastern Victoria, New South Wales and

Queensland were deposited on off-shore island-arc platforms

many hundreds of kilometres from the mainland (Foster et al.,

1999). It seems that although many trilobite groups were able

to establish themselves in these settings, homalonotids (and

acastids) were unsuccessful in dispersing from the continental

margin. Isolation of the homalonotids can be attributed to pref-

erences for continental margin environments.

Taphonomy and biofacies

The homalonotid-bearing trilobite faunas from the Silurian and

Lower Devonian of central Victoria are quite variable in taxo-

nomic composition and relative abundance of species, taphon-

omy, associated lithofacies and associated non-trilobite faunal

elements. Several faunas can be assigned to homalonotid-

dominated biofacies including the Homalonotid Association

(Mikulic, 1999), the Trimerus delphinocephalus-Dalmanites

limulurus Association (Mikulic, 1999) and the Digonus

Biofacies (Fortey and Owens, 1997). Other faunas resemble the

Acaste-Trimerus Association (Thomas, 1979).

Mikulic (1999) emphasised trilobite elements of Boucot’s

(1975) shallow water ‘Homalonotid-P/ectorcotns BA-1

Community’ in defining the Homalonotid Association. Mikulic

nominated the low diversity/monospecific Ludlow assemblages

dominated by Homalonotus dawsoni Hall, 1860 of the

Stonehouse Formation, Arasaig, Canada as typical. The bio-

facies is associated with coarse- to fine-grained siliciclastics of

nearshore environments and a taphonomy dominated by dis-

articulated exoskeletal elements. Mikulic assigned faunas

ranging worldwide from the Caradoc through to the Givetian to

the Homalonotid Association. Taxa commonly associated with

this assemblage include Acaste, Acastella, Encrinurus,

Scotiella, Dalmanites and calymenids. The Homalonotid

Association can be recognised in the Upper Silurian-Lower

Devonian sequences at Heathcote in central Victoria, repre-

sented by populations of Homalonotus talenti sp. nov.,

Trimerus ( Ramiotis ) thomasi sp. nov. and Digonus wenndorfi

sp. nov. at successive horizons. Most typical is the mono-

specific assemblage at the type locality of H. talenti (PL6650,

Heathcote). The population is preserved in thick-bedded coarse

sandstones of the Mclvor Formation and is represented pre-

dominantly (94%) by isolated sclerites. At its type locality

(PL2203, Heathcote), the population of D. wenndorfi is repre-

sented entirely by isolated sclerites. The species occurs in

medium to coarse sandstones of the Mt Ida Formation in asso-

ciation with rare Acastella sp. and an abundance of very large

bivalves and brachiopods (Fig. 3). The latter indicate alignment

of the fauna to the ‘big-shell community’ of Boucot and

Johnson (1967), later formally designated benthic assemblage

BA-1 (Boucot, 1975) and interpreted to be a very shallow-

water community. The D. wenndorfi fauna at PL2203 can also

be assigned to the Digonus Biofacies of Fortey and Owens

(1997). The Digonus Biofacies was recognised as the shallow-

est in a succession of depth-related trilobite associations of

Early Devonian shelf environments, with deeper associations

named after their characteristic key taxa Scutellum,

Lepidoproetus, Odontochile and Otarion. Although Fortey and

Owens did not provide any description of these associations,

their scheme follows Chlupac’s (1983, 1987) depth-related

succession of lithofacies and trilobite associations described

from the Czech sequences as Major Assemblage Groups I-V.

The association of Digonus, Acastella and an abundance of

bivalves at PL2203 also resembles Thomas’ (1979) Trimerus-

Acaste Association, described from shallow water facies of the

British Wenlock. The Trimerus -Acaste Association can be

regarded as the Silurian equivalent of the Devonian Digonus

Biofacies, both considered here as synonyms of the

Homalonotid Association.

Low diversity trilobite faunas with species of Trimerus and

Dalmanites (or Odontochile) as the two dominant taxa occur at

successive horizons in deeper-water sequences south of

Heathcote. An earliest Ludlow fauna from PL386, Wandong is

dominated by an association of D. wandongensis Gill, 1948 and

T. (T.) vomer. The fauna is preserved in siltstones as isolated

sclerites and partly disarticulated exoskeletons, some of which

represent moult assemblages and indicate a depositional envi-

ronment below storm wave base (Sandford, in press). A late

Ludlow fauna from PL 1898, Eden Park is similarly preserved,

dominated by T. ( Ramiotis ) otisi sp. nov. (relative abundance

96%) with rare Odontochile formosa Gill, 1948 (relative abun-

dance 4%). A late Lochkovian fauna from the upper massive

siltstone beds at Middendorps Quarry (PL252, Kinglake West)

Homalonotid trilobites from the Silurian and Lower Devonian

Figure 3. Sandstone slab from PL2204 (Thomas’ F4, Parish of Dargile), Heathcote with bedding plane showing numerous isolated pygidia and

cranidia of Digonus wenndorfi in various orientations and with large bivalves and brachiopods indicative of Boucot and Johnson’s (1967) ‘big

shell’ community.

is dominated by T. ( Edgillia ) kinglakensis (relative abundance

99%) with rare O. formosa. These assemblages can be assigned

to the T. delphinocephalus-D. limulurus Association, typified

by a trilobite fauna dominated by these taxa from the Wenlock

Rochester Shale, USA. Mikulic (1999) interpreted the commu-

nity as a deeper-water facies association, preserved as disartic-

ulated exoskeletons in fine-grained, deep water/low energy sili-

ciclastics and aligned with BA 4 and BA 5 communities, Brett’s

(1983) Amphistrophia-Dalmanites Community in particular.

Mikulic (1999) tentatively assigned assemblages occurring in

shallower facies (BA3) to the T. delphinocephalus-D. limulurus

Association. Equivalent shallower assemblages in central

Victoria include the O. formosa- dominated fauna from the

lower coquinal siltstones and sandstones at Middendorps

Quarry, in which T. (E.) kinglakensis is rarer.

At a number of localities in the uppermost Humevale

Siltstone at Lilydale Wenndorfia lilydalensis occurs with

Acastella frontosa Shergold, 1968, often as dominant elements

of the fauna. These faunas resemble Thomas’ (1979) Trimerus-

Acaste Association, although the facies at Lilydale suggest a

deeper-water setting. Another acastid, Acaste lokii Edgecombe,

1993, occurs lower in the Humevale Siltstone in the Lily-

dale area, its stratigraphic range overlapping with that of

W. lilydalensis, but the two species never occur together.

Despite the recognition of homalonotid biofacies at several

localities, the homalonotid faunas of south-eastern Australia are

otherwise inadequately described by the biofacies concept.

Patterns can be recognised demonstrating more complex

relationships between homalonotid relative abundance, faunal

diversity, taphonomy and lithofacies. A skewed inverse

relationship between relative abundance and faunal diversity

can be demonstrated, with lower diversity trilobite associations

having homalonotids proportionally over-represented, and

higher diversity associations with homalonotids under-

represented. In the higher diversity faunas, dalmanitids or

proetids are frequently the dominant taxon, although acastids,

phacopids and rarely odontopleurids may also dominate. The

relationships between taxonomic diversity and homalonotid

relative abundance is best expressed graphically (Fig. 4).

Several species from central Victoria including Digonus

wenndorfi, Trimerus ( Edgillia ) kinglakensis, T. ( Ramiotis )

otisi and Wenndorfia lilydalensis are known from both low

Andrew C. Sandford

AB2, AB1, AA34 r AA14, G62,G58

100

Q PL 252 {upper slltstone)

ijD 4 .PL1 898

1 LOWER DIVERSITY

HOMALONOTIDS

\ FAUNAS

OVER-REPRESENTED

\ H 45

\ Q

Oh46 0 S5R

C' C3

%\ ° 7

Qg 59

O i

1\ O a, °

q i

7 -\ O gm

<v.

0 Q2

O- ^ O G 1 Qa B 1 0

P L 3 0 0 Q 0-1 __

HIGHER DIVERSITY FAUNAS

BWSO QPL1990

"O'

Qg 69

G 1 3 O

QR25

Q PL2S2

P G87 n

n G5 ^

R 2 1 S R25E

HOMALONOTIDS UNDER-REPRESENTED

(coquinas)

2 3

4 5 6 7

8 9

1 0

TAXONOMIC DIVERSITY

Figure 4. Relationship between trilobite faunal diversity and homalonotid relative abundance. Only homalonotid-bearing faunas represented by

more than 10 specimens are plotted. The curve connects plot-points of hypothetical faunas where species are represented in equal proportional

relative abundance. Homalonotid faunas cluster in two groups, lower diversity faunas with homalonotids over-represented (above the line) and

high diversity faunas with homalonotids generally under-represented (below the line).

diversity, homalonotid-dominated assemblages and high

diversity assemblages in which homalonotids are under-repre-

sented. From these occurrences, a pattern emerges revealing a

relationship between trilobite assemblage composition, taphon-

omy and lithofacies (Table 2). This relationship is best illus-

trated in the distribution of T. (E.) kinglakensis in the upper

massive siltstones and the lower bedded coquinal siltstones and

sandstones at Middendorps Quarry, where a marked contrast in

facies accompanies differences in faunal composition. In the

upper beds T. ( E .) kinglakensis is extremely dominant (relative

abundance 99%) in a low-diversity assemblage accompanied

by rare Echidnops hollowayi Sandford, 2002 and Odontochile

formosa. Individuals are preserved predominantly as partly

articulated and frequently incomplete exoskeletons or other-

wise as isolated pygidia. Despite the exceptionally high pro-

portion of partly articulated exoskeletons, complete fully artic-

ulated exoskeletons are absent. Many of the partly articulated

exoskeletons can be interpreted as moult assemblages, pre-

served in typical phacopid fashion with the cephalon displaced,

often inverted and/or lying underneath the thoracopygon (Figs

5 A, 5D). Partly-articulated thoraces can be interpreted as ele-

ments of moult assemblages scattered by the movements of the

animal during the exuvial process. Indeed, it is probable that

the whole population of T. (E.) kinglakensis in the massive silt-

stones (including the isolated cephala and pygidia) are derived

from exuviae rather than dead individuals.

Well bedded, siltstones and graded sandstones with poorly

sorted, bioclastic basal coquinal lags underlie the siltstones at

Middendorps Quarry and yield a much more abundant and

diverse benthic fauna. By world standards ten taxa is low diver-

sity for an Early Devonian trilobite assemblage, but for central

Victoria this is one of the most diverse. The assemblage is dom-

inated by Lepidoproetus sp. and Odontochile formosa with a

combined relative abundance of 64%. Trimerus (Edgillia)

Homalonotid trilobites from the Silurian and Lower Devonian

Table 2. Relationships between lithology, relative abundance and taphonomy for Trimerus (Edgillia) kinglakensis, Trimerus ( Ramiotis ) otisi and

Wenndorfia lilydalensis. Populations of the latter species in the Eden Park and Humevale siltstones are taken as a whole.

Trimerus (Edgillia)

kinglakensis

Humevale Formation

PL252 (type locality)

Trimerus (Ramiotis) otisi

Eden Park Formation

Wenndorfia lilydalensis

Humevale Formation

LITHOLOGY

siltstone

coquina

siltstone

coquina

siltstone

(Clonbinane

Sandstone

Member:

PL300, PL6642)

coquina

(PL 1804)

TOTAL specimens

286

132

RELATIVE ABUNDANCE

99%

15%

96%

24%

26%

TAPHONOMY

complete dorsal exoskeleton

40%

36%

100%

cephalothorax

<1%

1.5%

13%

cephalon with displaced thoracopygon

12%

cephalon with displaced thorax

10%

1.5%

cephalon with displaced thorax and

displaced pygidium

cephalon

11%

17%

isolated cranidium

<1%

17%

12%

isolated librigena

isolated hypostome

articulated/partly articulated thorax

loosely disarticulated thorax

<1%

isolated thoracic segment

13%

21%

partly disarticulated thorax, displaced pygidium

complete/partly complete thoracopygon

36%

13%

isolated pygidium

15%

60%

48%

25%

41%

articulated/partly articulated specimens

84%

40%

70%

75%

21%

100%

TAPHOFACIES

TIV

Till

TIV

Till

TIV

Till

kinglakensis is a minor faunal element (relative abundance

<3%). In further contrast to its representation in the overlying

siltstones, the population of T. (E.) kinglakensis in the coquinas

has a high proportion (13%) of complete, fully articulated

exoskeletons. Populations of other species in these beds also

have a high proportion of complete exoskeletons, including

Lepidoproetus sp. (42%), Maurotarion sp. (33%), Echidnops

hollowayi (21%), Leonaspis sp. (11%) and Dicranurus king-

lakensis Gill, 1947 (6%).

Similar relationships between faunal composition and

taphonomy can be demonstrated for Trimerus ( Ramiotis ) otisi

and Wenndorfia lilydalensis. The single known complete

exoskeleton of W. lilydalensis from PL 1804, Coldstream is

exceptional in several respects. It occurs in a bioclastic

coquinal lag within a fine-grained sandstone (Fig. 5C), ident-

ical to the style of preservation of T. ( Trimerus ) harrisoni at

PL 1820, West Brunswick (Fig. 5B) where most specimens

(58%) are complete exoskeletons. The relative abundance of W.

lilydalensis at PL 1804 is very low (2%), exceptionally under-

represented in an assemblage of relatively high diversity

(8 species). By contrast, all other specimens of the species

including isolated tergites and partly disarticulated exo-

skeletons occur in thick-bedded siltstones at various localities

in the Lilydale area. The relative abundance of the species in

the siltstones ranges between 6% and 100%, with assemblages

comprising one to six species in which W. lilydalensis is

moderately under-represented or over-represented (Fig. 4). In

the siltstones of the Eden Park Formation in the Eden Park area

T. (R.) otisi occurs in monospecific assemblages or dominates a

low diversity assemblage also containing rare Odontochile

formosa. In these beds T. (R.) otisi is preserved predominantly

as isolated sclerites or partly articulated exoskeletons, many of

which can be recognised as moult assemblages. The holotype is

a complete exoskeletion with the cephalon displaced and lying

underneath the thoracopygon. The ratio of articulated speci-

mens is 25%, 5% being typical phacopid moult assemblages

and less than 1% being fully articulated individuals. T. (R.) otisi

also occurs in the overlying Clonbinane Sandstone Member, in

medium grained sandstone and coquinal bioclastic lags. At

PL300, Clonbinane it is under-represented (relative abundance

17%) in a higher diversity assemblage also containing

Echidnops hollowayi, O. formosa, Dicranurus sp. and an

Andrew C. Sandford

Figure 5 A, D. Moult assemblages of Trimerus ( Edgillia ) kinglakensis in the upper siltstones at PL252, Middendorps Quarry, Kinglake West,

Humevale Siltstone. A, upper right, displaced and inverted cephalon lying underneath thoracopygon (only anterior margin visible); left, thora-

copygon with displaced and rotated cephalon. D, thoracopygon with displaced and rotated cephalon. B-C. Complete dorsal exoskeletons in sand-

stone bioclastic coquinas. B, Trimerus ( Trimerus ) harrisoni from PL 1820, Brunswick, Melbourne Formation. C, Wenndorfia lilydalensis from

PL 1805, Coldstream. Humevale Siltstone.

odontopleurid. More than one third of all trilobites in these beds

are complete, fully articulated exoskeletons. As in the bedded silt-

stones and coquinal lags at Middendorps Quarry, the assemblage

at PL300 is associated with a rich echinoderm fauna.

The taphonomy of the trilobite exoskeleton is an important

palaeoenvironmental indicator. The multitude of sclerites of

which the exoskeleton was composed responded in a complex

way to the depositional environment in which they were

ultimately preserved. Detailing the proportions of fragmented

tergites, convex-up tergites, articulated tergites, enrolled

individuals and moult assemblages in trilobite populations

from the Middle Devonian Hamilton Group, New York, Speyer

and Brett (1986) defined a sequence of trilobite taphofacies

(taphofacies 1A-B, 2A-B, 3A-B and 4A-C) interpreted to

reflect depth and rates of sedimentation. Sandford (2002)

described a similar depth-related sequence of trilobite taphofa-

cies for the phacopid-dominated assemblages (TpI-TpIV) and

the homalonotid-dominated assemblages (ThI-ThIV) of the

Late Silurian-Early Devonian of south-eastern Australia.

Whilst there is some credit in distinguishing between

taphonomies for thick-shelled forms and thin-shelled forms in

shallower facies, these forms occur in both phacopids and

homalonotids. The separate Tp-Th classification of tapho-

nomies is not justified, and abandoned here in place of a

broader TI-IV classification, which can be more widely applied

to trilobite taphofacies. Although this study is based almost

entirely on museum specimens and the proportion of convex-up

specimens cannot be accurately determined, Speyer and Brett’s

taphofacies can be recognised for the homalonotid faunas of

south-eastern Australia. Assemblages preserved in fine-grained

Homalonotid trilobites from the Silurian and Lower Devonian

articulated dement*

in well wrtcd and

bedded sjndilonrl

in poorly sorted b*ocla*tic

siltstone bt S

coquina*

(moult assemblage*] in

siltstone; few complete

cuoiketiorij

Wenndorfia lityddensh

Trimerus (EdgiHio)jelli

Trimerus (Btgillfa) klngfakensis

Trimenis ( Ramiotis ) otisi

Homalonotus talenti

Homalonotus willion

Dipleura garratti

Trimerus (Trimenis) horrisonl

Trimerus (Trimerus) vomer

Trimenis (Ramioiis) tomczykowae; Trimerus spp.

Trimenis (Ramiotis) rlckardsl

Trimerus (Ramiotis) iani

Figure 6. Facies and environmental distribution of Australian homalonotids.

lithologies with a high relative abundance of moult assem-

blages (or partly disarticulated exoskeletons), a low abundance

or absence of complete, fully articulated exoskeletons, a low

degree of isolated sclerites and low or negligible breakage can

be assigned to Sandford’s taphofacies TIV (-Speyer and Brett’s

taphofacies 4A). The preservation of moult assemblages

indicates deposition at depths below maximum storm wave

base, where current activity was minimal and reworking of

exoskeletal elements was negligible. Assemblages preserved in

poorly sorted bioclastic coquinal lags with a high relative

abundance of complete, outstretched exoskeletons, an absence

of moult assemblages and a moderate degree of breakage can

be assigned to Sandford’s taphofacies Till. This taphofacies is

interpreted to reflect depths around storm wave base and is

analogous to Speyer and Brett’s taphofacies 3A, although dif-

fering from it in the lower representation of moult assemblages

and enrolled specimens relative to outstretched specimens. The

basal lags represent proximal tempestites generated from the

peak of storm activity, during which highest energy currents

rapidly concentrated and buried large bioclasts (both living and

dead), with complete exoskeletons representing smothered

individuals.

Taphofacies associations for Wenndorfia lilydalensis,

Trimerus ( Edgillia ) kinglakensis and Tn'merus ( Ramiotis ) otisi

populations demonstrate that the low diversity, homalonotid-

dominated assemblages inhabited deeper bathymetries than the

higher diversity assemblages in which homalonotids are under-

represented. A similar relationship can be demonstrated for

populations of Digonus wenndorfi from the Heathcote

sequence, but in a shallower water context. At several localities

including the type locality PL2204, Heathcote, D. wenndorfi

occurs in abundance in monospecific or very low diversity

assemblages. The taphonomy is characterised by a high relative

abundance of isolated sclerites (80-95%), minimal breakage

and a high concentration of elements, with the articulated spec-

imens mostly represented by cephala. Thick-bedded, medium

to coarse-grained, well-sorted sandstone lithologies are associ-

ated with this taphofacies. Sandford (2002) designated this

preservation taphofacies Til, equivalent to Speyer and Brett’s

(1986) taphofacies IB, and it is interpreted to reflect deposition

at depths around normal wave base, where moderate energy

current action gently winnowed finer sediments, and disartic-

ulated and concentrated skeletal elements in coarser lithologies.

At PL2327, Heathcote D. wenndorfi occurs in a high diversity

Andrew C. Sandford

fauna of ten species as a proportionally represented species

(relative abundance 11%). The assemblage is dominated by

Echidnops hollowayi and Odontochile formosa. In contrast to

the preservation of the D. wenndorfi- dominated assemblages,

that at PL2327 is characterised by a high proportion of iso-

lated and broken sclerites (broken specimens 20%, isolated

sclerites 98%). This preservation is generally associated with

coarser-grained lithologies, typically thick, coquinal sand-

stone with poorly sorted, randomly oriented bioclasts and can

be assigned to Sandford’s taphofacies TI, equivalent to

Speyer and Brett’s taphofacies 1A. A high proportion of iso-

lated and broken sclerites suggests an environment of deposi-

tion in very shallow environments (<20 m) above normal

wave base, with medium to high energy oscillatory wave-

generated currents reworking, fragmenting and winnowing

skeletal elements.

The paired assemblages occur variously in very shallow,

moderate or deep water facies that reflect specific environ-

mental tolerances and preclude the definition of discrete

assemblage-facies associations. The facies distribution of

south-eastern Australian homalonotids is shown in Fig. 6.

The relationship between homalonotid-dominated low

diversity assemblages in deeper water facies and high diversity

assemblages in which homalonotids are minor faunal elements

in shallower-water facies are not generally consistent with

Mikulic’s (1999) and Thomas’ (1979) observations that homa-

lonotid species dominating shallow- water assemblages occur

as rare elements of assemblages in deeper facies. For Digonus

wenndorfi, Trimerus ( Edgillia ) kinglakensis and Trimerus

( Ramiotis ) otisi the opposite is true, being under-represented or

rare in shallower environments and dominant in deeper

environments. Rather than declining in abundance in even

deeper environments, species are replaced by a different

species. T. (E.) kinglakensis inhabits the deeper environments

of the Lochkovian, whereas T (E.) jelli and D. wenndorfi

inhabit the contemporary shallow and very shallow environ-

ments. Similarly, T. ( R .) otisi inhabits the deeper environments

of the late Ludlow, whereas T (R.) thomasi inhabits the con-

temporary shallow environments. An exception is the distribu-

tion of W. lilydalensis, which is consistent with both the pattern

described above and with the observations of Mikulic and

Thomas. As noted above, W. wenndorfi is rare in the shallower

coquinal sandstones at PL 1804 and dominates many of the

trilobite faunas in the deeper siltstones of the upper Humevale

Siltstone at Lilydale. In the siltstones, the association of

Acastella frontosa and W. lilydalensis alternates with another

association of calymenids and/or phacopids, variously com-

prising Sthenarocalymene angustior (Chapman, 1915),

Nephranomma debrae, N. lynnae and Lochkovella longisulcata

(Shergold, 1968). The latter association is dominant in the

deepest water facies, with taphonomies including enrolled indi-

viduals and often occurring with Harpidella sp. in abundance.

At the few localities where the association of A. frontosa and

W. lilydalensis occurs in these deepest water facies it is only in

low abundance with the calymenid-phacopid associations

dominant. These mixed faunas resemble the deeper water

equivalents of Thomas’ Acaste-Trimerus association, where

Calymene becomes common.

Systematic palaeontology

The description of the homalonotid trilobites from central Victoria is

based on collections in Museum Victoria (NMV), registered with pre-

fix P. This collection includes specimens previously held by the

Geological Survey of Victoria (previously registered with prefix GSV)

and the University of Melbourne, Geology Department. Other speci-

mens cited include those at the Geological Survey of New Zealand

(NZGS) (registered with prefix AR) and at the Canterbury Museum,

Christchurch, New Zealand (registered with prefix ZFc). Trilobite

specimens are preserved in mudstones as internal and external moulds.

Internal moulds were coated with colloidial graphite, latex peels have

been made from external moulds, and all have been whitened with

a mm onium chloride for photography. Trilobite localities are registered

with prefix PL in Museum Victoria. These include previously pub-

lished fossil localites of Jutson (1908: pi. 3), Thomas (1940a, 1940b,

1941, 1956, 1960), Gill and Banks (1950), Gill (1940: fig.l; 1945: fig.

2), Talent (1964: fig. 1), Williams (1964: fig. 2), Moore (1965: fig.l),

VandenBerg (1970), Garratt (1972, 1977), Jell and Holloway (1983:

fig. 1), Holloway and Sandford (1993: fig. 1), Wall et al. (1995: fig. 1)

Rickards and Sandford (1998: fig. 6) and Sandford (2000: fig. 7; 2002:

fig. 1; 2003: text-fig. 1; 2004: fig. 1; 2005: figs 2-4). Trilobite local-

ities in the Heathcote, Kilmore-Kinglake West, Springfield and

Lilydale areas are shown in Figs 8, 11 and 23.

Terminology used in this study for the description of the trilobite

exoskeleton (Fig. 7) generally follows current standard nomenclature

reviewed by Whittington (1997) and Whittington and Kelly (1997).

Terminology specific to the description of homalonotid trilobites has

been introduced by Tomczykowa (1975), Wenndorf (1990) and

Whittington (1993). Wenndorf established several new terms including

‘AuBendom’, referred to as the posterolateral pleural spine in this

work, and the ‘Gelenkleiste’ in reference to ridges that overhang and

partly enclose the trench-like furrow traversing each thoracic segment.

Wenndorf also established a set of measurements and derived ratios

specifically for the description of homalonotids. In accord with

Wenndorf, the glabellar width is measured across LI -LI rather than the

across occipital ring (where the axial furrows are very poorly defined)

and the pygidial axial width is measured across the second axial ring

rather than the first ring, for the same reason. To avoid ambiguity this

width is referred to as the preoccipital glabellar width. However in this

work, following the description of other trilobites, the glabellar length

includes the length of the occipital ring and the pygidial axial length

includes the length of the terminal axial piece. Whittington (1993)

introduced the term ‘articulating and pleural furrow’ to describe the

furrow traversing thoracic segments, considered to be homologous to

the independent pleural and articulating furrows of other trilobites.

‘Rib-ring offset’ is a term introduced in this work to describe differ-

ences in segmentation of the pygidial axis and pleural lobe in homa-

lonotids. Rib-ring offset is a modification of R-P ratios often described

for encrinurids, but impractical in describing homalonotid pygidia

where segmentation is often poorly defined or effaced posteriorly. It is

expressed by the n-th pleural rib when the transverse midline of that rib

intersects with the axial furrow opposite a pygidial ring furrow.

Order PHACOPID A Salter, 1864

Suborder CALYMENINA Swinnerton, 1915

Superfamily CALYMENOIDEA Burmeister, 1843

Family Homalonotidae Chapman, 1890

Remarks. Organisation of the Homalonotidae here follows

Thomas (1977) who discussed previous divisions of the family.

Subfamily Homalonotinae Chapman, 1890

Homalonotid trilobites from the Silurian and Lower Devonian

CEPHALON (DORSAL VIEW)

connective suture (dorsal section)

rostral suture

preglabellar field

preglabellar furrow

axial furrow

median indentation

frontal lobe

glabellar lobes (L1-L3)

lateral glabellar furrows (SI -S3)

apodemal pit

muscle scar

CEPHALON (VENTRAL VIEW)

rostral plate (ventral section)

librigenal doublure

posterior branch of facial suture

(ventral section)

THORACIC SEGMENT (OF 13)

PYGIDIUM (DORSAL VIEW)

articulating half ring

articulating furrow

articulating facet

inter-ring furrow

axial ring

axial furrow

rostral plate (dorsal section)

anterior branch of facial suture

preocular fixigenal field

. eye ridge

lateral border furrow

palprebral area

palpebral lobe

visual surface

subocular groove

librigenal field

sutural furrow

posterior branch of facial suture

(dorsal section)

postocular fixigenal area

paraglabellararea (ala)

posterior border furrow

posterior border

anterior wing

anterior lobe of middle body

lateral border furrow

macula

middle furrow

posterior lobe of middle body

posterior border furrow

median notch

posterior border lobe

articulating half ring

articulating and pleural furrow

anterior band of pleura

articulating facet

posterior band of pleura

axial furrow

axial articulating process

axial ring

pleural furrow

pleural rib

lateral border

lateral border furrow

V hypostome

pleural

lobe

posterior axial swelling

terminal axial piece

postaxial ridge/ field

terminal pygidial spine

Figure 7. Morphological terms for the homalonotid exo skeleton.

Andrew C. Sandford

Genera and subgenera included. Homalonotus Konig, 1825, Trimerus

( Trimerus ) Green, 1832, Trimerus ( Ramiotis ) subgen. nov., Trimerus

( Edgillia ) subgen. nov., Digonus Gtirich, 1909, Dipleura Green, 1832,

Brongniartella Reed, 1918, Burmeisteria Salter, 1865, Burmeisterella

Reed, 1918, Scabrella Wenndorf, 1990, Arduenella Wenndorf, 1990,

Parahomalonotus Reed, 1918, Platycoryphe Foerste, 1919,

Wenndorfia gen. nov.

Discussion. Classifications of the Homalonotinae by Reed

(1918), Sdzuy (1959), Tomczykowa (1975), Thomas (1977)

and Wenndorf (1990) have variously emphasised particular

features of the exoskeleton including glabellar lobation, glabel-

lar outline, the course of the cephalic suture, the length of the

preglabellar field, the morphology of the anterior cephalic mar-

gin, the shape of the rostral plate, the expression of a rostral

process, eye position, pygidial outline, the outline of the

pygidial axis, and the expression and degree of pygidial seg-

mentation as characters of generic significance. Differences

between these classifications reflect different emphases on

diagnostic characters. The diversity of morphologies expressed

within genera is greatly enhanced by the Australian fauna and

necessitates a review of current generic concepts. A new genus

Wenndorfia and two new subgenera Trimerus {Ramiotis) and

T. ( Edgillia ) are described, and revised diagnoses are given for

Trimerus, Homalonotus, Dipleura, Digonus and

Parahomalonotus.

Homalonotus Konig, 1825

Homalonotus Konig, 1825:104.

Koenigia Salter, 1865: 119.

Type species. Homalonotus knightii Konig, 1825 from the Ludlow of

England, by monotypy. The type species has been recorded from

Britain, Germany, Poland and Canada, although its the relationship to

the Canadian H. dawsoni is not clearly established. Hall (1860)

described dawsoni solely from pygidia, and his diagnosis clearly allies

the species with knightii and the Swedish H. rhinotropis. McLeam

(1924) suggested that differences in pygidial morphology easily dis-

tinguish dawsoni from knightii, citing the posterior projection of the

pygidial axis, narrower proportions and less convex profile of the lat-

eral margin as distinguishing the type species. On these criteria

McLeam identified specimens from the McAdam and Moydart

Formations at Arasaig, Nova Scotia as knightii, and those from the

slightly younger Stonehouse Formation in the same area as dawsoni.

The cephalic morphology of dawsoni was described by Dawson (1868,

1877) and McLeam. McLearn noted that the two cephala known from

the McAdam and Moydart Formations were very similar to those of

dawsoni from the Stonehouse Formation. Indeed, a relatively unde-

formed cephalon from the Moydart Formation examined by the author

is clearly attributable to dawsoni rather than knightii. The specimen is

comparable to the Stonehouse Formation cephala in the anterior place-

ment of the eyes and more elongate and more-weakly tapering glabel-

lar shape, distinguishing the Canadian species from the type species.

The specimen also shows the acutely pointed lateral cusps of the ante-

rior margin, not previously documented. Whether the differences in

pygidial morphology between the McAdam and Moydart Formation

populations are significant is a question that cannot be resolved with-

out detailed re-examination of the faunas.

Other species included. Homalonotus dawsoni Hall, 1860, H.

rhinotropis Angelin, 1852, H. williamsi sp. nov., H. talenti sp. nov.

Range. Ludlow, possibly early Pndoli . England, Germany, Poland,

Sweden, eastern North America and south-eastern Australia.

Revised diagnosis. Cephalon much wider than long. Glabella

long (length 1.1- 1.3 times width), tapering forward weakly to

moderately (15-30°), sides straight, lobation weak to indistinct.

Paraglabellar area distinct. Preglabellar furrow present, of vari-

able depth (shallow to very deeply impressed). Preglabellar

field very short (<0.08 times cranidial length). Anterior margin

of cephalon tricuspid with a strongly folded (M- shaped) profile

in dorsal view. Central cusp triangular, and strongly convex

downwards in anterior view. Facial suture and rostral suture

meeting at invagination of anterior margin such that connective

suture is absent dorsally. Eyes forwardly placed, opposite

0.55-0.7 glabellar length. Pygidial lateral border furrow

distinct, anteriorly lateral border swollen, lip-like, fused ven-

trally with rolled doublure and continuous with long (exsag.)

articulating facet.

Discussion. Sdzuy’s (1959) diagnosis of Homalonotus reiter-

ates the characters listed by Reed (1918), omitting only the

‘angular course of the anterior branch of the facial suture’.

Additional characters listed by Sdzuy include features of the

glabella (indistinct lobation, trapezoidal shape), the rostral plate

(lacking a process), the folding of the anterior margin, and the

presence of a cephalic border (i.e. that defined by the preg-

labellar furrow). The preglabellar furrow is variable in depth,

being very deeply impressed in H. williamsi and H. talenti,

moderately impressed in H. dawsoni (see McLearn, 1924: pi.

27, fig. 14) and H. rhinotropis (see Angelin, 1878: pi. 20, fig.

1). In the type species, the depth of the preglabellar furrow

varies from shallow (e.g. Tomczykowa, 1975: pi. 1, figs 1, 3) to

moderately impressed (e.g. Salter, 1865: pi. 12, fig. 2) and sug-

gests the presence/absence rather than the depth of the furrow

is of significance.

The assignment of two new Australian species to the genus

indicates a somewhat broader range of morphologies for the

genus than represented by the northern hemisphere species,

particularly in features of the pygidium. Homalonotus knightii,

H. rhinotropis and H. dawsoni share a distinct pygidial mor-

phology characterised by raised, long pleural ribs that are con-

tinuous with the axial rings (separated by a deep, continuous,

pleural and ring furrows), effaced axial furrows, by a fused

postaxial ridge and posterior area of pleural field, and by a

strongly acuminate tip. In contrast, the pygidial axial furrows of

H. williamsi and H. talenti are only moderately impressed (Figs

10.3-10.11). In williamsi the axis is raised, defining distinct

pygidial trilobation, the postaxial ridge is not fused with the

posterior area of the pleural field, whilst in talenti the pleural

and ring furrows are shallow and the posterior tip is rounded.

The revised diagnosis given above accommodates these mor-

phologies by excluding all pygidial characters listed in Sdzuy’s

(1959) and Tomczykowa’s (1975) diagnoses, including the

‘acuminate triangular and acutely tipped pygidial outline’, the

‘weakly defined trilobation’, the ‘posterior fusion of axis and

pleural field’ and the ‘distinct segmentation’. Nevertheless, the

pygidial morphology characterising the contemporary northern-

hemisphere species defines a species group distinct from the

Australian taxa and reflects a degree of provincialism not

otherwise seen in homalonotid distribution.

The distinctive morphology of the pygidial lateral border is

Homalonotid trilobites from the Silurian and Lower Devonian

listed as an additional diagnostic character. The complex anter-

ior cephalic margin of Homalonotus corresponds to a complex

coaptive morphology. Laterally, the swollen, lip-like section of

the pygidial border-doublure defines the overlap of the libri-

gena, the pygidial border-doublure fitting against the cephalic

doublure. The pygidial doublure is narrow posterior to the lip-

like section, and at this point the doublure of the enrolled

pygidium emerged from underneath the anterior cephalic

border at the invagination of the anterior margin. The anterior

margin of the rostral process fitted against the posterior margin

of the pygidial doublure, as indicated by the matching convex-

ity of these structures (in anterior/posterior view) in H. talenti

(Figs 9.5b, 10.7c).

Several of the cephalic features listed as generic characters

by Sdzuy (1959) are excluded from the revised diagnosis,

including the ‘indistinct glabellar lobation’ and the ‘median

point on the rostral suture’. These characters are excluded to

accommodate the Australian species, that lack a median point

on the rostral suture, whilst Homalonotus williamsi exhibits

weak glabellar lobation. Sdzuy noted the difficulty in interpret-

ing the anterior border of Homalonotus. However, the junction

of the facial suture and rostral suture at the invagination of the

anterior margin (and the absence of the connective suture

dorsally) is clearly evident on williamsi, and is comparable to

the morphology of the anterior margin of H. rhinotropis

described by Moberg and Gronwall (1909).

Sdzuy (1957), Tomczykowa (1975) and Thomas (1977)

considered Homalonotus to have been derived from Trimerus

and interpreted H. ( T .) johannis Salter, 1865 as transitional

between the genera. Wenndorf (1990) expressed uncertainty on

this derivation of Homalonotus. Reed (1918) tentatively placed

johannis in Homalonotus, primarily on account of its tricuspid,

folded anterior margin and supposed pygidial similarities, but

noted that long preglabellar field of johannis differed markedly

from that of H. knightii. Although Prantl and Pribyl (1948)

suggested a new genus or subgenus be erected for johannis,

Sdzuy (1957) retained the species in Homalonotus. The length

of the preglabellar field is only one of many differences

between knightii and johannis indicating that these species are

not related. Whilst johannis shares with the northern hemi-

sphere species of Homalonotus ( knightii , H. dawsoni and

H. rhinotropis ) deeply impressed pygidial pleural and ring fur-

rows and an elongate, acutely tipped triangular outline, it lacks

the effaced trilobation and fused postaxial area characterising

those species. More importantly, johannis lacks the swollen

lip-like pygidial border shared also by the Australian species

and considered diagnostic of the genus. The species also differs

markedly from Homalonotus in having a highly derived

cranidial morphology. The raised glabella which is markedly

expanded across LI -LI (tr.) and has deep SI apodemes and a

distinct sagittal ridge, the strong expression of the medial

indentation of the anterior glabellar margin and paraglabellar

areas, and the long and weakly convex (tr.) preglabellar field

indicates assignment of Salter’s species to Trimerus (Trimerus),

in agreement with Tomczykowa’s (1975) and Morris’ (1988)

assignment.

Of the species assigned in this work to Homalonotus,

H. williamsi appears to be the least derived. H. williamsi retains

Figure 8. Geological sketch map of the Heathcote area showing

Wenlock-Lochkovian fossil localities yielding homalonotids. For other

fossil localities see also Thomas (1940a, 1940b, 1941, 1956), Talent

(1964, fig. 1), Sandford (2002, fig. 1A; 2005, fig. 4).

Andrew C. Sandford

distinct glabellar lobation, the axial furrows are moderately

impressed, the pygidial axis is raised posteriorly and the

postaxial area is not fused with the pleural field. In these

respects williamsi shares features of Trimerus possibly reflect-

ing the relationship suggested by Sdzuy, Tomczykowa and

Thomas. The interpretation of williamsi as morphologically

primitive supports the derivation of Homalonotus from

T. ( Ramiotis ) rather than from the more derived T. (Trimerus).

Of species assigned to T. (Ramiotis), williamsi bears closest

resemblance to T. (R.) otisi (Fig. 20), which bears a well-devel-

oped tricuspid cephalic margin comparable to that of T. (T.)

johannis, though more weakly folded. As with several other

Upper Silurian species of T. (Ramiotis), otisi also a exhibits a

well defined pygidial border furrow and swollen lip-like border

comparable to that of Homalonotus, a morphology otherwise

only poorly developed or absent in other groups including

T. (Trimerus) and T. (Edgillia). T. (R.) otisi lacks the strongly

derived glabellar features of johannis, sharing with Homa-

lonotus the elongated, weakly tapering glabella with weak

lobation. In these respects otisi is a more likely candidate than

johannis in representing an intermediate morphology between

Trimerus and Homalonotus, although its interpretation as an

ancestral species is not in accord with its stratigraphic position,

otisi appearing in strata immediately overlying those yielding

williamsi.

Homalonotus talenti sp. nov.

Figures 9, 10.5-10.11

Homalonotinae gen. et sp. indet. 2. — Holloway and Neil, 1982: 146,

fig. 4I-L. — Morzadec, 1986: 186.

Type material. Holotype NMY P304936 (cephalon) from PL6650,

Heathcote, Victoria (Fig. 9.1). Paratypes NMV P304927, NMV

P304937-P304939 (cephala), NMV P304923-P304925, NMV

P304928, P304929 (cranidia), NMV P304941, NMV P304943 (libri-

gena), NMV P304946-P304948 (hypostomes), NMV P304945, NMV

P304949 (thoracic segments), NMV P304917, P304918, NMV

P304920-P304922 (pygidia) from PL6650. Paratypes NMV P304952,

P304953 (pygidia) from PL6651, Heathcote. For localities see Fig. 8.

Previously figured material. NMV P78296 (ex GSV35724, cephalon,

figured Holloway and Neil, 1982: figs 41, 4J), NMV P78297 (ex

GSV35725, pygidium, figured Holloway and Neil, 1982: figs 4K, 4L)

from PL2239, Thomas locality F25, Parish of Heathcote, Heathcote.

For locality see Fig. 8.

Registered material. 127 specimens: 10 cephala, 41 cranidia, 9 librige-

nae, 3 hypostomes, 8 thoracic segments, 56 pygidia. NMV

P3049 1 7-P30495 1 , NMV P304959-305026 from PL6650. NMV

P304952-P304957, NMV P305027-P305029 from PL6651. NMV

P304958, NMV P305041 from PL2265, Thomas locality F46, Parish

of Heathcote, Heathcote. NMV P78296, P78297 from PL2239. NMV

P305030-P305040 from PL2207, Thomas locality F7, Parish of

Dargile, Heathcote. For localities see Fig. 8.

Stratigraphic distribution. Upper beds of the Mclvor Sandstone and

lowermost beds of the Cornelia Member of the Mt Ida Formation,

Notoparmella plentiensis Assemblage Zone, late Ludlow. The age of

the Mclvor Sandstone is constrained by early Ludlow (upper nilssoni

Biozone) graptolite assemblages from the underlying Melbourne

Formation (Rickards and Sandford, 1998). In Europe, Homalonotus

occurs in abundance in strata of Ludfordian age, occurring rarely in the

Gorstian (Thomas et al., 1989) and possibly ranging into the Pr idoli.

The first appearance of H. talenti about 380 m above the base of the

Mclvor Sandstone (at PL2265) is considered here to approximate the

Gorstian-Ludfordian boundary. The Ludlow-Pridoli boundary can be

placed within the interval between the last appearance of talenti (at

PL2239) and the first appearance of the post-Ludlow brachiopod

Cyrtina at a slightly higher horizon, 50-100 m above the base of

Cornelia Member.

Derivation of name. For John A. Talent (Macquarie

University), for his contribution to Victorian palaeontology.

Diagnosis. Glabella trapezoid, sides straight and converging at

20°, anterior margin broadly rounded. Glabellar length about

1.1 times preoccipital glabellar width and 0.94 times cranidial

length. Preglabellar furrow very deeply impressed. Eye placed

with midline of palpebral lobe opposite 0.56 glabellar

length/0.52 cranidial length. Dorsal surface of rostral plate 0.14

times cephalic length. Hypostome with length 0.85 width, lobes

on the posterior border with length 0.17 times hypostomal

length. Pygidium with length about 0.9 times width, postaxial

ridge projecting posteriorly, tip rounded. Pygidial axis with

width 0.5 times pygidial width, 11 axial rings. Axial furrows

straight and tapering at about 30°. 7 pleural ribs, rib-ring

medially offset at fourth rib. Ring, pleural and axial furrows

shallow to moderately impressed.

Description. Exoskeleton of moderate size, maximum length estimat-

ed 12 cm (from NMV P305923), occipital convexity (tr.) moderate,

pygidial convexity (tr.) strong.

Cephalon wide, length 0.6 times width, with trapezoid outline, sides

moderately convex and converging forwards at about 75°, anterior

margin tricuspate, median cusp triangular in outline with rounded tip,

length about 0.6 times width, lateral cusps with obtusely angled tips

reaching forward to midlength of median cusp. Cranidial width 1.9

Figure 9. Homalonotus talenti sp. nov. la, holotype NMV P304936, cephalon, dorsal view X 3.0 (latex cast) from PL6650. lb, same, x 2.6 (inter-

nal mould), lc, same, lateral view x 3.0 (latex cast). 2, paratype NMV P304938, cephalon, dorsal view x 2.6 (latex cast) from PL6650. 3, paratype

NMV P304929, cranidium, dorsal view x 2.1 (internal mould) from PL6650. 4, paratype NMV P304923, cranidium, dorsal view x 1.65 (internal

mould) from PL6650. 5a, paratype NMV P304927, cephalon, dorsal view x 5.5 (internal mould) from PL6650. 5b, same, anterior view x 5.0.

6, paratype NMV P304937, cephalon, dorsal view x 1 .9 (latex cast) from PL6650. 7, paratype NMV P304924, cranidium, dorsal view x 3.6 (inter-

nal mould) from PL6650. 8a, paratype NMV P304939, cephalon, dorsal view x 2.0 (internal mould) from PL6650. 8b, same, x 2.1 (latex cast).

9, paratype NMV P304943, librigena, dorsolateral view x 1.22 (latex cast) from PL6650. 10, paratype NMV P304925, cranidium, dorsal view

x 1.75 (internal mould) lfom PL6650. 11, paratype NMV P304928, cranidium, dorsal view x 1.6 (internal mould) from PL6650. 12, paratype

NMV P304949, thoracic segment, lateral view x 1.75 (internal mould) from PL6650. 13, paratype NMV P304945, thoracic segment, dorsal view

x 1.4 (internal mould) from PL6650. 14, paratype NMV P304941, librigenal doublure, ventral view x 2.4 (latex cast) from PL6650. 15, paratype

NMV P304947, hypostome, ventral view x 2.2 (internal mould) from PL6650. 16a, paratype NMV P304946, hypostome, ventral view x 3.4 (latex

cast) from PL6650. 16b, same (internal mould). 17a, paratype NMV P304948, hypostome, ventral view x 3.5 (internal mould) from PL6650. 17b,

same (latex cast).

Homalonotid trilobites from the Silurian and Lower Devonian

Andrew C. Sandford

Homalonotid trilobites from the Silurian and Lower Devonian

times length. Glabella with anterior margin strongly defined, arc of

curvature centred at about glabellar midlength. Occipital ring about 0.1

times cranidial length, slightly wider medially. Occipital furrow mod-

erately impressed to shallow, with weak forward flexure medially.

Glabellar lobation extremely weak (best seen on NMV P304928) to

indistinct. LI 0.32 times glabellar length, L2 0.12 times glabellar

length, L3 0.10 times glabellar length and frontal lobe 0.20 times

glabellar length. SI weakly convex, directed diagonally abaxially. S2

and S3 transverse. Axial furrows shallow to moderately impressed.

Paraglabellar area very weakly defined. Length (sag.) of preglabellar

furrow and ridge-like preglabellar field 0.03 times cranidial length.

Length (exsag.) of posterior border equal to occipital length adaxially,

lengthening slightly abaxially. Posterior border furrow transverse, very

wide and shallow, meeting lateral border furrow distally. Postocular

fixigenal area long, length (exsag.) 0.25 times cranidial length.

Palpebral lobes placed anteriorly and remotely (6-6 1.5 times preoc-

cipital glabellar width). Palpebral lobe length (exsag.) 0.15 times

cranidial length, palpebral furrow indistinct. Preocular fixigenal area

of moderate width, width 0.17 5-6 adjacent to palpebral area, eye

ridges not distinct, narrowing markedly anteriorly. Anterior branches

of facial suture converging at about 80°, curving inwards opposite the

antero-lateral corner of the glabella and converging at about 140°

anteriorly. Librigena with wide, moderately impressed border furrow,

not continuing forward of antero-lateral comer of glabella, librigenal

field weakly convex, steeply inclined, lateral border wide, convex. Anter-

ior margin of librigena projecting far forwards from juncture of rostral,

connective and facial sutures at cephalic margin as triangular cusp.

Course of rostral suture broadly rounded, concentric to anterior

margin of glabella. Dorsal surface of rostral plate rounded triangular,

length (sag.) 0.4 times width, strongly concave (tr. sect.). On cephalic

doublure connective sutures straight and weakly converging posterior-

ly. Librigenal doublure without distinct vincular furrow, strongly con-

vex (exsag. sect.) adjacent to connective suture (i.e. accommodating

preglabellar furrow). Hypostomal suture very broadly rounded.

Hypostome with middle furrow shallow to moderately impressed,

anterior wing process small (width 0. 1 times hypostomal width), lobes

on posterior border parabolic in outline, deep medial notch with sides

converging at about 75°.

Thorax with axial furrows poorly defined. Pleural furrows narrow

(exsag.) and deep, pleural tips rounded.

Pygidium with triangular outline, sides weakly convex and con-

verging at about 80°. In lateral view pygidium high, height equal to

length. Pygidial axis reaching to about 0.8 times pygidial length, con-

tinuous posteriorly with wide postaxial ridge. Postaxial ridge raised,

parallel-sided, wide, width (tr.) 0.45 times axial width, posterior mar-

gin with parabolic outline. Axial furrows tapering, curving to the

exsagittal posteriorly, shallow anteriorly, moderately impressed poster-

iorly. Pleural furrows shallowing markedly adjacent to border furrow.

Border furrow moderately impressed opposite pleural field, shallow

opposite postaxial ridge. In dorsal view border narrow (tr.) but pro-

tuberant from margin of pleural field. In lateral view border very wide

anteriorly, merging with wide articulating facet, narrowing markedly

posteriorly. Lateral border continuous with narrow pygidial doublure.

In posterior view anterior margin of pygidium strongly convex, poster-

ior margin with distinct medial and lateral arches. In ventral view,

inner margin of doublure parabolic in outline with deep medial inden-

tation.

Dorsal exoskeleton finely granulose. Pygidial border with fine ridging.

Discussion. Holloway and Neil (1982) suggested the affinities of an

incomplete cephalon examined by them were with Homalonotus. Their

suggestion is confirmed with the additional specimens listed. They

noted similarities between the associated pygidium and that of the

South American Lower Devonian species H. clarkei, but these similar-

ities are superficial. Following Cooper (1982), and as discussed below,

clarkei is assigned to Burmeisteria.

Hypostomes are also known for Homalonotus knightii and H.

rhinotropis (Salter, 1865: pi. 12 fig. 10; Angelin, 1878: pi. 20 fig. lc).

The hypostome of H. talenti most closely resembles that of the type

species. The hypostome of rhinotropis is relatively elongate (length

times 1.1 width) compared to that of knightii (length 0.81 times width)

and talenti (length 0.85 times width). The projections of the posterior

margin are broadly based and long in talenti and knightii, but short in

rhinotropis.

Although the ventral surface of the rostral plate of Homalonotus tal-

enti is not known, the course of the connective sutures (indicated by

the shape of the librigenae) is more or less straight and slightly con-

vergent posteriorly, indicating the rostral plate to be approximately

pentagonal, with subequal sides. Apparent curvature of the connective

sutures on Fig. 9.14 is due to the oblique orientation of the specimen.

The broad, rounded medial indentation of the inner margin of the

pygidial doublure of Homalonotus talenti (Fig. 10.7e) differs from that

of H. knightii, in which the margin is more or less straight laterally, and

defines an acute angle medially (see Salter, 1865: pi. 12 fig. 9a,

Tomczykowa, 1975: pi. 1 fig. 5c).

Environmental notes. Throughout its range Homalonotus talenti occurs

in thick-bedded fine- to medium-grained sandstones, in low diversity

or monospecific assemblages. At the type locality where the species

occurs in greatest abundance the proportion of articulated specimens is

low (6%) and the proportion of broken specimens low (3%).The fauna

can be assigned to taphofacies Til and indicates shallow environments

around normal wave base.

Homalonotus williamsi sp. nov.

Figures 10.1-10.4

Type material. Holotype NMV P308674 (cephalon) from PL6615,

Jutson locality VII, Eden Park, Victoria (Fig. 10.1). Paratypes NMV

P308675 (pygidium), NMV P308676 (cephalon) from PL6615.

Paratype NMV P304511 (pygidium) from PL6614, Jutson locality VI,

Eden Park. For localities see Fig. 1 1 .

Figure 10.1-10.4 Homalonotus williamsi sp. nov. la, holotype NMV P308674, cephalon, dorsal view x 2.1 (internal mould) from PL6615. lb,

same, anterior view, lc, same, oblique view x 2.3 (latex cast). Id, same, dorsal view. 2a, paratype NMV P308676, cranidium, dorsal view x 1.3

(internal mould) from PL6615. 2b, same, lateral view x 1.2. 2c, same, anterior view x 1.3. 3, paratype NMV P308675, pygidium, oblique view

x 3.0 (latex cast) from PL6615. 4a, paratype NMV P304511, pygidium, oblique view x 1.35 (internal mould) from PL6614. 4b, same, dorsal view

x 1.45.

Figure 10.5-10.11, Homalonotus talenti sp. nov. 5a, paratype NMV P304952, pygidium, dorsal view x 1.1 (latex cast) from PL6651. 5b, same,

posterodorsal view. 6, paratype NMV P304953, pygidium, oblique view x 1.2 (latex cast) from PL6651. 7a, paratype NMV P304921, pygidium,

lateral view X 1.6 (internal mould) from PL6650. 7b, same, dorsal view. 7c, same, posteroventral view. 7d, same, posterior view. 7e, same,

ventral view (doublure). 8a, paratype NMV P304917, pygidium, posteroventral view x 1.2 (internal mould) from PL6650. 8b, same, dorsal view

x 1.6. 8c, same, lateral view x 1.4. 9, paratype NMV P304918, pygidium, dorsal view x 2.6 (latex cast) from PL6650. 10, paratype NMV P304920,

pygidium, lateral view x 2.7 (internal mould) from PL6650. 11, paratype P304922, pygidium, dorsal view x 1.5 (internal mould) from PL6650.

Andrew C. Sandford

Figure 11. Geological sketch map of the Springfield- Kinglake West area showing Llandovery -Lochkovian fossil localities yielding homalonotids.

For other fossil localities see also Jutson (1908, pi. 3), Thomas (1960), Talent (1964, fig. 1), Williams (1964, fig. 2), Garratt (1972, 1977), Rickards

and Sandford (1998, fig. 6), Sandford (2002, fig. 1C; 2005, figs 2-3).

Other material. NMV P304512 from PL6614.

Stratigraphic distribution. Macropleura band, Eden Park Formation

(130-140 metres above base of unit), lowermost Notoparmella

plentiensis Assemblage Zone, early-mid Ludlow.

Derivation of name. For George E. Williams, for his contri-

bution to Victorian stratigraphy.

Diagnosis. Cephalon wide, length 0.6 times width. Glabella

long, length 1.15 times width, sides more or less straight, taper-

ing at about 15°, anterior margin broadly rounded, arc centred

at 0.55 glabellar length. Glabellar length 0.92 times cranidial

length. Glabellar lobation distinct, SI and S2 expressed as deep

notches adjacent to the axial furrows but very shallow abax-

ially, placed opposite 0.43 and 0.63 glabellar length respec-

tively. Axial furrows moderately impressed on internal moulds

(shallow on external moulds), preglabellar furrow very deeply

impressed. Rostral plate with length of dorsal surface 0.11

times cephalic length, width (across rostral suture) 1.9 times

Homalonotid trilobites from the Silurian and Lower Devonian

length, triangular. Genae moderately swollen, lateral border

furrow moderately impressed. Eye placed with midline of

palpebral lobe opposite 0.67 glabellar length. Anterior branch

of facial suture with posterior section straight and strongly con-

vergent (at about 90°), anterior section evenly curving to the

transverse. Rostral suture weakly convex. Pygidium triangular

in outline, sides straight, converging posteriorly at about 100°.

Axial furrows moderately impressed. Pygidial axis strongly

convex, raised, sides converging at about 25°, continuous pos-

teriorly with wide postaxial ridge. Pleural field with 7 ribs.

Pleural and ring furrows moderately impressed, of subequal

depth.

Discussion. Homalonotus williamsi closely resembles

H. talenti from the lower Ludlow-lower Pndolf strata of the

Heathcote area. Differences in cephalic morphology are subtle,

but talenti can be distinguished in that the glabella is less elon-

gate (glabellar length 1.1 times width) SI -S3 are extremely

weakly impressed to indistinct, the axial furrows are much

shallower, the preglabellar furrow and preglabellar field are

notably shorter (exsag. and sag., glabellar length 0.95 times

cranidial length), the eyes are more posteriorly placed (midline

of palpebral lobe opposite 0.55 glabellar length), and the rostral

process is wider posteriorly and only weakly convex down-

wards. The pygidium of williamsi is known only from frag-

ments, but differs from that of talenti in having deeper axial,

ring and pleural furrows.

In addition to the pygidial characters and the very deep,

trench-like preglabellar furrows distinguishing the two

Australian species from the northern-hemisphere species,

Homalonotus talenti and H. williamsi also share straight and

strongly convergent anterior branches of the facial sutures, in

contrast to the convex outwards course of the sutures in

H. knightii, H. dawsoni and H. rhinotropis. The Australian

species and rhinotropis share a rounded anterior glabellar

margin, differing from the transverse margin of knightii and

dawsoni.

Environmental notes. See Dipleura garratti sp. nov.

Brongniartella Reed, 1918

Type species. Homalonotus bisulcatus Salter, 1851 from the Upper

Ordovician of England, by original designation.

Brongniartella sp.

Trimerus sp. — Holloway and Sandford, 1993: 93, fig. 4L, non figs

4C-D, 4F-G, 41- J, 4N-P.

Material. NMV PI 37228 (pygidium, figured Holloway and Sandford,

1993: fig. 4L) from PL359, Tiger Range, northwest of Maydena,

Tasmania. For locality see Holloway and Sandford: fig. 1 .

Stratigraphic distribution. Richea Siltstone, Monograptus

griestoniensis-M. crenulata biozones, upper Llandovery.

Notes. The elongate, rounded parabolic outline of the pygid-

ium, the strongly raised, narrow, convex pygidial axis and the

indication of a distinct border suggest assignment to

Brongniartella. The concave sides of the axis is shared with

other species of Brongniartella. The species is a late appear-

ance for Brongniartella, a predominantly Upper Ordovician

genus but known to extend into the Lower Llandovery atavus-

cyphusl biozones in Britain (Temple, 1975) and also recorded

from the Lower Llandovery of Jordan (Wolfart et al., 1968).

The Upper Llandovery Tasmanian record narrows the gap

between Lower Llandovery Brongniartella and the youngest

known species, B. pamiricus (Balashova, 1966) from the

Wenlock of Pamir, central Asia.

Digonus Giirich, 1909

Type species. Homalonotus gigas Roemer, 1843, from the Lower

Devonian (Emsian) Kahleberg Sandstone, Germany, by original

designation.

Other species and subspecies included. Burmeisteria ( Digonus )

antarcticus Saul, 1965, D. armoricanus Pillet, 1961a, D. asturco

Kegel, 1927, Homalonotus crassicauda Sandberger and Sandberger,

1849, D. gigas posterior Wenndorf, 1990, H. goniopygaeus

Woodward, 1882, H. (D.) harpyius Richter and Richter, 1932, H. inter-

medius Vietor, 1919, H. laticaudatus Williams and Breger, 1916,

H. (D.) ornatus disornatus Richter and Richter, 1932, D. ornatus

linguatus Wenndorf, 1990, H. ornatus Koch, 1883a, D. comes

Chlupac, 1981, H. roemeri de Koninck, 1876, D. wenndorfi sp. nov.,

Trimerus zeehanensis Gill, 1949, D. zemmourensis Pillet, 1961b,

Digonus sp. A in Wenndorf (1990).

Other species tentatively included. Digonus collini Renaud, 1942,

Homalonotus derbyi Clarke, 1890.

Range. Lochkovian-Emsian.

Diagnosis. Cranidium trapezoidal in outline, anterior margin

with median cusp. Dorsal section of connective sutures very

short. Glabella trapezoidal in outline, sides straight or very

weakly concave. Glabellar lobation very weak or absent.

Paraglabellar area distinct. Anterior outline of cranidium

quadrate, anterior branches of facial suture more or less straight

between palpebral lobe and midlength of preglabellar field and

converging at an acute angle (20-60°), curving abruptly to the

transverse anteriorly. Rostral suture transverse to weakly con-

cave. Ventral surface of rostral plate with thorn, spine or keel.

Pygidium triangular to elongate triangular, with wide axis

(0.5-0.7 times pygidial width). Axis with weak independent

convexity (tr. sect.), postaxial ridge not raised. Pleural and ring

furrows deep to very deep, more or less equal in depth. Axial

furrow shallow or moderately impressed posteriorly, very shal-

low or effaced anteriorly, anteriormost ribs and rings fused,

with corresponding section of axial furrow effaced or reduced

to shallow invagination in posterior margin of segment. Pleural

furrows maintaining uniform depth to a point close to border.

Border furrow and border poorly defined. Rib-ring offset high

(fifth-seventh rib).

Discussion. Previous diagnoses for Digonus are brief. Giirich

(1909) listed the truncate and indented outline of the cephalic

anterior margin, the angular margin of the antero-lateral corners

of the cranidium, the pointed pygidial tip and the weakly

tapered, trapezoid glabellar outline. Reed (1918) emphasised

the strong expression of the pygidial segmentation as a further

diagnostic character. Sdzuy (1959) included the absence of

glabellar lobation and angular pleural tips as diagnostic charac-

ters although, as he regarded Digonus as a subgenus of

Burmeisteria, other characters were incorporated into the

Andrew C. Sandford

generic concept. These included the distinct paraglabellar area,

the presence of a ventral process on the rostral plate, a triangu-

lar pygidial outline, distinct pygidial trilobation, and a poorly

expressed postaxial ridge. Tomczykowa (1975) omitted many

of Sdzuy’s characters from her revised diagnosis, closely fol-

lowing Reed. In emending Tomczykowa’s diagnosis, Wenndorf

(1990) noted the presence of weak glabellar lobation in some

species, and that early representatives of the genus have less

elongate pygidial outlines.

The revised diagnosis given here adds substantially to the

list of diagnostic characters and qualifies other characters pre-

viously used. A substantially restricted concept of the genus is

proposed by placing new emphasis on pygidial characters

including the relative depth of pygidial ring and pleural

furrows, the expression of the axial furrows, the expression of

the postaxial ridge and the width and convexity of the pygidial

axis. The revised diagnosis emphasises differences between

Digonus, Trimerus and Burmeisteria, and results in sub-

stantially different assignments of the species listed by

Tomczykowa (1975) and Wenndorf (1990).

Tomczykowa (1975) and Wenndorf (1990) considered

Digonus to have been derived from Trimerus. The genera are

certainly close, many of the characters listed in the diagnosis of

Digonus occurring variously in species of Trimerus. Although

the presence of a rostral keel or process is considered of pri-

mary importance in differentiating the genus from Trimerus, it

is the combination of characters that defines Digonus. Other

cephalic characters, particularly the degree of glabellar loba-

tion, the quadrate course of the facial and rostral sutures, and

the trapezoid glabellar outline, distinguish Digonus from most

species of Trimerus. Pygidia of Digonus can generally be dis-

tinguished from those of Trimerus by the deeper pleural and

ring furrows that are more or less equal in depth, by the

shallower axial furrows, and by the less convex axis and

postaxial ridge. For the morphologically convergent species, it

is the continuity of the axial furrow anteriorly in Trimerus (and

the fusion of the anteriormost axial ring and pleural rib in

Digonus) that distinguishes the genera. Hence, Homalonotus

crassicauda from the Emsian of Germany, known only from

pygidia and previously interpreted as a temporally disjunct

representative of Trimerus (Wenndorf, 1990, Schraut, 2000)

clearly belongs in Digonus. The Lochkovian North American

H. major Whitfield, 1881 is best assigned to Trimerus rather

than to Digonus, because the pygidial axial furrow is deep and

distinct anteriorly.

Digonus wenndorfi and D. zeehanensis from the lower

Lochkovian of south-eastern Australia are the best known of

the early representatives of Digonus and support the derivation

of this genus from Trimerus. D. wenndorfi and the French

D. roemeri are the earliest Digonus, occurring immediately

above the Silurian-Devonian boundary and suggesting a latest

Silurian origin for the genus. In cranidial features, wenndorfi

and zeehanensis show close affinities to the D. omatus group

from the middle Pragian-Emsian of Europe rather than to the

D. gigas group (see Wenndorf, 1990) whose members share

longer preglabellar fields. Weak glabellar lobation and short

pygidia with markedly obtuse (120-130°) angular tips set

wenndorfi and zeehanensis apart from later members of the

genus, with the exception of several species (D. antarcticus and

D. omatus disornatus ) that retain weak lobation, and several

others that have similarly short pygidia (e.g. D. armoricanus

and D. crassicauda ). In addition to weak glabellar lobation and

short pygidial proportions, wenndorfi also exhibits a moder-

ately raised pygidial postaxial ridge (Figs 12.6, 12.12-12.18).

In these features wenndorfi can be considered a ‘primitive’

Digonus, with relict features of Trimerus retained. D. zeehan-

ensis bears a short (sag.) but wide (tr.) median cephalic cusp

(Fig. 13.1) intermediate in morphology between the large semi-

circular cusps of Trimerus on species such as T. ( Ramiotis ) otisi

and T. ( Trimerus ) johannis, and the small, acute cusps of

Emsian Digonus. The anteriorly distinct pygidial axial furrows

of roemeri (see Morzadec, 1986: pi. 32 figs 1, 4, 6-7) and (to a

lesser extent) wenndorfi, can also be interpreted as a Trimerus-

like feature, although the wide pygidial axis and equally deep

pleural and ring furrows indicates their affinities with other

Digonus.

Emphasising the significance of the transverse anterior

margin of the cranidium and the depth of the pygidial pleural

and ring furrows, Tomczykowa (1975) derived Digonus from

Trimerus, suggesting T. ( Trimerus ) johannis as a transitional

morphology between the genera. Thomas (1977) doubted this

suggestion, emphasising the difference in age between T. (T.)

johannis (late Wenlock) and the first appearance of Digonus

(earliest Lochkovian). Wenndorf (1990) interpreted European

Lochkovian species such as Homalonotus vialai Gosselet in

Gosselet et al., 1912 and H. roemeri as representing early

Digonus morphologies, noting similarities to the Polish Ludlow

T. permutus Tomczykowa, 1978 (=T. lobatus Tomcykowa,

1975 non Prouty, 1923 in Swartz and Prouty). A more plausible

transitional morphology is represented by the upper Ludlow

T. ( Ramiotis ) otisi. The similarities of this species to contem-

porary Homalonotus have been discussed above, but its

similarities to species of Digonus are more marked. In addition

to having a tricuspid cephalic margin, otisi exhibits a sub-

quadrate course of the facial and rostral sutures, weak glabellar

lobation, straight- sided glabellar outline, deep pleural and

equally deep ring furrows, and a pygidial axial furrow that is

indistinct anteriorly (Fig. 20). In the latter feature, otisi is an

exception amongst congeners. However, the flat rostral plate,

the long glabellar proportions, the narrow proportions of the

pygidial axis and the raised postaxial ridge demonstrate its

close affinities to Trimerus.

Digonus wenndorfi and D. zeehanensis demonstrate the con-

servative Digonus cephalic morphology to have been already

established in the earliest Lochkovian. European species con-

sidered by Tomcykowa (1975) as representing early Digonus

morphologies, including Homalonotus vialai, D. bostoviensis

and D. elegans, are variably assigned below to Paraho-

malonotus and Wenndorfia, and exhibit few of the diagnostic

cephalic or pygidial features of Digonus. In particular, the

anterior branches of the facial sutures of these species are

broadly curved and converge at a strongly obtuse angle

opposite the preglabellar field, giving the anterior margin of

the cranidium a more rounded/parabolic outline. Burmeisteria

( Digonusl ) delattrei Pillet and Waterlot, 1982 from the Emsian

of France exhibits few features typical of Digonus. It has a

Homalonotid trilobites from the Silurian and Lower Devonian

raised pygidial axis, a raised postaxial ridge with a posteriorly

projecting spine, anteriorly distinct axial furrows and a

moderately convex (tr.), elongate glabella. The pygidial

morphology, including the posteriorly projecting axis, indicates

assignment to Burmeisterella. Wenndorf (1990) questionably

assigned the Brazilian Homalonotus oiara Hartt and Rathbun,

1875 to Digonus, but their emphasis on the concavity of

the sides of the glabella is not compatible with the quadrate

glabellar outline considered here as diagnostic of Digonus.

The forward eye position exhibited by the single cranidium

known suggests affinities with Burmeisteria rather than

with Dipleura.

Relationships between Digonus and Burmeisteria have been

variously interpreted. Sdzuy (1959) considered Digonus to

be a subgenus of Burmeisteria. Tomczykowa (1975) listed

several differences between the taxa, emphasising the

absence of spines and glabellar lobation in Digonus to support

its independent status. Cooper (1982) argued that the range of

variation in the course of the rostral suture, the degree

of glabellar lobation and the glabellar outline in the highly

polymorphic type species B. herschelii (Murchison, 1839)

overlapped with morphologies typical of Digonus. Following

the emphasis placed by Sdzuy on these characters, Cooper

regarded Digonus as junior synonym of Burmeisteria.

Wenndorf (1990) questioned many of the differences listed

by Tomczykowa, noting a convergence in morphologies

between Burmeisteria and Digonus, but nevertheless main-

taining their independent status. Kennedy (1994) noted that

the pygidial doublure of Digonus, unlike that of Burmeis-

teria, is often narrower and bears a narrow groove in the

margin of the pygidial doublure. This distinction between the

genera also applies to Burmeisterella, which Kennedy consid-

ered as a junior synomym of Burmeisteria. The independent

status of Burmeisterella is supported here, with high

generic significance accorded to the very short (sag.) pre-

glabellar field and the morphology of the pygidial axis,

which is raised high rather than fused with the pleural field

posteriorly, and extends posteriorly over the margin as a

narrow-based to spinose tip. In addition, the pygidium of

Burmeisterella has a more convex lateral margin, and

always bears a pair of prominent, large nodes or spines on the

anteriormost pleural rib. The independent status of Bur-

meisteria and Digonus is supported in this work. The taxa can

be readily distinguished morphologically, despite the extreme

polymorphism exhibited by herschelii. In Burmeisteria, the

pygidial axial furrow is impressed anteriorly, and the

pygidial pleural and ring furrows are typically shallower than

those of Digonus and shallow posteriorly. Burmeisteria is

further characterised by a high number of pygidial segments

(>13 axial rings). Cranidia of Burmeisteria and Digonus may

exhibit morphological convergence, but a glabellar outline

markedly expanded across LI -LI (tr.) or with concave sides,

and well defined lateral glabellar furrows immediately

distinguish Burmeisteria when present.

Following Hennig (1965), Wenndorf suggested that the

mutually exclusive palaeogeographic ranges of Burmeisteria

and Digonus represented a significant taxonomic feature

supporting their independent status. Digonus wenndorfi.

D. zeehanensis and D. antarctica extend the range of the genus

into temperate palaeolatitudes of north-eastern Gondwana.

However, the palaeogeographic ranges of the genera remain

mutually exclusive. B. herschelii is restricted to lower palaeo-

latitudes of southern Gondwana, occurring in southern Africa,

the Falkland Islands and South America. The reassignment of

several South American taxa to Burmeisteria emphasises the

provincialism of the genus (see Table 1), perhaps as early as the

Late Silurian. Homalonotus linares Salter, 1861, assigned

below to Burmeisteria (see Trimerus) occurs in the Late

Silurian of Bolivia and Uruguay.

Affinities of the Lochkovian Homalonotus noticus Clarke,

1913 (?= H. caorsi Mendez-Alzola, 1938) from South America

and possibly South Africa (see Cooper, 1982) are with

Burmeisteria. Reed (1918) initially assigned the species to

Burmeisteria but later reassigned it to Digonus (Reed, 1925).

Sdzuy (1957) suggested that the species represents a transi-

tional form between Burmeisteria and Digonus. The distinct

S1-S3, the narrow pygidial axis and the anteriorly continuous

pygidial axial furrow are incompatible with assignment to

Digonus. Tomczykowa (1975) and Wenndorf (1990) assigned

H. noticus to Trimerus, but the presence of a rostral projection,

a sinusoidal rostral suture and high pygidial segmentation (up

to 13 axial rings) excludes the species from the genus as

defined here.

Homalonotus clarkei from the Lower Devonian South

America (?= H. buqueti Mendez-Alzola, 1938, ?= H. spat-

ulirostris Mendez-Alzola, 1938), has been variably assigned to

Digonus (Wolfart, 1968), to Trimerus (with question,

Tomczykowa, 1975), to Burmeisteria (Cooper, 1982) and to

Dipleura (Wenndorf, 1990). The strongly folded anterior

cephalic margin excludes assignment to Trimerus, as this taxon

is characterised in this work by having a flat rostral plate. The

very shallow pygidial pleural furrows and somewhat deeper

ring furrows of clarkei are typical of Dipleura, but the tricuspid

anterior cephalic margin, the quadrate and medially concave

anterior cranidial margin, and the strong forward tapering of the

glabella do not conform to this assignment. The weakly

expressed pygidial segmentation excludes the species from

Digonus as defined here. The generic affinities of the species

are uncertain.

Burmeisteria ( Digonus ) accraensis from the Devonian of

Ghana exhibits weak pygidial furrows, excluding the species

from Digonus as defined in this work. The taxon has been vari-

ably assigned to Trimerus (Tomczykowa, 1975) and to Dipleura

(with question, Wenndorf, 1990), but the presence of a rostral

process (see Saul, 1967: pi. 143 fig. 6) excludes the species from

these genera.. The species is assigned here to Burmeisteria.

Digonus wenndorfi sp. nov.

Figs 3, 12, 22.1-22.6

Trimerus ( Dipleural ) sp. — Talent, 1964: 49 (pars), pi. 26 figs 1, 2

non text-fig. 6.

Homalonotidae gen. et sp. indet. 1. — Holloway and Neil, 1982: 145,

figs 4A-H.

Type material. Holotype NMV P304717 (pygidium) from PL2203,

Thomas locality F3, Parish of Dargile, Heathcote, Victoria (Fig.

Andrew C. Sandford

Homalonotid trilobites from the Silurian and Lower Devonian

12.17). Paratypes NMV P304709-P304716 (cranidia), NMV P304874

(librigena), NMV P304872, P304872 (thoracic segments), NMV

P304717, NMV P304860-P304866, NMV P304868 (pygidia) from

PL2203. Paratype NMV P304913 (librigena) from PL2327, Heathcote.

For localities see Fig. 8.

Previously figured material. NMV P78295 (ex GSV 39474, pygidium,

figured Holloway and Neil, 1982: figs 4E, 4H), NMV P59656 (ex GSV

39200 pygidium, figured Talent, 1964: pi. 26 fig. 2, Holloway and

Neil, 1982: figs 4F, 4G), NMV P59655 (ex GSV 39476, pygidium, fig-

ured Talent, 1964: pi. 26 fig. 1) from PL2203. NMV P78293 (thoracic

segment, figured Holloway and Neil, 1982: fig. 4C), NMV P78294

(thoracic segment, figured Holloway and Neil, 1982: fig. 4D) from

PL2202, Thomas locality F2, Parish of Dargile, Heathcote. NMV

P78292 (cephalon, figured Holloway and Neil, 1982: figs 4A, 4B)

from PL2204, Thomas locality F4, Parish of Dargile, Heathcote. For

localities see Fig. 8.

Registered material. 88 specimens: 2 cephala, 12 cranidia, 4 librigenae,

17 thoracic segments, 53 pygidia. NMV P59655, P59656, NMV

P78295, NMV P82882, NMV P82886, NMV P304709-P304717,

NMV P304859-P304903 from PL2203. NMV P78293, P78294, NMV

P82880, NMV P82883-P82885, NMV P304904 from PL2202. NMV

P82941, NMV P304905-P3049 14 from PL2327. NMV P78292 from

PL2204.

Stratigraphic distribution. Mt Ida Formation, from about 400 m above

the base of the Dealba Member up to about the 100 m above the base

of the Stoddart Member, Boucotia janae Assemblage Zone, early

Lochkovian. The first appearance of Digonus wenndorfi at PL2204 is

close stratigraphically to the first appearance of Boucotia (see Garratt,

1983: fig. 7) and together support a basal Lochkovian age for these

horizons.

Derivation of name. For Dr Klaus-Werner Wenndorf

(Germany), for his contribution to the study of homalonotids.

Diagnosis. Glabella trapezoid, length 1.0- 1.2 times width, sides

straight and converging at about 20° opposite genae, anterior

margin of glabella well defined with medial indentation

moderately impressed to indistinct. Glabellar lobation weak to

indistinct. Axial furrows moderately impressed opposite genae.

Palpebral lobe short, 0.1 times cranidial length, placed with

midline opposite 0.5 glabellar length/0.39 cranidial length.

Preglabellar field long, length (sag.) 0.22 times cranidial

length. Rostral suture transverse. Pygidium triangular, sides

moderately convex and converging posteriorly at 85-100°, tip

angular. Pygidial axis with width 0.5-0.6 times pygidial width,

11-12 axial rings, ring furrows deep, continuous with raised

postaxial ridge. Axial furrows poorly defined opposite

first-second axial rings, moderately impressed posteriorly,

straight and tapering at 30-40°. Pleural furrows deep. 8-9

pleural ribs, rib-ring medially offset at fifth rib.

Description. Exoskeleton large (maximum length estimated 25 cm

from NMV P304860), occipital convexity (tr.) moderate, pygidial

convexity (tr.) strong. Dorsal exoskeleton finely granulose.

Cranidia with elongate and short forms. Elongate form with

cranidial width about 1.6 times length, short form with cranidial

width about 1.9 times length. Glabella with length 0.78 times cran-

idial length, anterior margin very broadly rounded to transverse.

Elongate form with glabellar length 1.2 times width, short form with

glabellar length equal to width. Occipital ring with length 0.1 times

glabellar length. Occipital furrow deeply impressed, with weak for-

ward flexure medially. Glabellar lobation (best seen on NMV P304715

and NMV P304710) with LI 0.28 and L2 0.15 times glabellar length

respectively. SI straight and directed posteromedially at about 17°

from the transverse, S2 weakly convex forwards and transverse, S3

indistinct. In some specimens (e.g. NMV P304710, P304711) SI mod-

erately impressed for short distance adjacent to axial furrow. Axial

furrows very shallow and directed diagonally opposite occipital ring.

Paraglabellar area weakly defined (best seen on NMV P304711).

Length (exsag.) of posterior border equal to occipital length adaxially,

lengthening slightly abax-ially. Posterior border furrow transverse,

very wide, moderately impressed, terminating distally. Postocular fix-

igenal area very short, length (exsag.) 0.16 times cranidial length.

Palpebral lobes placed remotely (5-6 1.67 times preoccipital glabellar

width/0.7 times cranidial width). Palpebral furrow weak to moderately

impressed. Preocular fixigenal area of moderate width, 0.17 times 5-6

narrowing slightly anteriorly. Preglabellar field weakly concave (tr.

sect.). Anterior branches of facial suture angular, directed exsagittaly

for a short distance adjacent to the eye (to a point opposite 0.7 glabel-

lar length), anteriorly converging at about 40° in elongate forms

and 60° in short forms. Librigena without distinct border furrow or

lateral border. In anterior view anterior margin of librigenae

moderately convex.

Thorax with axial furrows indistinct. Pleural furrows wide and

deep.

Pygidia with long form and narrow form, sides converging poster-

iorly at about 85° in narrow form and 100° in wide form. Pygidial axis

with width about 0.5 times pygidial width in wide form, 0.6 in narrow

form. Pygidial axis reaching to about 0.85 times pygidial length,

raised, continuous posteriorly with postaxial ridge. Postaxial ridge

wide, width 0.3 times axial width. Axial furrows straight and tapering

at about 33° in narrow form, 38° in wide form, curving to the exsagit-

tal posteriorly. Pleural furrows not reaching margin. Border furrow and

border not defined. In posterior view posterior margin of pygidium

Figure 12. Digonus wenndorfi sp. nov. 1, paratype NMV P304715, cranidium, dorsal view x 1.25 (internal mould) from PL2203. 2a, paratype

NMV P304714, cranidium, dorsal view x 1.6 (internal mould) from PL2203. 2b, same (latex cast). 3a, paratype NMV P304709, cranidium,

dorsal view x 0.75 (internal mould) from PL2203. 3b, same, lateral view. 3c, same, dorsal view (latex cast). 4, paratype NMV P304716, cran-

idium, dorsal view x 1.2 (internal mould) from PL2203. 5a, paratype NMV P30471 1, cranidium, dorsal view x 1.75 (internal mould) from PL2203.

5b, same (latex cast). 5c, same, oblique view (internal mould). 6, paratype NMV P304868, pygidium, dorsal view x 1.0 (internal mould) from

PL2203. 7a, paratype NMV P304872, thoracic segment, lateral view x 2.3 (internal mould) from PL2203. 7b, same, dorsal view. 8, paratype NMV

P304874, librigena, ventral view (doublure) x 1.75 (latex cast) from PL2203. 9, paratype NMV P304913, librigena, lateral view x 1.7 (internal

mould) from PL2327. 10, paratype NMV P304873, thoracic segment, dorsal view x 2.0 (internal mould) from PL2203. 11, paratype NMV

P3047 12, cranidium, dorsal view x 1 .25 (latex cast) from PL2203. 12, paratype NMV P304864, pygidium, dorsal view x 1 .4 (internal mould) from

PL2203. 13, paratype NMV P304861, pygidium, dorsal view x 1.8 (latex cast) from PL2203. 14, paratype NMV P304860, pygidium,

ventral view (doublure) x 1.25 (internal mould) from PL2203. 15, paratype NMV P304863, pygidium, dorsal view x 1.5 (internal mould)

from PL2203. 16, paratype NMV P304865, pygidium, dorsal view x 1.7 (latex cast) from PL2203. 17a, holotype NMV P304717, pygidium,

lateral view x 1.1 (internal mould) from PL2203. 17b, same, dorsal view x 1.3. 17c, same, x 1.1 (latex cast). 18, paratype NMV P304862,

pygidium, lateral view x 1.5 (internal mould) from PL2203.

Andrew C. Sandford

Homalonotid trilobites from the Silurian and Lower Devonian

horizontal. In lateral view dorsal profile of axis inclined at about 30° to

the horizontal, postaxial ridge very steeply inclined.

Discussion. Digonus wenndorfi is abundant and dominates the

trilobite fauna at several localities. Except for a cephalon

(Holloway and Neil, 1982: figs 4A, 4B) the species is known

only from isolated tergites. Relative proportions of many

features (eg. glabellar and pygidial length/width ratios) are dif-

ficult to ascertain due to deformation. Nevertheless, two

distinct forms of wenndorfi can be recognised, elongate and

short morphs differing in the relative proportions of the

cephalon, glabella and pygidium. These morphs are not related

to size, nor are they products of deformation as their ranges in

size overlap, and they occur together on the same bedding plane

(Fig. 3). The differing morphological proportions within the

population are strongly bimodal rather than continuous.

Pygidial length-width ratios range between 0.76-0.93 (average

0.86) in the short morphs, in the long morphs between

1.11-1.12. Similarly, glabellar length-width ratios range

between 0.96-1.00 (average 0.99) in the short morphs, in the

long morphs between 1.15-1.23 (average 1.19). Similar

observations have been made for populations of D. gigas and

attributed to sexual dimorphism (Dahmer, 1914), although

Wenndorf (1990: table 31) demonstrated, with a much larger

sample size of 67 pygidia, that the variation in gigas is con-

tinuous rather than bimodal, with intermediate forms being the

most numerous, and so not reflecting sexual dimorphism.

Although the sample size for wenndorfi is much smaller (11

measurable specimens) the complete absence of intermediate

forms (e.g. pygidia with length-width ratios range between

0.93-1.1) is statistically significant. Whether the bimodality

reflects sexual dimorphism is uncertain, although the narrower

morphs strongly outnumber the wider morphs and so suggest

that it does not.

The subquadrate outline of the anterior part of the

cranidium, the weakly tapered trapezoid glabellar outline,

the wide pygidial axis, and the depth of the pygidial ring and

pleural furrows clearly indicate assignment to Digonus.

D. wenndorfi differs markedly from the D. gigas group and

more closely resembles the D. ornatus group in having a

relatively longer preglabellar field, wide fixigenae anteriorly,

and a transverse rather than weakly concave anterior cranidial

margin.

Digonus wenndorfi differs from most Pragian-Emsian

species of Digonus in lacking the elongate, straight-sided tri-

angular outline and a long produced tip characteristic of the

type and other taxa such as D. ornatus and D. intermedius. In

having shorter pygidial proportions, wenndorfi more closely

resembles other Lochkovian species, including D. laticaudatus

from North America, D. armoricanus from France, and D. roe-

meri from Europe. Compared to Pragian-Emsian species,

Lochkovian species of Digonus lack some of the features

characterising Digonus. These species can be interpreted as

reflecting ancestral morphologies, as might be expected in the

earliest representatives of a genus. ‘Trimerus- like’ features

including the raised postaxial ridge and weak glabellar lobation

of wenndorfi can be interpreted in this context.

Of Lochkovian species of Digonus, only D. zeehanensis

from Tasmania (redescribed below) is known sufficiently for

detailed comparison with D. wenndorfi. These taxa are very

close, but the latter differs in having slightly concave glabellar

sides, a longer glabella, more distinctly expressed glabellar

lobation, a shorter preglabellar field, a much shorter pygidium

with a relatively narrower pygidial axis, a more obtusely-

angled pygidial tip, and a lower postaxial ridge (Fig. 13).

With the exception of the latter, these features suggest that

zeehanensis represents a less derived morphology.

Digonus roemeri is a near-contemporary of D. wenndorfi,

recorded from the base of the Lochkovian ( [hesperius zone) in

Europe (Chlupac et al., 2000). The species is poorly docu-

mented and, as noted by Tomczykowa (1975), a number of taxa

have been assigned to it. Topotypes of D. roemeri (Morzadec,

1986: pi. 32 figs 1, 4, 6-10) share with wenndorfi short

pygidial proportions and the equally deep pygidial pleural and

ring furrows typical of Digonus. D. roemeri differs from

wenndorfi in that the pygidial axis is wider and the postaxial

ridge is not raised. In contrast to other species assigned to the

genus, pygidia of roemeri and the comparable D. laticaudatus

exhibit anteriorly continuous pygidial axial furrows,

interpreted here to reflect the ancestral morphology.

Many species assigned to Digonus are poorly documented

and comparison with D. wenndorfi is difficult. From Europe,

D. harpyius is known only from a rostral plate. The Emsian

D. goniopygaeus from England and D. crassicauda from

Germany are kn own only from pygidia. Despite the compar-

able short proportions, the pygidium of crassicauda differs

from that of wenndorfi in having a weakly defined postaxial

ridge and a narrow, recurved flange defining the pygidial tip

(Wenndorf, 1990: pi. 9 figs 1-3), as in other Emsian Digonus.

The Antarctic D. antarcticus differs markedly from wenndorfi

Figure 13. Digonus zeehanensis (Gill, 1949). la, NMV P304656, cephalon, dorsal view x 1.2 (internal mould) from PL1726. lb, same, enlarge-

ment of anterior margin x 2.5. 1c, same, lateral view of cephalon x 1.0. Id, same, dorsal view x 1.25 (latex cast). 2a, NMV P304657, cephalon,

dorsal view x 2.6 (internal mould) from “Little Henty River”. 2b, same, lateral view x 2.25. 3, NMV P304650, hypostome, ventral view x 2.2

(internal mould) from PL1726. 4a, NMV P304653, librigena, dorsolateral view x 1.3 (latex cast) from PL1726. 4b, same, lateral view. 5, NMV

P304652, thoracic segment, lateral view x 3.0 (latex cast) from PL1726. 6, NMV P14789, cranidium, dorsal view x 0.9 (latex cast) from PL1726.

7a, holotype NMV P14590, cranidium, dorsal view x 1.3 (latex cast) from PL1726. 7b, same, internal mould x 1.1. 8, NMV P304683, hypostome,

ventral view x 2.1 (latex cast) from PL1726. 9, NMV P304658, cranidium, dorsal view x 1.6 (latex cast) from PL6653. 10, NMV P304649,

pygidium, dorsal view x 1.1 (internal mould) from PL1726. 11, NMV P304655, cranidium, dorsal view x 1.0 (latex cast) from PL1726. 12, NMV

P7651, pygidium, dorsal view x 1.65 (internal mould) from “MtZeehan”. 13a, NMV P304648, pygidium, lateral view x 1.1 (internal mould) from

PL1726. 13b, same, dorsal view. 14, NMV P14787, pygidium, dorsal view x 0.75 (latex cast) from PL1726. 15a, paratype NMV P14592,

pygidium, lateral view x 1.0 (internal mould) from PL1726. 15b, same, dorsal view (latex cast). 15c, same, dorsoposterior view (internal mould).

15d, same, dorsal view. 16, NMV P304659, pygidium, dorsal view x 1.0 (latex cast) from “Mt Zeehan”.

Andrew C. Sandford

in having weakly expressed pygidial axial furrows, exception-

ally deep pleural furrows and a poorly expressed postaxial

ridge (Saul, 1965: pi. 17 figs 1-11).

Holloway and Neil (1982) considered specimens of Digonus

wenndorfi to be close to Trimerus lilydalensis Gill, 1949, also

from the Lochkovian of central Victoria. The availability of

many new specimens of wenndorfi and a revision of Gill’s

species does not support this comparison, with the latter

assigned to the new genus Wenndorfia.

Digonus zeehanensis (Gill, 1949)

Figure 13

Trimerus zeehanensis Gill, 1949: 70, pi. 9 figs 1, 2, 4, text-fig.

ID. — Tomczykowa, 1975: 11. — Wenndorf, 1990: 16. — Holloway and

Sandford, 1993: 93. — Schraut, 2000: 382.

Type material. Holotype NMV PI 4590 (cranidium, counterpart pre-

viously registered NMV P14591, Fig. 13.7) and paratype NMV

P14592 (pygidium, counterpart previously registered NMV P 1459 13)

from PL1726, Gill and Banks locality 16, Zeehan, Tasmania.

Registered material. 67 specimens: 2 cephala, 13 cranidia, 12 libri-

genae, 2 hypostomes, 11 thoracic segments, 27 pygidia. NMV P14787,

P14788 (counterparts), NMV P14789, NMV P14791, NMV

P304648-P304656, NMV P304662, NMV P304664-P304708 from

PL1726. NMV P304657 from “Little Henty River”, Zeehan. NMV

P304661 from “near Little Henty River”, Zeehan. NMV P304663 from

PL1725, Gill and Banks’ locality 15, Zeehan. NMV P304660, NMV

P304658 from PL6653, Zeehan. NMV P7561, NMV P304659 from

“Mt Zeehan”, Zeehan.

Stratigraphic distribution. Bell Shale, Boucotia australis

Assemblage Zone, mid-late Lochkovian.

Diagnosis. Cephalon trapezoid, sides straight, anterior margin

tricuspate, with short (0.05 times cephalic length) but wide

(length 0.25 times width) median cusp, lateral cusps about half?

the length of the median cusp. Glabella trapezoid, sides

weakly concave and converging at about 20°, length about 1.2

times width, anterior margin well defined, lobation weakly

defined. Axial furrows moderately impressed. Palpebral lobe

placed with midline opposite 0.52 glabellar length/0.42 crani-

dial length. Preglabellar field with length (sag.) 0.17 times

cranidial length. Anterior branches of facial suture straight and

converging at about 50°, curving abruptly to the exsagittal

anteriorly. Rostral suture transverse. Dorsal surface of rostral

plate triangular, short, length 0.15 times width. Hypostome

with middle furrow deep adaxially, shallow abaxially. Posterior

border of hypostome with long lateral lobes of length 0.17

times hypostomal length. Pygidium short, length 0.68 times

width, sides moderately convex and converging posteriorly at

about 110°. Pygidial axis 0.45 times pygidial width, 12 axial

rings, continuous with low postaxial ridge. Axial furrows taper-

ing at about 30°, moderately impressed posteriorly, not contin-

uous anteriorly opposite first ring. Pleural and ring furrows

deep. 8 ribs, rib-ring medially offset at fifth rib. Dorsal

exoskeleton with coarse pitting.

Discussion. The Bell Shale is strongly sheared, resulting in

wide variations in shapes and proportions of specimens.

Because Gill (1949) described the species from a limited

number of specimens, examination of a larger population

reveals a number of inaccuracies in his description. The

concavity of the preglabellar field and the upturning of the

anterior cranidial margin on the holotype (Fig. 13.7), consid-

ered diagnostic of the species by Gill, are features attributable

to tectonic distortion and are absent from other topotype cra-

nidia. Gill recorded lateral glabellar furrows as absent, but they

are weakly defined on most specimens. The pygidial axial fur-

rows are moderately impressed rather than poorly defined.

Despite the abundance of cephalic and pygidial tergites,

thoracic pleurae are unusually rare in the Bell Shale. From the

fragments available, there is no indication of spines on the

thorax as suggested by Gill.

Tomczykowa (1975) and Wenndorf (1990) assigned Gill’s

species to Trimerus, but the quadrate course of the anterior

branches of the facial and rostral sutures, the equally deep

pygidial ring and pleural furrows and the effacement of the

axial furrow anteriorly are more consistent with an assignment

to Digonus. Pygidia have a much wider axis (average width

0.46 pygidial width) than recorded by Gill, who cited the axial

width to be one third the pygidial width. However, as noted

above, the longer glabellar proportions, more distinctly

expressed glabellar lobation, shorter pygidial proportions with

a relatively narrower axis and a more obtusely-angled pygidial

tip suggest that D. zeehanensis represents a less derived

morphology compared to other Digonus. In these features,

zeehanensis is most closely comparable to D. roemeri from the

basal Lochkovian of France.

Environmental notes. Digonus zeehanensis dominates the tr-

ilobite fauna of the Bell Shale. At the best-sampled locality

(PL1726), the relative abundance of D. zeehanensis is >90%.

The fauna is typical of homalonotid-dominated assemblages,

being low diversity and otherwise comprising a proetid, a

cheirurid and a dalmanitid (Gill, 1950). The latter suggests

alignment with the deeper water Trimerus delphinocephalus-

Dalmanites limulurus Community of Mikulic, 1999. The pro-

portion of articulated specimens in populations of zeehanensis

is low. Of the 67 specimens, all are isolated tergites with

the exception of three cephala. Breakage is high in the sampled

populations (Br=27%). Specimens occur on bedding planes

in association with other fossil concentrations or in more

sparsely fossiliferous layers between the lag bands. The taphon-

omy is indicative of taphofacies Till and together with the

lithofacies and biofacies suggests a setting around maximum

storm wave base.

Dipleura Green, 1832

Type species: Dipleura dekayi Green, 1832. From the Middle

Devonian Hamilton Group, New York State, USA, by monotypy.

Other species included. Dipleura boliviensis Wolfart, 1968, D. gar-

ratti sp. nov., D. iberica Wenndorf, 1990, Homalonotus kayseri

Thomas, 1905, H. laevicauda Quenstedt, 1852, = H. simplex Richter

and Richter, 1926, D. lanvoiensis Morzadec, 1969, D. praecox

Tomczykowa, 1975, D. sp. (in Richter and Richter, 1943), D. sp. (in

Morzadec, 1981), D. sp. nov. (in Wenndorf, 1990).

Range. Upper Silurian (mid Ludlow)-Middle Devonian (Givetian).

Homalonotid trilobites from the Silurian and Lower Devonian

Revised diagnosis. Cephalon short, length 0.5 to 0.6 times

cephalic width, rounded triangular to semicircular in outline.

Glabella with sides straight or weakly concave, subparallel to

moderately convergent (20°), length 1.1 to 1.25 times width,

without lobation in maturity. Preglabellar field of moderate

length, 0.15-0.18 times cranidial length. Paraglabellar areas

indistinct. Palpebral lobes posteriorly placed, opposite 0.3 to

0.45 cranidial length. Eyes remote, 6-6 generally 1.7-1. 9 times

preoccipital glabellar width. Anterior branches of facial sutures

describing a broad curve and strongly convergent anteriorly,

between 80-100° opposite midlength of preglabellar field.

Rostral suture transverse to moderately convex forwards.

Ventral surface of rostral plate flat, without projection.

Pygidium with weakly defined trilobation, axial furrows very

shallow to effaced. Axis with ring furrows moderately

impressed to effaced, with weak to distinct posterior swelling,

without well defined postaxial ridge. Pleural furrows shallow to

effaced, invariably as shallow or shallower than ring furrows.

Finely papillate ornament.

Discussion. As with Digonus, Parahomalonotus and

Burmeisteria, the type species of Dipleura is one of the

youngest members of the genus and differs significantly from

older forms. General morphological changes in the genus over

time include a trend toward a less tapered glabellar shape with

increasingly concave sides, and a decrease in the definition of

pygidial segmentation and trilobation. In Middle Devonian

species a stronger cephalic convexity is developed, and the

contrast in depth between ring furrows and pleural furrows is

not as marked. The revised diagnosis differs from previous

ones in recognising the limited significance that pygidial out-

line holds as a generic character. In the case of Dipleura , the

oldest (early Ludlow) species, Dipleura garratti from Victoria,

has a long, acuminate triangular-shaped pygidium with an

acutely pointed tip, in contrast to the short parabolic outline and

rounded pygidial tip exhibited by Devonian taxa and consid-

ered characteristic of the genus. The upper Ludlow D. praecox

from Poland has an intermediate morphology, having a short

triangular outline with an angular tip.

Emphasis is placed on several characters listed by

Salter (1865), Reed (1918) and Sdzuy (1959) but omitted

by Tomcykowa (1975) and Wenndorf (1990). These include

the course of the facial and rostral sutures, eye position

and weak expression of paraglabellar areas. Several new diag-

nostic characters are added, including the absence of a

projection or keel on the ventral surface of the rostral plate, the

presence of a weak to distinct posterior swelling of the

pygidial axis and the absence of a well defined postaxial

ridge.

The revised concept of the genus excludes a number of

species that have been previously assigned to Dipleura (see

Wenndorf, 1990: table 1, Tomczykowa, 1975: table 3). These

include Burmeisteria ( Digonus ) accraensis from West Africa,

Homalonotus clarkei from Bolivia, Dipleura salteri Morris,

1988 from England and Trimerus (Dipleura) fornix Haas, 1968

from Turkey. Generic assignment of the two former species is

discussed under Digonus. D. salteri is tentatively assigned to

Trimerus ( Ramiotis ), discussed below. T. (D.) fornix is assigned

below to Wenndorfia, erected for many of the species previous-

ly assigned to Parahomalonotus. Cephalic outline, the stronger

segmentation of the pygidial axis compared to the pleural field,

and the definition of the pygidial axial furrow posteriorly were

considered by Wenndorf (1990) to be important generic char-

acters in distinguishing Dipleura from morphologically con-

vergent species of Parahomalonotus. In restricting

Parahomalonotus to a group close to the type species, the dis-

tinction between the two genera is marked. In particular, the

strong glabellar and pygidial axial convexity, strong glabellar

lobation and strong pygidial segmentation easily separate

members of Parahomalonotus s.s. from those of Dipleura. The

problem of convergence addressed by Wenndorf re-emerges

however, between Dipleura and species assigned below to

Wenndorfia. Dipleura and Wenndorfia share many characters

including a weakly tapering glabellar outline, effaced glabellar

lobation, a posterior eye position, a preglabellar field of mod-

erate length, an effaced pygidial postaxial ridge and pygidial

outlines that are for the most part rounded parabolic. For the

latter character triangular outlines are exceptional, expressed in

early representatives of each genus such as D. garratti and W.

lilydalensis (Gill, 1949). Many species assigned to Wenndorfia

can be immediately distinguished from Dipleura in having dis-

tinct pygidial segmentation, with pleural furrows being moder-

ately to deeply impressed. Such species include W. multicosta-

tus (Koch, 1883a), W. miloni (Renaud, 1942), W. elegans

(Tomcykowa, 1975), W. bostoviensis (Tomczykowa, 1975), W.

plana junior (Wenndorf, 1990) and W. sp. (=Digonus vialai in

Tomczykowa, 1975). However, in a number of taxa the pygidi-

al axial and pleural furrows are weakly impressed to indistinct,

including W. plana plana (Koch, 1883a), W. forbesi (Rouault,

1855) and W. fornix. Assignment of these convergent species to

Wenndorfia is indicated by consistent differences in the course

of the facial sutures between Dipleura and Wenndorfia. In

Dipleura , the facial sutures tend to be more strongly convergent

and the rostral suture more forwardly convex, giving a more

parabolic or V-shaped outline to the anterior margin of the

cranidium. By contrast, the rostral suture of Wenndorfia is

transverse or weakly convex forwards. The anterior branches of

the facial sutures tend to be less strongly convergent posterior-

ly, abruptly curved medially and more strongly convergent

anteriorly, giving the anterior margin of the cranidium a more

rounded, U-shaped outline.

Reed (1918) suggested that Dipleura was derived from

Digonus. More recent phylogenies are in accord in deriving

Dipleura directly from Trimerus, although there is disagree-

ment in the chronology of this transition. Sdzuy (1957: fig. 3)

considered Dipleura to have originated from Trimerus at the

Siluro-Devonian boundary. Tomczykowa (1975) established an

earlier origin for Dipleura, and suggested two species from the

upper Ludlow of Poland, Dipleura praecox Tomczykowa, 1975

and Trimerus permutus Tomczykowa, 1978 from the immedi-

ately underlying beds, to be closely related and to represent a

transitional li nk between the genera. An earlier origin for

Dipleura is indicated by its occurrence in lower Ludlow strata

of Victoria, supporting Wenndorf’s (1990: fig. 6) suggestion of

a Wenlock origin for the genus.

Dipleura is presumably derived from Lower Silurian

Andrew C. Sandford

Trimerus. Lower Silurian Trimerus are variably assigned in this

work to T. ( Trimerus ) or to T. ( Ramiotis ). T. ( Trimerus ) is

characterised by a suite of distinctive cephalic and pygidial

features, notably a glabellar outline markedly expanded across

LI -LI (tr.), raised glabellar profile, the strongly-defined

glabellar lobation, L1-L2 muscle scars, sagittal ridge, exsa-

gittal furrows and paraglabellar areas, the long and weakly con-

cave (tr.) preglabellar field, and the produced pygidial tip. In

the absence of most of these features species assigned to

T. ( Ramiotis ) more closely resemble Dipleura. Llandovery

species of T. ( Ramiotis ) exhibit features that show a strong

resemblance to those typical of Dipleura, sharing trapezoid

glabellar outlines, shorter preglabellar fields and marked

contrast between the depth of the ring furrows and pleural

furrows, with the latter very shallow to almost effaced.

Sdzuy (1957) interpreted Homalonotus ( Trimerus ) mongo-

licus Tchemycheva, 1937 from the Upper Silurian of Mongolia

as an intermediate form between Dipleura and Trimerus. Sdzuy

emphasised the posterior eye position, the rounded pygidial

outline and the marked contrast between the depth of the ring

furrows and almost effaced pleural furrows to support his inter-

pretation. The significance of these characters is overstated by

Sduzy. The markedly weak pleural furrows and rounded

pygidial outline of mongolicus emphasised by Sdzuy are not

features unique to Dipleura and occur amongst species of

T. ( Ramiotis ) and T. ( Edgillia ). The eyes of mongolicus are

clearly placed directly opposite the glabellar midlength

(Tchemycheva, 1937: pi. 1 fig. 8). The rounded pygidial outline

emphasised by Sdzuy is contradicted by Tchemycheva’ s

description of the pygidium as “triangular, usually elongated,

terminates in a thick spine ” (Tchemycheva, 1937: 25). In

strong contrast to Dipleura, the species exhibits a very long

preglabellar field (0.3 cranidial length) and the anterior branch-

es of the facial sutures are relatively weakly convergent (60°).

Tchemycheva’ s description of other features including a sub-

quadrate, weakly tapering glabellar outline, an evenly vaulted

glabellar profile, weak SI and indistinct S2 and S3, 13

pygidial axial rings, shallow pygidial pleural furrows, the

absence of a postaxial ridge ( “rhachis falling short of poster-

ior margin”) and the pygidial proportions (length 0.92 width)

indicate assignment to T. (Edgillia).

Dipleura garratti sp. nov.

Figure 14

Homalonotus sp. — Chapman, 1908: 220.

Type material. Holotype NMV P308644 (pygidium) from PL6615,

Eden Park, Victoria (Fig. 14.13). Paratypes NMV P308638, NMV

P308641 (cranidia), NMV P308639, NMV P308642, NMV P308645

(cephala), NMV P308643 (librigena), NMV P308637, NMV P308640,

NMV P308646 (pygidia) from PL6615. Paratypes NMV P308635-6

(cephalothoraxes) , NMV P308649, NMV P308651, NMV P308663,

(cephala), NMV P308657 (cranidium) from PL6614, Eden Park. NMV

P308648 from “Whittlesea”, Victoria. For localities see Fig. 11.

Registered material. 47 specimens: 4 cephalothoraxes, 8 cephala, 17

cranidia, 2 librigenae, 2 thoracic segments, 14 pygidia. NMV

P3045 1 3-P3 045 1 5 , NMV P304572, P304573, NMV

P308633-P308636, NMV P308649-P308657, NMV P308673 from

PL6614. NMV P308637-P308647, NMV P308659-P308672 from

PL6615. NMV P308658 from PL6625, Wandong, Victoria. NMV

P308648 from “Whittlesea”. Unregistered specimens from PL1793,

Clonbinane and Kenley locality 14c, Upper Plenty. For localities see

Fig. 11.

Stratigraphic distribution. As for Homalonotus williamsi.

Derivation of name. For Michael J. Garratt, for his contribution

to Victorian palaeontology and stratigraphy.

Diagnosis. Glabella trapezoid, length 1.05 times preoccipital

glabellar width, sides straight and converging at about 25°,

anterior margin well defined, very broadly rounded to trans-

verse. Length (sag.) of preglabellar field 0.15-0.18 times cran-

idial length. Palpebral lobe placed with midline opposite 0.47

times glabellar length/0.38 times cranidial length. Anterior

branches of facial suture angular, subparallel to axial furrows to

a point opposite 0.75 glabellar length, anteriorly converging at

about 80°. Rostral suture broadly curved. Ventral surface of

rostral plate with length about equal to width, flat, connective

sutures angular, anterior section converging at 40 degrees, pos-

terior section at 80°. Pygidium triangular, length equal to width,

sides straight and converging at 65°, tip acutely angular.

Pygidial axis with width 0.5 times pygidial width, 12 axial

rings, ring furrows moderately impressed, axis moderately

swollen posteriorly, continuous with wide but poorly defined

postaxial ridge. Axial furrows straight and tapering at about

33°, weakly impressed to indistinct. Pleural furrows weakly

impressed to indistinct. 6 pleural ribs, rib-ring medially offset

at second rib.

Description. Exoskeleton small (maximum length estimated 8 cm

from NMV P308644), occipital and pygidial convexity (tr.) moderate.

Dorsal exoskeleton finely granulose.

Cephalon with width about 1.6 times length, with semielliptic out-

line, sides moderately convex. Cranidial width about 1.64 times length.

Figure 14. Dipleura garratti sp. nov. 1, paratype NMV P308638, cranidium, dorsal view x 3.0 (internal mould) from PL6615. 2, paratype NMV

P308645, cephalon, dorsal view x 3.0 (latex cast) from PL6615. 3, paratype NMV P308646, pygidium, dorsal view x 3.8 (internal mould) from

PL6615. 4a, paratype NMV P308663, cephalon, ventral view (doublure) x 4.1 (latex cast) from PL6614. 4b, same, enlargement of rostral plate

x 15. 5, paratype NMV P308641, cranidium, dorsal view x 3.0 (internal mould) from PL6615. 6, paratype NMV P308642, cephalon, dorsal view

x 2.2 (internal mould) from PL6615. 7, paratype NMV P308643, librigena, ventral view (doublure) x 2.6 (latex mould) from PL6615. 8, paratype

NMV P308657, cranidium, dorsal view x 1.9 (internal mould) from PL6614. 9, paratype NMV P308649, cephalon, dorsal view x 2.0 (internal

mould) from PL6614. 10a, paratype NMV P308635, cephalothorax, dorsal view of cephalon x 2.2 (internal mould) from PL6614. 10b, same, dor-

sal view of thorax x 2.0. 11, paratype NMV P308639, cephalon, dorsal view x 1.8 (internal mould) from PL6615. 12, paratype NMV P308640,

pygidium, dorsal view x 3.5 (internal mould) from PL6615. 13a, holotype NMV P308644, pygidium, dorsal view x 2.1 (internal mould) from

PL6615. 13b, same, posterior view. 13c, same, lateral view x 2.8. 14, paratype NMV P308648, cephalon, oblique view x 3.0 (latex cast) from

PL6614. 15, paratype NMV P308637, pygidium, dorsal view x 3.5 (internal mould) from PL6615. 16, paratype NMV P308636, cephalothorax,

lateral view x 3.0 (internal mould) from PL6614. 17, paratype NMV P308651, cephalon, dorsal view x 3.3 (internal mould) from PL6614.

Homalonotid trilobites from the Silurian and Lower Devonian

Andrew C. Sandford

Glabellar length about 0.8 times cranidial length. Occipital ring 0.12

times glabellar length, slightly wider medially. Occipital furrow deeply

impressed, with weak forward flexure medially. Glabellar lobation

extremely weak to indistinct, best seen on NMV P308638 as very

shallow depression at adaxial end of SI placed opposite 0.3 times

glabellar length. Paraglabellar area very weakly defined. Length

(exsag.) of posterior border equal to occipital length adaxially, length-

ening slightly abaxially. Posterior border furrow transverse adaxially,

curving gently forwards abaxially, very wide, moderately impressed,

terminating distally. Postocular fixigenal area very short, length

(exsag.) 0.15 times cranidial length. Palpebral lobes placed remotely

(6-6 1.65 times preoccipital glabellar width). Palpebral lobe length

(exsag.) 0.15 times cranidial length, palpebral furrow indistinct.

Preocular fixigenal area of moderate width, 0.18 5-6, narrowing

slightly anteriorly, eye ridges very weakly defined. Librigena without

distinct border furrow or lateral border. Dorsal surface of rostral plate

very short (sag.), crescentic in outline. Ventral surface of rostral plate

kite-shaped, posterior width 0.2 times maximum width. Hypostomal

suture extremely weakly curved.

Thorax with thirteen segments. Axial furrows extremely shallow,

expressed as diagonally directed furrows on each segment, each

meeting posterior margin at axial articulating process on internal

mould. Pleural furrows wide and deep across axis, narrower (exsag.)

and deeper across pleural field.

Pygidial border furrow and border poorly defined. In posterior view

posterior margin of pygidium horizontal. In lateral view dorsal profile

evenly inclined, interrap ted by swelling of terminal piece.

Discussion. The assignment of this species to Dipleura is indi-

cated by the course of the facial sutures (anterior branches con-

verging at 90°), the posterior position of the eye and the almost

effaced pygidial axial furrows and pleural furrows. The short

preglabellar field and indistinct glabellar lobation are in accord

with this assignment. D. garratti is the earliest representative of

the genus. A number of differences with later Dipleura can be

interpreted as reflecting the closer affinities of garratti with

Trimerus, particularly its triangular pygidial outline and its pos-

teriorly raised axis that is continuous with a wide postaxial

ridge (Fig. 14.12).

In many features Dipleura garratti is most closely com-

parable to the German upper Pragian-lower Emsian

D. laevicauda, sharing a moderately tapered glabellar outline,

more elongate pygidial proportions and a relatively wide

pygidial axis. The course of the cephalic sutures is most like

that of the Bolivian Givetian D. boliviensis. Originally

described as a subspecies of D. dekayi, the relatively longer

cephalic proportions, more tapering glabella, more anteriorly

and less remotely placed eyes are significant in regarding

boliviensis as an independent species.

Environmental notes. Dipleura garratti occurs in a trilobite

fauna dominated by proetids and dalmanitids, with Homalon-

otus williamsi, aulacopleurids, odontopleurids and phacopids in

very low abundance. Although known from various localities

between Clonbinane and Eden Park, the fauna is well repre-

sented at two richly fossiliferous localities in the Macropleura

band at Eden Park, a horizon characterised by an abundance of

the large, thick-shelled brachiopod M. densilineata. At PL6615,

dalmanitids (relative abundance 50%) are more abundant than

proetids (relative abundance 21%), whereas at PL6614 the

proetids are dominant (relative abundance 55%) over dalman-

itids (relative abundance 26%). The relative abundances of

garratti and williamsi are similar at both localities (17-19% and

2% respectively).

The taphonomy and facies of Dipleura garratti differs

markedly between PL6614 and PL6615. At PL6615, 87% are

isolated tergites and the remainder are cephala. With the excep-

tion of the cephalon of Homalonotus williamsi all other

trilobites associated with garratti are represented by isolated

tergites, with the proportion of broken specimens 16%. The

lithology is best described as a bioclastic coquina in a siltstone

matrix. Assignment to shallow taphofacies TII is in accord with

Garratt’s (1983) assignment of the brachiopod fauna to the

shallow-water Notoconchidium Community (BA2). A moderate

energy environment at depths around normal wave base is

indicated. Slightly deeper conditions are indicated by the

taphonomy and lithofacies at PL6614, where 21% of specimens

of garratti are cephala and 21% are cephalothoraxes. The pro-

portion of broken specimens (9%) is lower than at PL6615. The

lithology at PL6614 is a poorly bedded micaceous siltstone,

and although bioclasts are extremely abundant they have not

been winnowed to form a coquina. The preservation suggests

an environment at depths below normal wave base.

Parahomalonotus Reed, 1918

Type species. Homalonotus gervillei De Verneuil, 1850. From the

Pragian of France, Turkey, Spain, Morocco, Romania and Turkey, by

original designation.

Other species included. Parahomalonotus diablintianus Morzadec,

1976, Homalonotus vialai Gosselet, 1912 (in Gosselet et al.), P. sp. A

(=P. gervillei in Haas, 1968), P. sp. B (=P. aff. gervillei in Wenndorf,

1990).

Other species tentatively included. Digonus sp. cf. E in Morzadec,

1986.

Range. Lower Devonian.

Revised diagnosis. Glabella moderately to strongly convex

(tr. sect.) and narrow, with length 1.2- 1.6 times width. Axial

furrows moderately to deeply impressed. Lobation distinct,

S1-S3 moderately to deeply impressed. Pygidial axis narrow

(0.35-0.4 times pygidial width anteriorly), weakly tapering

(-25-30°), with moderate to strong convexity independent of

the pleural convexity, raised posteriorly, continuous with wide

postaxial ridge reaching posterior margin, pygidial tip with

small point or short slender spine.

Discussion. The restricted diagnosis of Parahomalonotus

defines a tight group distinct from Wenndorfia, to which many

species previously assigned to Parahomalonotus have been

assigned. Species assigned to Parahomalonotus also share

weak glabellar tapering (0-18°), a preglabellar field of mod-

erate (0.2) to short (0.05) length, eyes placed posteriorly

(opposite 0.35-0.5 cranidial length), subparallel to moderately

convergent anterior branches of facial suture, a transverse

rostral suture, an obtusely angled (130-150°) to rounded

pygidial tip and equally well defined axial rings and pleural

ribs.

Pygidial morphology of Parahomalonotus is distinct from

that of Wenndorfia and is conservative, with the exception of

Homalonotid trilobites from the Silurian and Lower Devonian

P. diablintianus in which pygidial ring and pleural furrows are

relatively shallow and the pygidial outline distinctly rounded,

hi cephalic features, the younger late Pragian-Emsian forms

(P. sp. A, P. gervillei ) differ from earlier species in their

stronger glabellar convexity and lobation, and greatly reduced

preglabellar fields. Of the earlier taxa, P. vialai shows the

closest affinities with the type species and represents an inter-

mediate morphology in which glabellar furrows and lobation

are more moderately expressed.

To the species Parahomalonotus sp. A illustrated by Haas

(1968: pi. 30 figs 1-4 as P. gervillei ) from the Emsian of Turkey

can be added at least one of the cranidia (pi. 29 fig. 26)

described as Dipleura fornix, differing from other specimens of

fornix in having a transverse glabellar anterior margin and

straight rather than concave glabellar sides.

Trimerus Green, 1832

Type species. Trimerus delphinocephalus Green, 1832 from the

Wenlock Rochester Shale, New York State, by monotypy.

Subgenera included. Trimerus ( Trimerus ) Green, 1832, T. (Ramiotis)

subgen. nov., T. ( Edgillia ) subgen. nov.

Range. Llandovery-Lochkovian.

Revised diagnosis. Cephalon triangular to rounded pentagonal

in outline, length 0.6-0.7 times width, anterior margin entire,

trilobed or tricusped. Preglabellar field of moderate length to

very long, 0.16-0.35 times cranidial length, flat or weakly con-

cave (tr.) medially. Glabella generally with distinct lobation and

median indentation of anterior margin. Eyes placed forwardly,

with midline of palpebral lobes opposite 0.5-0.75 glabellar

length (0.38-0.5 cranidial length) and medially on genae (6-5

1.3- 1.7 times preoccipital glabellar width). Anterior branch of

facial suture more or less straight and moderately convergent

(45-60°) between eye and a point opposite midlength of

preglabellar field. Rostral suture on dorsal surface, transverse

or arching forwards evenly or with a median angle.

Paraglabellar areas large. Ventral surface of rostral plate flat or

weakly convex, without process. Thoracic axial furrows poorly

defined. Pygidium with axis of moderate width (0.3-0.6 times

pygidial width), not reaching posterior margin, axial furrows

moderately impressed, axial ring and pleural furrows distinct

but of variable depth, 6-12 rings, 5-10 ribs.

Discussion. The revised diagnosis incorporates and quantifies

most features listed in more recent diagnoses of Trimerus. New

characters include the relatively forward position of the eye, the

straight course of the anterior branch of the facial suture, and

the moderate axial width. Early diagnoses, such as Salter’s

(1865), predominantly list characters of a very general nature.

Three species groups are recognised in this work and

defined as the subgenera Trimerus (Trimerus), T. (Ramiotis)

and T. (Edgillia). Previous diagnoses of Trimerus emphasise

the well-defined glabellar lobation, triangular pygidial outline

and acuminate pygidial tip (i.e. a mucro) exhibited by the type

species and shared with closely related species including T. (T.)

cylindricus, T. (T.) vomer (Chapman, 1912) and T. (T.) johan-

nis. These features and a suite of other distinctive glabellar

features are considered here to be diagnostic only of the typical

subgenus T. (Trimerus). The forwardly arcuate course of the

rostral suture and the short length (sag.) of the dorsal section of

the rostral plate noted in previous diagnoses of Trimerus

(Tomczykowa, 1975, Thomas in Curtis and Lane, 1998) is

considered here to be only of specific significance for

T. (T.) delphinocephalus.

A second group comprising other Silurian species of

Trimerus can be recognised, and is described in this work as

T. (Ramiotis). Members of this group lack the produced pygidi-

al tip and distinctive glabellar features of T. (Trimerus). The

group is typified by a new upper Llandovery species from

Victoria, T. (R.) rickardsi. The species assigned to this group

share a suite of characters including less acute to obtusely

angled pygidial tips lacking a mucro, and an elongate,

weakly tapering, more or less straight-sided glabella with

weakly defined lobation. Tomczykowa (1975) included a slight

degree of tapering of the glabella in her diagnosis of Trimerus,

but this character is peculiar to T. (Ramiotis). The degree of

glabellar tapering in Trimerus varies between the strongly

tapered (-55°) and posteriorly expanded morphologies of

T. (Trimerus), moderately tapered trapezoid morphologies

of T. (Ramiotis), and very weakly tapered (<15°) subquadrate

morphologies of T. (Edgillia), the latter erected in this work

for a group of Upper Silurian-Lower Devonian species.

T. (Ramiotis) is further distinguished from T. (Trimerus) by a

tendency towards a shorter preglabellar field, shorter pygidial

proportions and more weakly defined pygidial segmentation.

Trimerus (Edgillia) can be distinguished from the Silurian sub-

genera by a distinctive morphology typified by the Victorian

T. (E.) kinglakensis (Gill, 1949). The species assigned share a

very weakly tapered, subquadrate glabellar outline, weakly

defined glabellar lobation, and lack the raised postaxial ridge

present on most Silurian representatives of Trimerus.

Sdzuy (1959) considered Trimerus to comprise also the sub-

genus Dipleura. The revised diagnosis of Dipleura is in accord

with Tomczykowa (1975) and Wenndorf (1990) in recognising

Dipleura and Trimerus as independent genera. Sdzuy’s diag-

nosis of T. (Trimerus) emphasises differences from Dipleura,

listing the longer cephalic proportions, a more tapering gla-

bella, distinct glabellar lobation and paraglabellar areas, a for-

wardly convex rostral suture, an acuminate pygidial tip, and

more distinct pygidial segmentation. Diagnoses of Trimerus by

Thomas (in Curtis and Lane, 1998) and Tomczykowa (1975)

closely follow Sdzuy’s brief subgeneric diagnosis, but incor-

porate only some of the features listed by him. Importantly,

both Thomas and Tomczykowa omitted the morphology of the

rostral plate as a diagnostic character. Holloway and Neil

(1982) suggested the significance of homalonotid coaptative

morphologies, and in accord with this view the absence of a

rostral process is reinstated in the diagnosis. In emphasising

this feature and in the presence of other differences, a number

of Lower Devonian species previously assigned to Trimerus are

excluded, including Homalonotus noticus from South America

and South Africa), Burmeisteria (Digonus) accraensis from

Ghana and Trimerus novus Tomczykowa, 1975 from Poland.

Edgecombe and Fortey (2000) reassigned Homalonotus

linares Salter, 1861 from the Pffdolf of Bolivia to Trimerus.

The species exhibits a number of features that are not com-

Andrew C. Sandford

patible with this assignment. The axial ring count (14-16) is

higher than any species assigned to Trimerus (ranging 6-12),

the width of the axis (up to 0.7 width) is greater than in any

species assigned to Trimerus (ranging 0.3-0.6 width), the

pygidium is longer (length/width ratio 1 . 1-1 .2) than all species

of Trimerus (length/width ranging 0. 6-1.0) except for

T. ( Trimerus ) cylindricus Salter (1865), and the cephalic pro-

portions are longer (“ transverse width slightly exceeding

length Edgecombe and Fortey, 2000: 332) than any species of

Trimerus (length/width ranging 0.6-0.7), complementing its

elongate pygidial proportions. These features are more com-

patible with assignment to Burmeisteria. The type species,

B. herschelii exhibits comparably high pygidial segmentation

(16-17 axial rings, 9-11 pleural ribs), elongate pygidial pro-

portions and a wide pygidial axis. Although the course of the

rostral suture and the morphology of the rostral plate (including

the presence of a ventral process) for B. linares remains uncer-

tain, there is a suggestion of moderate convexity of the rostral

plate in one of the cranidia illustrated by Edgecombe and

Fortey (2000: pi. 2 fig. 16).

In addition to the several species reassigned to Burmeisteria

and Dig onus (discussed above), a considerable number of

species assigned to Trimerus by Tomczykowa (1975) and

Wenndorf (1990) are assigned to other genera. T. lilydalensis is

assigned below to Wenndorfia. Pygidia from the upper Pragian

of Morocco, identified by Schraut (2000) as T. sp. cf. crassi-

cauda are too fragmentary for confident assignment to

Trimerus , although the shallower axial ring and pleural furrows

preclude assignment to the German species. The relationships

of a number of poorly documented taxa previously assigned to

Trimerus are uncertain, including Homalonotus acuminatus

Tromelin and Lebesconte, 1876 and the French H. leheri

Barrois, 1886.

Trimerus ( Trimerus ) Green, 1832

Type species. Trimerus delphinocephalus Green, 1832, from the

Wenlock Rochester Shale, New York State, by monotypy.

Other species included. Homalonotus ( Trimerus ) cylindricus Salter,

1865, T. (T.) flexuosus Benedetto and Martel (in Baldis et al., 1976),

H. harrisoni McCoy, 1876, H. (T.) johannis Salter, 1865, H. vomer

Chapman, 1912, T. (T.) sp. A in Alberti (1970), T. sp. in Owens (1994).

Range. Wenlock-Ludlow, Pfldoli?

Diagnosis. Glabella moderately to strongly expanded across

LI -LI (tr.), strongly raised, markedly narrower (tr.) anteriorly

than posteriorly (sides tapering at 33-55°, width opposite S3

less than 0.65 times LI -LI). SI moderately to strongly

expressed, S2 and S3 distinct or fused with SI to form a shal-

low exsagittal depression. LI and L2 with low ovoid swellings.

Sagittal ridge of glabella well defined. Preglabellar field long to

very long (0.22-0.35 times cranidial length), distinctly concave

(tr. sect.). Pygidial length equal to or greater than width.

Pygidial ring furrows and pleural furrows of similar depth,

10-12 axial rings, 7-9 ribs. Pygidium with acutely produced tip

or with short, spine-like process.

Discussion. The type species Trimerus delphinocephalus

belongs to a distinct species group within Trimerus, restricted

in distribution to the mid Wenlock-lower Ludlow interval. The

group is easily recognised in having distinctive glabellar

features, particularly the glabella with an outline markedly

expanded across Ll-Ll (tr.), raised profile, distinct lobation,

swellings on LI and L2, and the sagittal ridge. In comparison

to other members of Trimerus, these species also have more

elongate preglabellar fields, more elongate and more highly

segmented pygidia, and bear a short spine or acute process on

the pygidial terminus. The species assigned are easily distin-

guished from other Trimerus, in which the characters listed are

only occasionally or weakly expressed.

The characteristic cephalic features of Trimerus ( Trimerus )

are expressed most strongly in T. (T.) johannis from the upper

Wenlock of England and T. (T.) vomer from the basal

Ludlow in Victoria. These species are interpreted as the most

highly derived of those assigned. Populations of T. (T.)

delphinocephalus show wide morphological variability and the

cephalic features characteristic of the subgenus are variably

expressed, although they are clearly present in specimens fig-

ured by Whittington (1993: figs 1, 2). Pygidia of delphino-

cephalus differ from those of johannis and vomer in having

shallower ring furrows and pleural furrows, and a short spine-

like process posteriorly. In outline, the depth of the pygidial

furrowing and presence of a posterior spine a single pygidium

documented from the Upper Silurian of Morocco (Alberti,

1970, Schraut, 2000) closely resembles pygidia of

delphinocephalus and is also assigned to the subgenus.

Trimerus ( Trimerus ) flexuosus from the Wenlock-Ludlow?

of Argentina is poorly known but is clearly attributable to

T. (Trimerus). Benedetto and Martel (in Baldis et al., 1976)

describe the species as having a raised glabella with distinct

SI -S3, subcircular-ovate swellings on LI, and strongly defined

paraglabellar areas, features characteristic of the subgenus. The

pygidium closely resembles that of T. (T.) sp. (in Alberti, 1970)

from Morocco in outline, in the depth of the pygidial furrowing

and in the presence of a posterior spine. The rostral suture is

convex, as in the type species.

An incomplete cranidium figured as Trimerus sp. from the

upper Wenlock Brinkmarsh Beds of England (Owens, 1994: pi.

2 fig. J) can be assigned to T. (Trimerus). In outline and

height the glabella is not unlike that of T. (T.) johannis from the

nearby area, to which it may belong.

The anterior margin of the cephalon is variably expressed in

Trimerus (Trimerus). In T. (T.) vomer, the angle of convergence

of the sides of the cephalon increases abruptly opposite the

antero-lateral comers of the cranidium, giving the cephalon an

irregular pentagonal outline. In T. (T.) johannis (and possibly

T. (T.) flexuosus) the anterior margin of the cephalon is tri-

cuspate, with the sides of the cephalon invaginated opposite the

connective suture. The weakly trilobate anterior margin of the

cephalon of T. (T.) delphinocephalus is intermediate between

these morphologies.

Trimerus (Trimerus) harrisoni (McCoy, 1876)

Figures 5B, 19.7, 19.9, 19.11

Homalonotus harrisoni McCoy, 1876: 19, pi. 23 fig. 11.

Trimerus harrisoni. — Gill, 1949: 65, text-fig. 1A. — Sandford, 2000:

189, figs. 17A-E.

Homalonotid trilobites from the Silurian and Lower Devonian

Remarks. I recently provided a comprehensive synonymy,

revised diagnosis and description for Trimerus ( Trimerus )

harrisoni (see Sandford, 2000). No new material has been

obtained. Poor preservation of all known cranidia obscures

many features of the cephalon pertinent to its subgeneric

assignment. The glabella is not strongly raised, although this

is true also of the type species Trimerus {Trimerus) del-

phinocephalus. The glabella tapers very strongly forwards,

although whether bell shaped or trapezoid in outline is not clear

as the best-preserved specimen is somewhat crushed. The poor-

ly known pygidia of harrisoni resemble those of the type

species in the depth and relative depth of the pleural and ring

furrows, although differ in having a prominent postaxial ridge

and possibly in lacking a posterior spine. In respect to these

latter differences, the pygidial morphology of harrisoni is not

incompatible with T. ( Ramiotis ). However, the strong tapering

of the glabella and exceptional length of the preglabellar field

are emphasised here in assigning the species to T. {Trimerus).

Trimerus {Trimerus) vomer (Chapman, 1912)

Figure 15

Homalonotus vomer Chapman, 1912: 298, pi. 62 figs 2, 3, pi. 63 fig.

2, non pi. 63 fig. 1 (= Trimerus {Ramiotis) otisi sp. nov.)

Homalonotus {Trimerus) vomer . — Reed, 1918: 323.

Trimerus vomer . — Gill, 1949: 65, text-fig. 1C non IB {=Trimerus

{Ramiotis) otisi sp. nov.). — Tomczykowa, 1975: 11. — Wenndorf,

1990: 16.— Schraut, 2000: 383.

Type material. Holotype NMV PI 2301 (cephalon and displaced thorax,

figured Chapman, 1912, pi. 62 fig. 1, 2, Gill, 1949a, text-fig. 1C, Fig.

15.4 herein) from “Wandong”, Victoria. Paratype NMV P12302

(thoracopygon, figured Chapman, 1912, pi. 63 fig. 2 from “Wandong”.

Paratype NMV P12303 (cephalon, figured Chapman, 1912, pi. 63

fig. 1, Gill, 1949a, text-fig. IB) from “Wandong”. For localities see

Fig. 11.

Registered material. 55 specimens. NMV P455, NMV P529, NMV

P16415, NMV P136623-P136627, NMV P136629-P136633, NMV

P137158, NMV P137291, NMV P137910 from “Wandong”. NMV

P 1 366 1 2-P 1 36622 , NMV P136628, NMV P136680, NMV P137120,

P137121, NMV P137126-P137137 from PL286, Williams locality

F22, Kilmore East, Victoria. NMV P136634-P 136636 from “Kilmore

East-Sunday Creek Road”, Kilmore East. NMV P136637 from

“Langford Park”, Kilmore East. NMV PI 36846, NMV PI 37887 from

“Kilmore”, Victoria. NMV P137122-P137124, NMV P137144, NMV

PI 38649 from “Kilmore- Wandong”. NMV P137144 from PL868,

Kilmore East. Yan Yean Formation. NMV P136638 from “Heathcote”,

Victoria. For localities see Fig. 11.

Revised diagnosis. Cranidial width 1.5 times length. Glabella

strongly raised, length equal to width, strongly bell shaped in

outline, much narrower anteriorly than posteriorly, anterior

margin well defined, with deep medial indentation. SI -S3 dis-

tinct, SI with deeply impressed apodeme at adaxial end.

Paraglabellar area very strongly defined. Preglabellar field very

long, 0.3 times cranidial length, weakly concave (tr. sect.).

Palpebral lobes placed opposite 0.5 cranidial length (0.7 glabel-

lar length). Weak but distinct eye ridges. Anterior branches of

the facial suture straight, converging at about 55° to a point

opposite midlength of preglabellar field. Rostral suture trans-

verse. Dorsal section of rostral plate triangular, long, 0.1

cephalic length. Ventral section of rostral plate elongate, width

0.85 times length, connective sutures straight and converging

posteriorly at 35°. Pygidium triangular, length equalling width,

with broad based, acutely pointed tip. Axial furrows moderate-

ly to deeply impressed. Axial width (measured across second

ring) 0.37 times pygidial width. Axis raised, markedly swollen

posteriorly. Wide postaxial ridge. 10-12 axial rings. 8 pleural

ribs with nineth rib reduced or absent. Pygidial pleural and ring

furrows deep, of equal depth. Rib-ring medial offset at fifth rib.

Description. Exoskeleton maximum length estimated 12 cm long.

Exoskeleton granulate, more densely in the alae, finely tuberculate tho-

racic segments.

Cephalon triangular, length 0.8 width, in transverse and sagittal sec-

tion posteriorly convex, anteriorly concave, lateral margins converging

at 70-80°, genal angles and anterior tip rounded. Glabella 0.6 cephalic

length, strongly bell shaped, narrowing markedly opposite palpebral

area, posterior width equal to length and twice anterior width, in

section (tr., sag.) weakly convex posteriorly, less so anteriorly.

Occipital ring transverse, lower than glabella, 0.1 glabellar length,

slightly wider at medial apex, in transverse section arched at medial

apex, sloping at a uniform gradient abaxially, not interrupted by axial

furrow and thus continuous with posterior border. Occipital furrow

deeply impressed, strongly deflected forwards medially and less so

abaxially, wider at medial apex. SI a wide shallow furrow directed

inwards backwards between 0.2 and 0.4 preoccipital glabellar width,

deeper at extremities. LI weakly defined as an independently convex,

triangular lobe, widest abaxially, maximum exsagittal length 0.3

glabellar length. S2 and S3 weakly defined as wide shallow depres-

sions not connected with axial furrows. L2 and L3 undefined. Frontal

lobe impressed medially by a short (sag.) wide notch. Axial furrow

developed posteriorly as large semicircular alae as long as and placed

opposite LI. Anteriorly axial furrow very wide, deepening opposite

antero-lateral comer of glabella. Preglabellar furrow indistinct, defined

as a change in height from the frontal lobe to the frontal area. Frontal

area long (sag.), 0.4 glabellar length. Medial area increasingly concave

anteriorly, margins increasingly convex posteriorly in transverse

section. Genae inflated. Fixigenae wide (tr.), approximately 0.5 pre-

occipital glabellar width at midline. Palpebral area wide and convex

(tr.), palpebral lobe inclined at 45°, semicircular, 0.25 glabellar length

(sag.), placed anterior of and adjacent to glabellar transverse midline,

weak eye-ridge directed inwards forwards to a point opposite S3.

Anterior to palpebral area fixigenae sloping down to frontal area, not

extending anteriorly as far as glabella. Posterior to palpebral lobe

fixigenae wide (exsag.), 0.33 glabellar length, narrowing abaxially,

strongly convex. Posterior border furrow wide, shallowing and curving

forwards abaxially. Posterior border lower than genal area, increasing-

ly convex (exsag.) and widening to twice occipital ring width (sag.)

abaxially. Genal angle broadly rounded. Anterior facial suture con-

verging forwards at about 60°, meeting connective suture very close to

margin at a point opposite 2/3 sagittal length of frontal area (measured

from glabella). Connective sutures short on dorsal surface, diverging

forwards at 90°. Rostral suture transverse. Posterior branch of facial

suture transverse adaxially, curving backwards abaxially, crossing

margin just anterior of genal angle. Librigenae triangular, convex,

steep. Eye small, raised above genal surface. Lateral border furrow

defined as an angular change in slope, less distinct toward genal angle.

Lateral border narrowing anteriorly by a factor of four from genal

angle, flat and horizontal. Lateral border and furrow indistinct anterior

to genae. Anterior facial sutures converging at 60°, close to margin and

curving inwards anteriorly, meeting connective suture on a transverse

line 0.3 sagittal length of frontal area from anterior tip. Connective

suture short on dorsal surface, diverging at 90°. Ventral portion of

Andrew C. Sandford

Homalonotid trilobites from the Silurian and Lower Devonian

rostral plate flat, elongate pentangular, long (sag.), 0.4 cranidial length

(extending to anterior margin of glabella), maximum width 0.8 length,

placed at 0.75 rostral length. Connective sutures straight, converging

posteriorly at 35°, posterior margin transverse, 0.4 maximum width.

Dorsal portion of rostral plate triangular to weakly crescentic, flat, very

short (sag.) length 0.2 width between posterolateral corners and 0.2

ventral length. Anterior margin straight abaxially, each side converging

at 110°, medially rounded. Rostral suture convergent at 170° laterally

(to one third maximum width), transverse medially. Connective sutures

short (exsag.) apparently marginal between posterolateral comers of

dorsal portion and anterolateral corners of ventral portion. Doublure

posterior margin transverse, as wide as rostral plate adjacent to

connective suture but narrowing adaxially. Adjacent to lateral margin

doublure concave in section such that it closely parallels the dorsal

exoskeleton.

Thorax 1 1 segments. Axis cigar shaped, weakly convex (tr.), wide,

0.7 (max.) thoracic width in dorsal view. Pleural field narrow in dorsal

view, 0.15 thoracic width, convex (tr.), flexed to subvertical, twice as

long abaxial of flexure than adaxial. Axial rings convex (sag.), trans-

verse, wider medially than abaxially. Pleural furrow continues onto

rings, deep slot-like, defining anterior band wider abaxially. Axis dis-

tinguished from pleural field by independent convexity and by a

depressed area in the posterior edge of the pleurae. Pleural furrow

divides narrow anterior band from posterior band twice as wide,

shallows towards tip. Abaxially of flexure pleurae widen slightly,

almost wholly occupied by articulating facet, which has a rounded tip.

Pygidial proportions as for cephalon. Trilobation distinct. Anteriorly

axis as wide as pleurae, tapering uniformly, 0.8 pygidial length, in

transverse section axis weakly convex anteriorly to strongly convex

posteriorly. In sagittal section axis concave anteriorly, posteriorly with

long prominent swelling and strongly concave. 9-10 distinct rings,

swelling 0.25 axial length and very feintly ringed. Axial rings very

weakly convex (sag.) and weakly convex-forwards. Anterior ring

furrow higher than others, second ring with pseudo-articulating half-

ring. Rings 1-7 of u ni form width, posterior rings (8+) as narrow ridges

Posterior of axis border strongly arched (tr. sect.) and high. Axial

furrow shallow and wide. Pleural field uniformly convex. Pleural fur-

rows distinct. 9 ribs, wider than rings, and widening abaxially, flat

(exsag.). Interpleural furrows not distinct. Border narrow, concave,

widening posteriorly.

Remarks. Many of the characters listed as diagnostic of

Trimerus ( Trimerus ) are strongly expressed in T. (T.) vomer,

including the definition of SI and LI and L2 swellings, the

paraglabellar area, the length of the preglabellar field and the

bell-shape of the glabella. T. ( T .) vomer also displays a number

of unusual characters including distinct eye ridges and deep S 1

apodemes, and further differs from other members of Trimerus

{Trimerus) in having a particularly long rostral plate (dorsally),

and very forwardly placed eyes. The deep SI apodemes are one

of the most distinctive features of vomer. The orientation and

position of these apodemes appears to be somewhat variable,

however, being transverse on some specimens, diagonal on

others, and sagittal on others. These differences may well be

attributable to deformation, as is suggested by the correlation of

glabellar proportions with apodeme orientation. Specimens

with tectonically shortened glabellae (L:W~0.8) have trans-

verse apodemes, those with tectonically elongated glabellae

(L:W~1.1) have sagittally directed apodemes. The prede-

formational orientation was probably diagonal, as in the

holotype.

Although with many unique characters, Trimerus ( Trimerus )

vomer is most closely comparable to T. (T.) johannis from the

Wenlock of Wales. These species share a transverse rostral

suture, a markedly raised and very strongly expanded (tr.)

glabella (more exaggerated in vomer), very distinct and large

paraglabellar areas and a distinctly concave preglabellar field.

The deep ring furrows and pleural furrows, the strong swellings

on the pygidial axis posteriorly (more prominent on vomer) and

the acute process defining the pygidial tip distinguish vomer

and johannis from other species of T. {Trimerus). These two

species differ in that vomer has more forwardly placed

eyes, distinct eye ridges, a longer preglabellar field, an entire

cephalic anterior margin, deep apodemes on SI and distinct

S2-S3 (fused to define a shallow exsagittal furrow in johannis).

As noted by Chapman (1912), Trimerus {Trimerus) vomer is

also close to the type species, T. {T.) delphinocephalus. Feint

eye ridges and very weak LI apodemes have been observed

(Whittington, 1993, fig. 2a) on delphinocephalus, and are

comparable to those on vomer (Figs 15.3-15.4) The most con-

spicuous differences include the much wider pygidial axis,

shallower pygidial furrows, the convex rostral suture, the

angular (rather than straight) connective sutures, the low

glabella and and the less elongate pygidial outline of

delphinocephalus.

The cephalon designated as paratype by Chapman and con-

sidered by him to be a juvenile form is not conspecific with the

holotype. The specimen (NMV P12303, see Fig. 20.1) lacks the

bell shaped glabellar outline and deep lateral glabellar furrows

of Trimerus {Trimerus) vomer, further differing from it in hav-

ing distinct subocular and sutural furrows. The specimen is

assigned in this work to T. {Ramiotis) otisi. Aspects of Gill’s

Figure 15. Trimerus {Trimerus) vomer (Chapman, 1912). la, NMV P136613, cephalon, dorsal view x 1.2 (latex cast) from PL286. lb, same, ven-

tral view (doublure) x 2.45. 2, NMV P136619, cranidium, dorsal view x 1.0 (internal mould) from PL286. 3a, NMV P136622, cephalon, dorsal

view x 1.15 (internal mould) from PL286. 3b, same, oblique view x 1.35. 3c, same, lateral view x 1.35. 4a, holotype NMV P12301, cephalon and

displaced, incomplete and partly enrolled thorax, anterior view of cephalon x 0.95 (internal mould) from “Wandong”. 4b, same, dorsal view of

cephalon and thorax x 0.88. 5, NMV P138649, cranidium, dorsal view x 0.92 (internal mould) from “Kilmore- Wandong”. 6, NMV P136638,

cephalon, dorsal view x 0.85 (internal mould) from “Heathcote”. 7, NMV P16415, cephalon and incomplete thorax, dorsal view x 1.0 (internal

mould) from “Wandong”. 8, paratype NMV P12302, thoracopygon, dorsal view x 0.92 (internal mould) from “Wandong”. 9a, NMV P136625,

pygidium, dorsal view x 0.85 (internal mould) from “Wandong”. 9b, same, lateral view x 1.05. 9c, same, posterior view x 0.85. 10, NMV

P137291, pygidium, dorsal view x 1.1 (internal mould) from “Wandong”. 11, NMV P137158, pygidium, dorsal view x 1.5 (internal mould) from

“Wandong”. 12, NMV P137124, pygidium, dorsal view x 1.3 (internal mould) from “Kilmore- Wandong”. 13a, NMV P455, thoracopygon,

Odorsal view x 1.1 (internal mould) from “Wandong”. 13b, same, lateral view x 1.2. 14, NMV P136637, pygidium, dorsal view x 1.05 (internal

mould) from “Langford Park homestead, Kilmore East”. 15, NMV P136633, pygidium, dorsal view x 1.25 (internal mould) from “Wandong”. 16,

NMV PI 379 10, pygidium, dorsal view x 1.0 (internal mould) from “Wandong”.

Andrew C. Sandford

(1949) redescription of vomer are clearly based on this

paratype, notably the description of the axial and glabellar

furrows as shallow and faint (respectively).

Documenting an increasingly distal eye position in a suc-

cession of Victorian homalonotids, Gill suggested a migration

of the Trimerus eye through time. In addition to the problem

that that the width of the librigenae and eye position for

T. ( Trimerus ) vomer is measured from the paratype cephalon of

T. (. Ramiotis ) otisi, Gill’s model is flawed firstly, in that only

two of the species in Gill’s model can be assigned to Trimerus,

secondly, in that the relative stratigraphic positions of the

species in Gill’s model are incorrect.

Environmental notes. Although no complete exoskeletons are

known from the population of Trimerus ( Trimerus ) vomer, the

articulation ratio of the population as a whole is high

(Ar=28%). T. (T.) vomer occurs in a fine siltstone lithology at

all of the few localities from which it is known. The holotype is

a cephalon displaced from an articulated thorax (Fig. 15.4),

interpreted as a moult assemblage. As for T. ( Edgillia ) king-

lakensis, articulated thoracopygons, cephalothoraxes and partly

disarticulated thoraxes are interpreted as exuvial configurations

(taphofacies TIV). An outer shelf deep-water habitat below

maximum storm wave base is suggested for vomer.

Trimerus ( Edgillia ) subgen. nov.

Type species. Trimerus kinglakensis Gill, 1949 from the Lochkovian

Hume vale Siltstone, central Victoria.

Other species included. Trimerus ( Trimerus ) grandis Benedetto and

Martel (in Baldis et al., 1976), T. ( Edgillia ) jelli sp. nov., Homalonotus

(Trimerus) mongolicus Tchemycheva, 1937, H. vanuxemi Hall, 1859.

Other species tentatively included. Homalonotus major Whitfield,

1881.

Range. Upper Silurian-Lower Devonian.

Derivation of name. For the late E. D. Gill, for his contribution

to Victorian palaeontology.

Diagnosis. Glabella subquadrate, length about 1.0 times width,

sides straight and weakly tapered (converging at around

15-20°), anterior margin transverse, well defined. S2 and S3

indistinct, SI indistinct or weakly defined, not extending to

axial furrows. Eye placed more or less opposite glabellar

midlength. Hypostomal middle furrow with deep impressions

abaxially. 10-14 pygidial axial rings. Pygidial postaxial ridge

poorly defined. Ring furrows deep, pleural furrows shallow.

Pygidial length 0.85-1.0 times width.

Discussion. Represented by a population sample of over 300

partly articulated exoskeletons, Trimerus (Edgillia) king-

lakensis is undoubtedly the best represented species of

Trimerus from the Prfdolf-Lower Devonian interval. T. (E.)

kinglakensis differs markedly from many earlier represen-

tatives of Trimerus in its glabellar morphology, principally in

having a subquadrate outline and a raised but evenly-vaulted

surface. Species assigned here to T. (Ramiotis) differs in having

a more strongly tapered and generally more elongate glabellar

outline, with many exhibiting weak glabellar lobation and

rounded anterior glabellar margins and pygidia with raised

postaxial ridges. The glabellar outline strongly expanded across

Ll-Ll (tr.), distinct glabellar lobation, paraglabellar areas, and

the presence of a glabellar longitudinal ridge and glabellar

antero-median indentation in T. (Trimerus) distinguishes

kinglakensis from that group. The morphology exhibited by

kinglakensis is shared with several poorly known Upper

Silurian-Lower Devonian taxa and defines a species group for

which T. (Edgillia) is established.

Homalonotus vanuxemi from North America is roughly con-

temporary with Trimerus (Edgillia) kinglakensis, occurring in

Lower Devonian strata of New York State. The species was

originally described from its thorax and pygidium (Hall, 1859).

The later documentation of the cranidium (Hall and Clarke,

1888: p. 11, plate 5b, Williams and Breger, 1916: plate 22, figs

12, 21, Shimer and Shrock, 1944: plate 272, fig. 32) demon-

strates a cephalic morphology closely comparable with king-

lakensis. In particular, the straight sides, transverse anterior

margin and weakly tapered outline and proportions of the

glabella of vanuxemi are almost identical to the Victorian

species. With respect to the morphology of the preglabellar

field, the illustrations of the cranidium by Hall and Clarke and

Shimer and Shrock are not in close agreement. Hall and Clarke

noted an exceptionally long preglabellar field and a transverse

rostral suture, although their observations were based on a

single fragment. Shimer and Shrock illustrated a complete

cranidium with a somewhat shorter preglabellar field, and

although the rostral suture is not clearly depicted it appears

forwardly convex in outline. In these respects the cephalon

illustrated by Shimer and Shrock is very close to kinglakensis

and supports assignment of vanuxemi to T. (Edgillia). The

pygidia of these two species also share a relatively high degree

of segmentation and both lack a raised postaxial ridge. The rel-

ative depth of the pygidial pleural furrows of vanuxemi is diffi-

cult to ascertain from the illustrations available. However, Hall

and Clarke’s illustration of a large specimen in lateral view

(Hall and Clarke: pi. 5b fig. 2) suggests shallower pleural

furrows than the ring furrows, as in kinglakensis.

Trimerus (Trimerus) grandis from the Upper Silurian-Lower

Devonian of Argentina was described by Benedetto and Martel

in Baldis et al. (1976) from a single specimen. Assignment of

this species to T. (Edgillia) is supported by the raised, evenly

vaulted glabellar profile, the subquadrate glabellar outline, the

poorly defined glabellar lobation, and the relative shallowness

of the pygidial pleural furrows relative to the ring furrows. The

higher degree of pygidial segmentation (11-12 axial rings) is in

accord with assignment to T. (Edgillia).

A new species represented almost entirely by fragmented

tergites from the Lochkovian of Victoria can also be assigned to

Trimerus (Edgillia). The material available is closely compar-

able to T. (E.) kinglakensis and T. (E.) vanuxemi and is

described in this work as T. (E.) jelli. There are few other

homalonotids recorded from the Lower Devonian that can be

confidently assigned to T. (Edgillia). Homalonotus major was

described from a single, incomplete but very large thoracopy-

gon. Whitfield (1881) estimated the specimen to represent an

individual 15.5 inches (31 cm) and in its very large size

the species is comparable to kinglakensis, vanuxemi and T. (E.)

grandis. The depth of the axial ring and pleural furrows of

Homalonotid trilobites from the Silurian and Lower Devonian

major and kinglakensis are comparable, although those of

major do not appear to shallow abaxially. The specimen has 10

axial rings, although the posterior part of the pygidium is

broken off and whether there were further rings or a postaxial

ridge cannot be determined. On these few features the species

is only doubtfully assigned to Edgillia.

Gill (1949) considered Trimerus C Edgillia ) kinglakensis to

be most closely related to, and directly descended from, the

earliest Ludlow T. (T.) vomer. Gill constructed his phylogeny

erroneously considering these species to be much closer in age

than they actually are. Redescription of both vomer and

kinglakensis shows that these species are not closely related.

T. (T.) vomer is a highly derived species and kinglakensis

exhibits none of its characteristic features. With respect to the

presumably ancestral T. ( Ramiotis ), morphoclines of increasing

glabellar complexity defining T. ( Trimerus ) are contrary to

morphoclines of decreasing glabellar complexity characterising

T. ( Edgillia ) and suggest independent derivation of these

subgenera.

Trimerus {Edgillia) kinglakensis (Gill, 1949)

Figures 5A, 5D, 16, 17.1-17.7

Homalonotus sp. — Gill, 1947: 13.

Trimerus kinglakensis Gill, 1949: 67, pi. 8 figs 1-3, pi. 9 figs 3, 5-6,

text-fig. IE. — Williams, 1964: table 1. — Wenndorf, 1990: 16. — Jell,

1992: 11, text-fig. IB .— Schraut, 2000: 382.

Type material. Holotype NMV P14580 (cephalon, figured Gill, 1949:

pi. 8 figs 1, 2, pi. 9 fig. 3, text-fig. IE, Fig. 16.12 herein, counterpart

previously registered NMV P14581) from PL252, Williams locality

W3, Middendorps Quarry, Kinglake West, Victoria. Paratype NMV

P14582 (thoracopygon, figured Gill, 1949: pi. 8 fig. 3, counterpart

previously registered NMV P14583) from PL252. For locality see

Fig. 11.

Previously jigured material. NMV P14584 (thoracopygon, figured

Gill, 1949: pi. 9 fig. 5), NMV P14585 (pygidium, figured Gill, 1949:

pi. 9 fig.6, counterpart previously registered NMV P14586) from

PL252.

Registered material. 307 specimens: 2 dorsal exoskeletons, 22 articu-

lated thorax-pygidia with displaced cephala, 29 articulated thoraxes

with displaced cephala, 12 articulated thorax-pygidia with inverted

cephala, 3 articulated thoraxes with inverted cephala, 3 articulated

thoraxes with displaced cephala and pygidia, 110 articulated or partly

disarticulated thoraxes with attached pygidia, 10 articulated or partly

disarticulated thoraxes with displaced pygidia, 32 cephala, 4 cranidia,

1 librigena, 30 articulated or partly disarticulated thoraxes, 50 pygidia.

NMV P149634, P149635, NMV P305248-P305545 from PL252.

NMV P305546 from “Kinglake”, Victoria. NMV P305547 from “King

Parrot Creek”, Kinglake West. NMV P304849 from PL6640, Garratt

locality M8, Heathcote Junction. NMV P304850 from PL6641,

Williams locality G96, Clonbinane. NMV P304853, P304854? from

PL6645, Williams locality W47, Humevale. NMV P304852? from

PL6648, Humevale. NMV P304857? from PL6659, Williams locality

W8, Kinglake West. NMV P304856 from PL6660, Humevale.

Unregistered specimen from PL229, Williams locality W7, Collins

Quarry, Kinglake West. For localities see Fig. 11. NMV

P305548-P305550 from “Christmas Hills”, Victoria (probably in the

vicinity of PL261). For locality see Jell and Holloway, 1983: fig. 1.

NMV P305551, P305552 from old Scoresby Brick Pit, Wantirna

South, Victoria.

Stratigraphic distribution. Humevale Siltstone (from basal horizons

at the old Scoresby Brick Pit to the Collins Quarry Sandstone Member

at the top of the unit), upper Notoparmella plentiensis-Boucotia janae-

Boucotia australis assemblage zones, Pfidoli -Lochkovian.

Revised diagnosis. Cranidial width 1.5 times length. Glabella

trapezoid, length more or less equal to width, sides straight,

converging at about 15°, anterior margin well defined.

Proximal section of SI moderately impressed, directed diag-

onally, glabellar lobation otherwise poorly defined.

Preglabellar field 0.2 times cranidial length. Palpebral lobes

placed opposite glabellar midlength/0.4 cranidial length and

remote (5-6 1.55 times preoccipital glabellar width). Anterior

branches of facial suture angular, parallel to axial furrows for a

short distance posteriorly, converging at about 80° anteriorly.

Librigenal border furrow weakly defined. Course of rostral

suture angular, defining an obtuse angle of about 140°, dorsal

section of rostral plate boomerang-shaped. Hypostome with

middle furrow very deep, posterior border with wide, short

triangular lobes (length 0. 1 times hypostomal length) and deep,

angular medial notch. Pygidium triangular, length 0.95 times

width, with long pointed tip, sides straight, converging at about

75°. Axial furrows moderately impressed opposite first ring,

deep posteriorly. Axial width 0.45 times pygidial width. 13-14

axial rings. 7 pleural ribs, rib-ring medially offset at third rib,

pleural furrows markedly shallowing abaxially. Dorsal

exoskeleton very strongly pitted.

Description. Exoskeleton large, maximum size estimated 25 cm (from

NMV P305258), occipital/pygidial convexity (tr.) moderate. Pygidial

and librigenal doublure and hypostome finely ornamented with short

ridges.

Cephalon with rounded triangular outline with weakly convex

sides, converging forwards at about 70° opposite genal field and at

115° opposite rostral plate, length 0.66 times width. Glabellar length

about equal to width (although difficult to quantify due to the poor

definition of the axial furrows posteriorly), width about 0.5 times

cranidial width, sides straight to weakly convex, length 0.8 times cra-

nidial length, anterior margin transverse, medial indentation moder-

ately impressed to absent. Glabellar lobation very weakly defined,

generally only the proximal part of SI distinct, S2 distinct only on

smallest specimens (e.g. NMV P305272, see Fig. 16.10). S3 indistinct.

Occipital ring 0.1 times cranidial length, slightly wider medially.

Occipital furrow deep with weak forward flexure medially. LI 0.35

times glabellar length. SI strongly convex, weakly impressed to indis-

tinct adjacent to axial furrow, moderately impressed and directed

diagonally (posteromedially) abaxially. S2 a very weak depression

adjacent to axial furrow or indistinct, rarely extending adaxially, trans-

verse. Axial furrows shallow to indistinct and directed obliquely oppo-

site paraglabellar area and across occipital furrow, deep anteriorly.

Paraglabellar area weakly defined. Preglabellar field flat (tr. sect.).

Length (exsag.) of posterior border equal to occipital length adaxially,

lengthening to 1.5 times occipital length abaxially. Posterior border

furrow transverse, very wide, moderately impressed, terminating dis-

tally. Postocular fixigenal area long, length (exsag.) 0.21 times cran-

idial length. Palpebral lobe 0.14 times cranidial length, 6-6 1.64 times

glabellar width, palpebral furrow indistinct. Preocular fixigenal area of

moderate width, 0.17 times 6-5, narrowing markedly anteriorly, eye

ridges not distinct. Anterior branches of facial suture meeting connec-

tive sutures opposite 0.9 cephalic length. Librigena with wide, moder-

ately impressed border furrow anterior of eye, not defined opposite

preglabellar field, librigenal field weakly convex, steeply inclined.

Homalonotid trilobites from the Silurian and Lower Devonian

Dorsal section of connective sutures diverging at about 90°. Dorsal

surface of rostral plate length (sag.) 0.5 times cranidial length, very

weakly concave (tr. sect.). Rostral suture moderately convex. Ventral

surface of rostral plate kite-shaped, with length 0.9 times width,

posterior width 0. 1 maximum times width. Connective sutures angular,

anterior section converging posteriorly at about 30°, posterior section

converging posteriorly at about 70°. Librigenal doublure with wide,

shallow vincular furrow, indistinct anteriorly. Hypostomal suture

broadly concave.

Hypostome with length 0.75 times width, anterior wings large,

width 0.35 times hypostomal width.

Thorax with thirteen segments. Axial furrows defined by shallow to

moderately impressed, diagonally directed furrows on each segment,

each meeting posterior margin at indentation that correspond to deep

pits (axial articulating process) on internal mould. Pleural furrows

wide and deep, pleural tips rounded.

Pygidium triangular, with sides weakly concave. Pygidial axis with

sides straight and tapering at about 30°. Axis reaching 0.85 times

pygidial length. Terminal piece parabolic in outline, length 0.08 times

axial length, posterior margin moderately to weakly defined. Postaxial

ridge not defined. Ring furrows short (sag.) and deep. Pleural furrows

wide and deep adjacent to axial furrows, shallowing markedly abaxial-

ly, reaching wide and very shallow border furrow. Interpleural furrows

very weakly defined. Border weakly defined. Pygidial doublure flat

and weakly inclined posteriorly, laterally with angular profile (tr.

section), distal surface horizontal, proximal surface increasingly

inclined anteriorly. In posterior view anterior margin of pygidium

moderately convex, posterior margin without distinct medial arch.

Remarks. Gill’s (1949) original description is not detailed but

documents most of the characters listed in the revised diag-

nosis. Gill described the glabellar furrows as absent, but the

proximal portion of SI is manifest as a short, moderately

impressed diagonal furrow.

Trimerus ( Edgillia ) kinglakensis can be closely compared to

the poorly known T. (E) vanuxemi from the Helderbergian of

North America. In addition to the shared cephalic and pygidial

features listed above as defining T. {Edgillia), the species share

a forwardly convex rostral suture, a similar pygidial rib-ring

offset (third-fourth? rib). The species differ in that vanuxemi

exhibits longer glabellar proportions, shorter cephalic and

pygidial proportions, a greater number of pleural ribs, a wider

pygidial axis, and lacks a produced pygidial tip. In the depth of

the pygidial axial furrows and ring and pleural furrows,

kinglakensis shows closer resemblance to T. (E?) major , also

from the Helderbergian of North America. However, major

differs from kinglakensis in that the pleural furrows do not

shallow abaxially. Pygidial morphology of the Late Silurian

T. (E.) mongolicus is closely comparable to that of kinglaken-

sis. The Mongolian species exhibits similar proportions, 13

pygidial axial rings, deep ring furrows and shallow pygidial

pleural furrows and an acuminate tip. T. (E.) kinglakensis

differs in having deeper pygidial axial furrows, a shorter

preglabellar field, and in the strong convexity of the rostral

suture. Although the course of the rostral suture has been

emphasised in the diagnoses of higher taxa (e.g. medial flexure

in Burmeisteria, concavity in Digonus: see discussion above),

variability in the forward curvature of the rostral suture

amongst Trimerus is considered only of specific significance.

Apart from kinglakensis and vanuxemi, few species of Trimerus

exhibit strongly forwardly convex rostral sutures, the most

notable exceptions being the type species T. (T.) del-

phinocephalus and T. (T) flexuosus. Other features of these

latter species are considered characteristic of T. ( Trimerus )

and T. {Ramiotis) respectively, and indicate that they are not

closely related to kinglakensis.

Environmental notes. See discussion on taphonomy and bio-

facies. Trimerus {Edgillia) kinglakensis is considered to have

inhabited mid- to outer-shelf environments.

Trimerus ( Edgillia ) jelli sp. nov.

Figure 17.8-17.19

Homalonotidae gen. et sp. indet. 3 — Holloway and Neil, 1982: 146,

fig. 4M-R.

Type material. Holotype NMV P82873 (pygidium) from PL2288,

Thomas locality F25, Parish of Redcastle, Heathcote, Victoria (Fig.

17.9). Paratypes NMV P78300 (ex GSV48930, figured Holloway and

Neil, 1982: fig. 4R), NMV P304610 (cranidia), NMV P304612

(thoracic segment), NMV P78298 (pygidium, ex GSV48942, figured

Holloway and Neil, 1982: figs 4M, 4N, 4Q) from PL2319, Thomas

locality F55, Parish of Redcastle, Heathcote. Paratypes NMV P304638

(cranidium), NMV P304633-4 (librigenae), NMV P304635 (hypos-

tome), NMV P304636, P304637 (thoracic segments), NMV P304639

(pygidium) from PL6652, Heathcote. Paratype NMV P78299 (libri-

gena, figured Holloway and Neil, 1982: figs 40, 4P) from PL2288. For

localities see Fig. 8.

Registered material. 45 specimens: 6 cranidia, 3 librigenae, 1 hypos-

tome, 25 thoracic segments, 8 pygidia. NMV P82925 (ex GSV48928),

NMV P3 046 1 0-P3 0462 5 , NMV P304626 (ex GSV48933),

GSV48944, GSV48938 from PL2319. NMV P82873, NMV

P304628-P304632 from PL2288. NMV P304633-P304647 from

PL6652. Unregistered specimen from PL2328, Heathcote.

Figure 16. Trimerus {Edgillia) kinglakensis (Gill, 1949). 1, NMV P305261, cranidium, dorsal view x 0.6 (internal mould) from PL252. 2a, NMV

P305257, cephalon and hypostome, dorsal view of cephalon x 0.75 (latex cast) from PL252. 2b, same, dorsal view of hypostome x 1.6. 2c, same,

ventral view of cephalon (doublure) and hypostome x 1.4. 3, NMV P305256, cephalothorax, dorsal view of cephalon x 0.85 (latex cast) from

PL252. 4, NMV P305262, cephalon, dorsal view x 0.85 (latex cast) from PL252. 5, NMV P305265, cephalon, hypostome and displaced thora-

copygon, dorsal view of hypostome x 1.55 (latex cast) from PL252. 6a, NMV P305250, cephalon, dorsal view x 0.95 (latex cast) from PL252.

6b, same, lateral view x 1.0. 7a, NMV P305264, pygidium, posterodorsal view x 0.85 (latex cast) from PL252. 7b, same, lateral view x 1.4. 8,

NMV P305248, cephalon, ventral view (doublure) x 1.0 (latex cast) from PL252. 9, NMV P305252, cephalon, oblique view x 0.7 (internal mould)

from PL252. 10, NMV P305272, cephalon, dorsal view x 3.1 (internal mould) from PL252. 11, NMV P305260, thoracopygon, dorsal view of

pygidium x 0.7 (latex cast) from PL252. 12, holotype NMV P14580, cephalon, dorsal view x 0.75 (internal mould) from PL252. 13, NMV

P305258, thoracopygon, dorsal view x 0.6 (latex cast) from PL252. 14a, NMV P305263, pygidium, dorsal view x 1.1 (latex cast) from PL252.

14b, same, x 1.0 (internal mould). 15, NMV P305253, cephalon, ventral view (doublure) x 1.6 (latex cast) from PL252. 16, NMV P305254,

cephalon, dorsal view, enlargement of anterior margin x 2.9 (latex cast) from PL252.

Andrew C. Sandford

Homalonotid trilobites from the Silurian and Lower Devonian

Stratigraphic distribution. Stoddart Member, Mt Ida Formation, 200 m

to 500 m above the base of the unit, Boucotia australis Assemblage

Zone, mid-late Lochkovian.

Derivation of name. For Peter Jell (Queensland Museum), for

his contribution to Victorian palaeontology.

Diagnosis. Glabella with very weakly defined lobation, sides

straight and converging at about 15°, anterior margin well

defined, transverse, with broad medial depression. Axial fur-

rows poorly defined posteriorly. Preglabellar field long, length

0.45 times anterior width of glabella (estimated 0.25 times

cranidial length). Anterior branches of facial suture converging

at 40°. Anterior margin of cranidium (including rostral suture)

transverse. Palpebral lobe placed with midline opposite

(estimated) 0.35 cranidial length. Hypostome with large, broad-

based rounded lobes on the posterior margin. Thoracic pleurae

with bilobed tips. Pygidium triangular, length equalling width,

sides straight, converging at 60°. Axis with 10 rings, width 0.46

times pygidial width, length 0.8 (estimated) times pygidial

length. Axial furrows very shallow. 6 pleural ribs. Pleural off-

set at third rib. Ring furrows moderately impressed, pleural

furrows very shallow to indistinct, increasingly so posteriorly.

Discussion. Although most specimens assigned to this species

are fragmentary, the morphology is distinctive enough to

warrant description. The weakly convergent glabellar sides, the

transverse and well-defined anterior margin and the simple

glabellar morphology support assignment to Edgillia.

In cephalic features Trimerus { Edgillia ) jelli differs from

T. (E.) kinglakensis and T. (E.) vanuxemi in the transverse

course of the rostral suture. Pygidial axial, ring and pleural

furrows of vanuxemi are moderate to shallow in depth. In

kinglakensis , the axial furrows and ring furrows are deep, with

pleural furrows shallower, and markedly shallowing distally.

The pygidium of jelli also exhibits pleural furrows shallower

than the ring furrows, but is distinctive in that the pleural

furrows are very shallow. The weakly defined segmentation is

comparable to that of the Llandovery-lower Wenlock species of

T. ( Ramiotis ), although jelli differs from these in having a more

elongate pygidial outline and in lacking the raised postaxial

ridge typical of T. {Ramiotis). In these respects the pygidia of

jelli more closely resemble pygidia of species assigned in this

work to Burmeisteria, in particular B. clarkei and B. linares.

However, the strong segmentation shared by clarkei and linares

suggest that similarities in the pygidial outline and depth of

pygidial axial ring and pleural furrows are not of high taxo-

nomic significance. The distinctive (straight-sided, weakly

furrowed) pygidial morphology shared by these three taxa and

others such as as Dipleura garratti suggests the morphology is

homologous.

Hypostomes are known for few species of Trimerus. The

hypostome of T. {Edgillia) jelli (Fig. 17.12) closely resembles

that of T. {E.) kinglakensis (Fig. 16.2). These both differ from

the hypostome of T. (T.) delphinocephalus (Whittington, 1993:

fig. IB) and T. {Ramiotis) rickardsi (Fig. 18.6) in having larger

posterior border lobes and deeper middle furrows.

Environmental notes. Trimerus {Edgillia) jelli is considered to

have inhabited high-energy, very shallow environments.

Trimerus ( Ramiotis ) subgen. nov.

Type species. Trimerus ( Ramiotis ) rickardsi sp. nov., from the upper

Llandovery ( crenulata Biozone) Chintin Formation, central Victoria,

Australia.

Other species included. Platycoryphe dyaulax Thomas, 1977, Trimerus

( Ramiotis ) iani sp. nov., T. permutus Tomczykowa, 1978 (nom. nov.

for T. lobatus Tomczykowa, 1975 non Prouty, 1923), T. (R.) otisi sp.

nov., T. {R.) tomczykowae sp. nov., T. (R.) thomasi sp. nov., T. sp. {in

Edgecombe and Fortey, 2000), T. sp. {in Curtis and Lane, 1998), T. sp.

A (in Wolfart, 1961),

Other species tentatively included. Dipleura salteri Morris, 1988

(nom. nov. for Homalonotus {Koenigia) ludensis Salter (1865) non H.

ludensis Murchison, 1839).

Range. Silurian.

Derivation of name. For my son Otis Rami.

Diagnosis. Glabella trapezoid or weakly expanded across Ll-

L1 (tr.), low, with sides more or less straight and weakly to

moderately convergent. SI -S3 weakly impressed. Preglabellar

field of short to moderate length (~0. 15-0.25 times cephalic

length). Hypostomal middle furrow shallow. Pygidium short,

length 0.5-1.0 times width. Postaxial ridge raised. Pygidium

with moderately acute to obtusely convergent sides (>70°), tip

without process or spine. Pygidial border furrow and ridge-like

border present in late species.

Figure 17.1-17.7 Trimerus {Edgillia) kinglakensis (Gill, 1949). 1, NMV P305264, thoracopygon, dorsal view x 0.65 (latex cast) from PL252. 2,

NMV P14584, inverted cephalon and displaced thoracopygon, dorsal view of cephalon x 0.9 (internal mould) from PL252. 3, NMV P305276,

cephalon and displaced, incomplete thorax, ventral view of cephalon (doublure) x 1.6 (latex cast) from PL252. 4, NMV P305269, incomplete

thoracopygon, ventral view of pygidium (doublure) x 0.85 (latex cast) from PL252. 5, NMV P305252, cephalon, lateral view x 0.6 (internal

mould) from PL252. 6, NMV P305255, cephalon and displaced thorax, dorsal view of cephalon x 0.85 (latex cast) from PL252. 7, NMV P305258,

thoracopygon, dorsal view of pygidium x 0.95 (latex cast) from PL252.

Figure 17.8-17.19 Trimerus {Edgillia) jelli sp. nov. 8, paratype NMV P304612, thoracic segment, dorsal view x 1.55 (internal mould) from

PL2319. 9, holotype NMV P82873, pygidium, dorsal view x 1.4 (internal mould) from PL2288. 10, paratype NMV P304636, thoracic segment,

lateral view x 2.0 (internal mould) from PL6652. 11, paratype NMV P304637, thoracic segment, lateral view x 1.9 (internal mould) from PL6652.

12, paratype NMV P304635, hypostome, ventral view x 2.0 (internal mould) from PL6652. 13a, paratype NMV P304610, cranidium, dorsal view

x 1.3 (latex cast) from PL2319. 13b, same, x 1.35 (internal mould). 14a, paratype NMV P304634, librigena, dorsal view x 1.45 (latex cast) from

PL6652. 14b, same, lateral view x 1.4. 15, paratype NMV P78300, cranidium, dorsal view x 1.1 (internal mould) from PL2319. 16a, paratype

NMV P78298, pygidium, dorsal view x 1.25 (internal mould) from PL2319. 16b, same (latex cast). 16c, same, ventral view (doublure) x 1.0

(internal mould). 16d, same, lateral view x 1.0. 17, paratype NMV P304638, cranidium, dorsal view x 1.25 (internal mould) from PL6652. 18,

paratype NMV P304633, librigena, ventral view (doublure) x 1.25 (latex cast) from PL6652. 19, paratype NMV P304639, pygidium, dorsal view

x 5.5 (internal mould) from PL6652.

Andrew C. Sandford

Discussion. Thomas (1977) noted that the rarity of Ashgill and

Llandovery homalonotids emphasised the morphological gap

between Ordovician and post-Ordovician genera. Reed (1918)

suggested that links between Wenlock Trimerus and

Ordovician homalonotid groups might be found in Llandovery

strata. In this context Thomas interpreted his new Saudi

Arabian Llandovery species Platycoryphe dyaulax as showing

features of both Platycoryphe/Brongniartella and Trimerus.

Thomas suggested that post-Ordovician homalonotines were

derived from Platycoryphe/Brongniartella stock, rather than

from Eohomalonotus as suggested by Sdzuy (1957). In assign-

ing dyaulax to Platycoryphe , Thomas emphasised its wider and

rounded pygidial outline, contrasting with the longer and

posteriorly pointed outlines of ‘typical’ Trimerus, i.e.

T. (Trimerus). Pygidia of dyaulax also exhibit shallow ring

furrows and very shallow to effaced axial and pleural furrows,

whereas pygidia of T. ( Trimerus ) exhibit pleural and ring

furrows of moderate depth, and of equal depth.

New species from the Llandovery and lower Wenlock of

south-eastern Australia show strong resemblances to

Platycoryphe dyaulax and define a tight species group.

Similarities in cephalic morphology between dyaulax and

Trimerus noted by Thomas are emphasised by the new

Llandovery- Wenlock taxa, and all share weakly tapering,

straight- sided, trapezoid glabellar outlines. The new south-

eastern Australia taxa exhibit pygidial proportions and segmen-

tation intermediate between dyaulax and T. ( Trimerus ) and

support Thomas’s suggestion of close affinities between

dyaulax and Trimerus. These similarities, and the weak defini-

tion of thoracic trilobation, the width of the thoracic axis and

the lower degree pygidial segmentation are emphasised here

to justify assignment of dyaulax to Trimerus rather than to

Platycoryphe or Brongniartella. T. (Ramiotis) is erected

to embrace this group of species, which includes late

Llandovery T. (R.) rickardsi from Victoria and T. (R.) iani

from Tasmania, and the early Wenlock T. (R.) tomczykowae

from Victoria.

In pygidial outline and segmentation there is a morpho-

logical gradient through time from Trimerus (Ramiotis)

dyaulax (mid Llandovery) to T. (R.) rickardsi and T. (R.) iani

(late Llandovery) with moderately impressed ring and axial

furrows and shallow pleural furrows, to T. (R.) tomczykowae

(early Wenlock) with pygidial furrows of subequal and moder-

ate depth, and to T. (Trimerus) (Wenlock-early Ludlow).

Although T. (Trimerus) appears to be derived from this group,

there are a number of new or poorly known Ludlow-Pndolf

Trimerus that share the distinctive cranidial morphology of the

Llandovery-Wenlock T. (Ramiotis). In exhibiting elongate

glabellar proportions, weakly tapered, straight-sided trapezoid

glabellar outlines, low glabellar profiles and preglabellar

fields of moderate length, these species are compatible with

assignment to T. (Ramiotis) rather than to T. (Trimerus). These

species include T. (R.) otisi and T. (R.) thomasi from Victoria,

T. (R.) permutus from Poland, and T. (R.) sp. (in Wolfart, 1961)

from Bolivia. Compared with the Llandovery-Wenlock

T. (Ramiotis), these Ludlow-Pndolf species encompass a wider

range of pygidial morphologies, particularly in length:width

proportions and depth of pygidial furrows.

Trimerus (Ramiotis) is easily distinguished from T.

(Trimerus) in that it lacks most of the characteristic cephalic

and pygidial features of the latter. Of the suite of features

listed as diagnostic for T. (Trimerus), only T. (R.) permutus

exhibits strongly expressed glabellar lobation. Several species

exhibit sagittal glabellar ridges (albeit weak), several

species exhibit distinct medial indentations of the anterior

glabellar margin, and some specimens of T. (R.) otisi show a

tendency towards outlines expanded across LI -LI (tr.) and

strongly tapered glabellar outlines. However, there are no

species of T. (Ramiotis) that exhibit a more than a few of the

characters of T. (Trimerus), justifying the grouping of the latter.

However, with the exception of the deep pygidial border furrow

and raised border, the characters distinguishing T. (Ramiotis)

from T. (Trimerus) can be considered as primitive, and hence

only subgeneric status is justifiable.

Dipleura salteri Morris, 1988 from the upper Ludlow

(Ludfordian) of England is a poorly known species represented

by a single cranidium (see Salter, 1865: p. 121, pi. 12 fig. 1).

Following Salter’s (1865) suggestion, Tomczykowa (1975) and

Morris (1988) assigned the species to Dipleura, but the forward

eye position, the long preglabellar field and the quadrate course

of the preocular facial sutures preclude assignment to that

genus and are in accord with assignment to Trimerus.

Subgeneric assignment of salteri is difficult as the species

exhibits a very strongly tapered glabellar outline comparable to

that of T. (Trimerus), but lacks the other diagnostic glabellar

features of the subgenus such as the outline strongly expanded

across Ll-Ll (tr.) and the distinct lobation. However, the strong

tapering of the glabella may be partly attributable to sagittally

oriented tectonic compression evident in the apparent con-

cavity (sag.) of the preglabellar field. In all other respects the

specimen is compatible with assignment to T. (Ramiotis), to

which it is tentatively assigned.

Trimerus (Ramiotis) dyaulax is from the Aeronian (mid-

Llandovery) convolutus Biozone. A possibly earlier origin for

Trimerus is suggested by a poorly known species from the

lower Llandovery of Paraguay. Wolfart (1961) assigned the

several cranidia representing this species to Trimerus. In having

elongate glabellar proportions, weakly tapered, straight-sided

trapezoid glabellar outlines, weak glabellar lobation and a

preglabellar field of moderate length, these can be assigned to

T. (Ramiotis). The only other Llandovery T. (Ramiotis) is rep-

resented by fragmentary pygidia from the Aeronian of Wales,

documented as T. sp. by Curtis and Lane (1998). Although

closer in age to dyaulax, the Welsh species differs markedly

from it in having moderately impressed pleural, ring and axial

furrows, in this respect closely resembling T. (R.) rickardsi.

Trimerus ( Ramiotis ) rickardsi sp. nov.

Figure 18

Type material. Holotype NMV P305556 (cephalon) from PL6361,

Springfield, Victoria (Fig. 18.1). Paratypes NMV P305553, P305554,

NMV P305557, NMV P305563 (cephala), NMV P305559-P305562,

NMV P305564 (cranidia), NMV P305582 (thoracic segment), NMV

P305572-P305574 (pygidia) from PL6361. Paratype NMV P138204

(pygidium) from PL667, Springfield. Paratype NMV PI 38207

(pygidium) from PL599, Springfield. Paratypes NMV P147779

Homalonotid trilobites from the Silurian and Lower Devonian

(hypostome), NMV P147772 (pygidium) from PL256, Wallan,

Victoria. For localities see Fig. 11.

Registered material. 66 specimens. 5 cephala, 15 cranidia, 6 librigenae,

1 rostral plate, 3 hypostomes, 12 thoracic segments, 24 pygidia. NMV

P305553-P305593 from PL6361. NMV P305626-P305628 from

PL6390, Springfield. NMV P138213, NMV P147771, P147772, NMV

P147774-P147777, NMV P147779-P147780, NMV P1477787 from

PL256. NMV P 1 39442-P 1 39446, NMV P305595 from “Lancefield”,

Victoria. NMV PI 38205-PI 38207, NMV P138270 from PL599. NMV

P138204, NMV P305594 from PL667. NMV P138267, NMV P147778

from PL1964, GSV locality B25, Springfield. Lithological similarities

suggests that the specimens labelled as coming from “Lancefield”

almost certainly come from the Parish of Goldie, and possibly in the

vicinity of allotments B19 and B23 (see Thomas, 1960: 1:31, 680

Lancefield Geological Sheet).

Stratigraphic horizon. Chintin Formation, upper Llandovery. Rickards

and Sandford (1998) suggested equivalence to the upper crenulata

Biozone, based on the presence of Acemaspis sp. within the unit, and

on the occurrence of crenulata Biozone graptolites in the uppermost

beds of the underlying Springfield Sandstone.

Derivation of name. For R. B. Rickards (University of

Cambridge), for his contribution to Victorian palaeontology.

Diagnosis. Cephalon rounded pentagonal, width about 1.6

times length, sides converging at 60° posteriorly, at 125° anter-

iorly. Glabella trapezoid, length 1.2 times width, sides sub-

parallel opposite paraglabellar areas, converging anteriorly at

about 22°. S1-S3 moderately impressed adjacent to the axial

furrow, shallow adaxially. Preglabellar field long, 0.23 times

cephalic length. Palpebral lobes placed opposite 0.42 cranidial

length/0.52 glabellar length. Anterior branches of facial suture

straight, converging at about 45°, anterior-most section curving

gently to the diagonal, continuous in curvature with broadly

rounded rostral suture. Dorsal section of rostral plate cres-

centic, length 0.1 times cephalic length. Ventral section of

rostral plate with length 0.92 times width, connective sutures

converging posteriorly at 50°. Posterior border of hypostome

with short lobes of length 0.1 times hypostomal length.

Pygidium wide, length 0.78 times width, with sides weakly

convex, converging posteriorly at about 100°. Pygidial axis

0.42 times pygidial width, with 10 axial rings. Axial furrows

straight, tapering at about 30°, shallow anteriorly, moderately

impressed posteriorly. Ring furrows deep to moderately

impressed, pleural furrows shallow. 7-8 ribs, rib-ring medially

offset at fourth rib.

Description. Exoskeleton small, maximum length 12 cm (estimated

from NMV P138204), occipital and pygidial convexity (tr.) moderate.

Dorsal exoskeleton and doublure finely granulose.

Cranidium with length (sag.) 0.9 times cephalic length. Glabella

trapezoid, length about 0.77 times cranidial length, width about 0.43

times cranidial width, anterior margin moderately well defined,

broadly rounded, medial indentation variably expressed (indistinct to

strong, e.g. NMV P305559). Glabellar lobation well defined. Occipital

ring 0.09 times glabellar length, slightly wider medially. Occipital

furrow deeply impressed with broad forward flexure medially. LI ~0.3

times glabellar length, L2 and L3 -0.1 times glabellar length and

frontal lobe -0.25 times glabellar length. S 1 weakly convex forwards

and directed posteromedially at about 25° from the transverse. S2

transverse. S3 directed antero-medially at about 10° from the trans-

verse. Axial furrows moderately impressed opposite genae, shallow

and directed diagonally opposite occipital ring. Paraglabellar area very

weakly defined. Length (exsag.) of posterior border equal to occipital

length adaxially, lengthening (exsag.) markedly abaxially to about

twice occipital length. Posterior border furrow transverse, very wide,

moderately impressed, terminating distally. Postocular fixigenal area

with length (exsag.) 0.22 times cranidial length. Palpebral lobe

short, 0. 1 times cranidial length, placed with 6-8 about 1 .77 times pre-

occipital glabellar width/0.74 times cephalic width. Palpebral furrow

wide and shallow. Preocular fixigenal area narrow (tr.), 0.17 times 8-5,

uniform in width anteriorly. Preglabellar field flat (tr. sect.). Anterior

branches of facial suture straight from eye to a point opposite

midlength (sag.) of preglabellar field, anterior section curved.

Librigenal border furrow wide and shallow opposite genal field, not

defined opposite preglabellar field, border furrow indistinct on fixi-

genae. Lateral border narrow and convex, narrowing posteriorly, indis-

tinct opposite preglabellar field and on fixigenae. Dorsal surface of

rostral plate with length 0.13 times width, anterior margin rounded.

Dorsal section of connective sutures diverging forwards at about 30°.

Ventral surface of rostral plate flat (tr, sag. sect.), kite-shaped, sides

very weakly sinusoidal. Librigenal doublure without distinct vincular

furrow. Hypostomal suture transverse.

Hypostome with moderately impressed middle furrow.

Thoracic segments with wide (sag.), deep articulating furrows, deep

and narow (exsag.) pleural furrows. Axis very weakly defined by very

shallow, wide, diagonally directed furrow. Pleural tips weakly bilobed

with larger lobe opposite posterior band and smaller lobe opposite

anterior band.

Pygidium triangular. Pygidial axis extending to about 0.9 pygidial

length, with semicircular terminal piece, length 0.1 times axial length,

continuous posteriorly with raised postaxial ridge. Ring furrows deep

to moderately impressed, pleural furrows shallow. Furrows markedly

shallower on external casts. Pleural furrows not reaching margin.

Border furrow and border poorly defined. In posterior view posterior

margin of pygidium horizontal. In lateral view dorsal profile of axis

moderately convex, postaxial ridge steeply inclined.

Discussion. Trimerus ( Ramiotis ) rickardsi is the most com-

pletely known homalonotid from the Llandovery. The species is

of primary significance in the understanding of relationships

between poorly known Llandovery homalonotids and better-

known Wenlock and Ludlow taxa.

In pygidial morphology Trimerus ( Ramiotis ) rickardsi is

typical of other Llandovery- Wenlock species, particularly in

having short pygidial proportions and much shallower ring

furrows relative to the pleural furrows. In the latter feature

rickardsi most closely resembles the very poorly known Welsh

T. (R.) sp. (see Curtis and Lane, 1998), but can be distinguished

by its higher segmentation (7 rings, 6 ribs in T. (R.) sp., cf. 10

rings, 8 ribs in rickardsi ). T. (R.) dyaulax differs from rick-

ardsi in having even shorter proportions, a rounded pygidial

tip, a low postaxial ridge, even shallower axial, ring and

pleural furrows and lower segmentation (6 rings, 5 ribs) than

counted for rickardsi. Pygidial morphology of T. (R.) iani from

the upper Llandovery of Tasmania is poorly known. The single

pygidium known exhibits segmentation comparable (9 rings, 6

ribs) to that of rickardsi, but differs in having shorter propor-

tions and a rounded tip. The relative depth of the ring furrows

compared to the pleural furrows distinguishes rickardsi from

the Wenlock T. (R.) tomczykowae from Victoria, and from other

Ludlow species of T. {Ramiotis). T. (R.) tomczykowae further

differs in having a more rounded tip. Of the Upper Silurian

Andrew C. Sandford

Homalonotid trilobites from the Silurian and Lower Devonian

species, T. (R.) thomasi from Victoria differs markedly in

having elongate proportions (L:W~1.0), whilst pygidia of

T. (R.) otisi from Victoria differ markedly in the depth of the

pygidial pleural and ring furrows. Despite the pygidial differ-

ences, in the more elongate glabellar outline (LAV- 1.2) the

longer preglabellar field (0.25 cranidial length), and the expres-

sion of glabellar lobation, rickardsi shows closest resemblance

to otisi. T. (R.) rickardsi differs from most other T. ( Ramiotis )

in having a forwardly convex rostral suture, comparable to that

of the Llandovery Bolivian T. (R.) sp.

In having a relatively longer preglabellar field, lateral

glabellar furrows of moderate length, a weak sagittal glabellar

ridge and, in some specimens, a distinct medial indentation of

the anterior glabellar margin, and higher pygidial segmentation

Trimerus ( Ramiotis ) rickardsi shows closer affinities to

T. ( Trimerus ) than other Llandovery T. {Ramiotis). However, in

the absence of so many of the other derived features distin-

guishing T. (Trimerus), it would be over stated to regard

rickardsi as a transitional species between the subgenera.

Environmental notes. Articulated specimens are only known

from the type locality, and represented only by cephala. The

proportion of articulated and broken specimens is 13% respec-

tively, indicative of a taphofacies TII. Further east at PL256,

Wallan, breakage of T. (R.) rickardsi and other trilobites is

extremely high and indicates significant reworking. Associated

tempestite lithologies comprising thick coquinal bioclastic lags

and abundant mud rip-up clasts indicate deposition between

normal wave base and storm wave base. The trilobite fauna

may have been transport, possibly in a tempestite-generated

mass-flow, although the profound compositional differences

between the Springfield, Wallan and Lancefield faunas do not

support this and suggest distinct, depth-related assemblages.

Trimerus (Ramiotis) rickardsi is considered to inhabit inner

shelf environments.

Trimerus ( Ramiotis ) iani sp. nov.

Figures 19.1-19.4, 19.6

Trimerus sp. — Holloway and Sandford, 1993: 93, figs 4C-D, 4F-G,

4I-J, 4N-P, non fig. 4L.

Type material. Holotype NMV PI 37221 (cephalon lacking rostral

plate, figured Holloway and Sandford, 1993: 4F-G, 4J, Fig. 19.1 here-

in) from PL359, Tiger Range, northwest of Maydena, Tasmania.

Paratypes NMV PI 37222 (cranidium, figured Holloway and

Sandford: 41), NMV PI 37227 (pygidium, figured Holloway and

Sandford: 4N-P), NMV PI 37224 (cephalon, figured Holloway and

Sandford: 4C), NMV P137223 (cephalon and two displaced thoracic

segments) from PL359. For locality see Holloway and Sandford: fig. 1

Previously figured material. NMV PI 37225 (librigena, figured

Holloway and Sandford, 1993: 4D) from PL359.

Other material. NMV P137226 (cephalon) from PL359.

Stratigraphic distribution. As for Brongniartella sp.

Derivation of name. For my brother Ian.

Diagnosis. Cephalon rounded triangular, length -0.7 times

width, sides (opposite midlength) converging at -60°. Glabella

trapezoid in outline, length 1.2 times width, sides very weakly

concave and tapering at 20° anteriorly, anterior glabellar

margin transverse, without distinct medial indentation. SI -S3

and sagittal glabellar ridge very weakly defined. Preglabellar

field of moderate length (0.2 times cranidial length), rostral

suture transverse, dorsal section of rostral plate short, 0.05

times cephalic length. Eye placed opposite -0.5 cranidial

length (-0.6 glabellar length). Anterior branches of facial

sutures converging at 60°, curving abruptly adjacent to con-

nective sutures. Ventral surface of rostral plate elongate

pentangular in outline, with connective sutures converging pos-

teriorly at 45°. Pygidium short. Axis 0.45 times pygidial width,

raised posteriorly, 10 rings, ring furrows moderately impressed.

6 ribs, pleural furrows shallow. Axial furrows moderately

impressed.

Discussion. Trimerus (Ramiotis) iani is abundant at the type

locality. Holloway and Sandford (1993) were uncertain

whether the two dissimilar homalonotid pygidia from PL359

represented different species, or whether the differences were

attributable to size differences or deformation. In reviewing this

conclusion, I cannot attribute the contrast between the narrow,

concave- sided and strongly raised axis of the smaller specimen

(see Holloway and Sandford, 1993: fig. 4L) and the wide,

convex-sided and low axis of the larger specimen entirely to

deformation (see Fig. 19.6). The more elongate (length=width)

and parabolic outline and the indication of a distinct border

suggest that the smaller pygidium represents a separate species,

referable to Brongniartella (see above).

The diagnosis includes a number of features not listed in the

brief description of the species by Holloway and Sandford

(1993). Of the two cephala not figured by Holloway and

Figure 18. Trimerus (Ramiotis) rickardsi sp. nov. la, holotype NMV P305556, cephalon, oblique view x 1.7 (internal mould) from PL6361. lb,

same, dorsal view, lc, same (latex cast). 2, paratype NMV P305560, cranidium, dorsal view x 2.4 (latex cast) from PL6361. 3, paratype NMV

P305561, cranidium, dorsal view x 1.4 (internal mould) from PL6361. 4, paratype NMV P305557, cephalon, dorsal view x 2.1 (internal mould)

from PL6361. 5, paratype NMV P305564, cranidium, dorsal view x 2.1 (latex cast) from PL6361. 6, paratype NMV P147779, hypostome,

ventral view x 2.7 (latex cast) from PL256. 7, paratype NMV P305562, cranidium, dorsal view x 1.6 (internal mould) from PL6361. 8a, paratype

NMV P305559, cranidium, dorsal view x 1.5 (internal mould) from PL6361. 8b, same, x 1.6 (latex cast). 9, paratype NMV P305554, cephalon,

ventral view (doublure) x 1.75 (internal mould) from PL6361. 10a, paratype NMV P305582, thoracic segment, lateral view x 2.5 (internal mould)

fromPL6361. 10b, same, dorsal view x 2.2. 11, paratype NMV P305 5 63, cephalon, dorsal view x 2.4 (internal mould) fromPL6361. 12a, paratype

NMV P305553, cephalon, dorsal view x 1.5 (internal mould) from PL6361. 12b, same, lateral view x 2.0. 13a, paratype NMV P305573,

pygidium, dorsal view x 1.9 (latex cast) from PL6361. 13b, same, x 2.2 (internal mould). 14, paratype NMV P147772, pygidium, dorsal view

x 2.0 (latex cast) from PL256. 15, paratype NMV P138204, pygidium, dorsal view x 1.4 (internal mould) from PL667. 16, paratype NMV

P305574, pygidium, lateral view x 2.5 (latex cast) from PL6361. 17a, paratype NMV PI 38207, pygidium, dorsal view x 1.75 (latex cast) from

PL599. 17b, same, x 1.5 (internal mould). 17c, same, posterior view x 1.75. 17d, same, lateral view (latex cast). 18a, paratype NMV P305572,

pygidium, dorsal view x 1.6 (latex cast) from PL6361. 18b, same (internal mould).

Andrew C. Sandford

Homalonotid trilobites from the Silurian and Lower Devonian

Sandford, one specimen shows the anterior margin of the

cephalon, with the impression of the rostral suture evident on

the surface of the doublure (Fig. 19.4). The other speci-

men shows the posterior portion of the ventral surface of the

rostral plate. The pygidial pleural furrows are shallow, although

the greater depth of the first furrow appears to be partly

exaggerated by longitudinal shearing.

Holloway and Sandford (1993) distinguished Trimerus

( Ramiotis ) iani from previously documented homalonotids

from the Ludlow-Pragian strata of south-eastern Australia. Of

the species discussed by Holloway and Sandford, only speci-

mens described by Talent (1964) as “ Dipleura sp.” can be

referred to T. {Ramiotis).

In cephalic features Trimerus ( Ramiotis ) iani is similar to

T. (R.) otisi from the Ludlow of Victoria. These species share a

glabella with elongate proportions (L:W~1 .2) and moderately

tapering (-25°) and weakly concave sides, a preglabellar field

of similar length (0.2 cranidial length), similar cephalic propor-

tions (L:W ~0.7), a transverse rostral suture, very short

pygidial proportions and comparable pygidial segmentation.

T. (R.) otisi differs in having well defined glabellar lobation and

a distinctive tricuspid anterior cephalic margin. In cephalic

features T. (R.) permutus from the Ludlow of Poland is also

closely comparable, although it differs in having strongly

expressed glabellar lobation. In pygidial features iani demon-

strates its closer affinities to other Lower Silurian T. (Ramiotis),

particularly in the weak expression of the pleural furrows, the

deeper ring furrows, and the rounded tip. In pygidial morph-

ology iani is closest to T. (R.) dyaulax, that differs in having

weaker segmentation. T. (R.) iani is closest in age to the type

species T. (R.) rickardsi, but differs in having a shorter

preglabellar field, weaker glabellar lobation, a transverse

rostral suture, and a rounded pygidial tip.

Trimerus ( Ramiotis ) otisi sp. nov.

Figure 20

Homalonotus vomer . — Chapman, 1912: 298, pi. 63 fig. 1, non pi. 62

figs 2, 3, pi. 63 fig. 2.

Trimerus vomer . — Gill, 1949: 65, text-fig. IB, non text-fig. 1C.

Trimerus cf. lilydalensis. — Williams, 1964: 285, table 1.

Trimerus sp. — Garratt, 1968: 164, chart 1.

Trimerus cf. vomer . — Garratt, 1968: 164, chart 1.

Type material. Holotype NMV P304741 (cephalon and displaced tho-

racopygon) from PL1898, Eden Park, Victoria (Fig. 20.5). Paratypes

NMV P304727 (cephalon and displaced thoracopygon), NMV

P304722-P304724 (cephala), NMV P304726 (cranidium), NMV

P304718-P304720 (pygidia) from PL6633, Eden Park. Paratypes

NMV P304739, NMV P304797 (incomplete cephalothoraxes), NMV

P304738 (thoracopygon), NMV P304742 (pygidium) from PL1898.

Paratypes NMV P304730, NMV P304733, P304734 (cephala), NMV

P304729 (pygidium) from PL6632, Eden Park. Paratype NMV

P304737 (pygidium) from PL300, Clonbinane, Victoria. For localities

see Fig. 11.

Registered material. 141 specimens: 4 dorsal exoskeletons, 3 dorsal

exoskeletons with displaced cephala, 3 articulated cephalothoraxes, 2

thoraxes with displaced cephala, 15 cephala, 22 cranidia, 3 librigenae,

1 hypostome, 8 thoracic segments, 4 articulated thoraxes, 10 articulat-

ed thoracopygons, 66 pygidia. Eden Park: NMV P304766-P304770

from PL6627, Jutson locality VIII. NMV P304743, NMV P304775-

P304778 probably from PL6627. NMV P304771-P304773 from

PL6628. NMV P304832-P304836 from PL6629, Williams locality

F130. NMV P304745, NMV P304837-P304840 from PL6630. NMV

P304738-P304742, NMV P304779-P304799 from PL1898. NMV

P304832-P304838 from PL6631. NMV P304728-P304736, NMV

P304807-P304822 from PL6632. NMV P304718-P304727, NMV

P304747-P304765 from PL6633. NMV P304800-P304806 from

PL6635. NMV P304744 from “Eden Park”. Unregistered specimens

from PL6634 and PL6616, Williams locality XI 2. Upper

Plenty-Clonbinane area, Victoria: NMV P304774 from PL6636,

Jutson locality 111= Williams locality FI 2, Upper Plenty. NMV

P304746, NMV P304830, P304831 fromPL6638, Kenley locality 32g,

Upper Plenty. NMV P304844-P304846 from PL6639, Upper Plenty.

NMV P304841-P304843 from PL6642, Williams locality G23,

Wandong. NMV P304737, NMV P304823-P304826 from PL300.

NMV P304827-P304829 from PL1782, Clonbinane. In addition,

homalonotids recorded by Garratt (1968) from PL6618, Jutson

locality IX=Williams locality F90, Eden Park and by Williams (1964)

from Williams locality F41, Clonbinane undoubtedly refer to Trimerus

( Ramiotis ) otisi, although specimens from these localities are not rep-

resented in the MOV collections. Humevale: NMV P304851 from

PL6646, Williams locality W17. Unregistered specimen from PL6648.

For localities see Fig. 11.

Stratigraphic distribution. Eden Park Formation, from 350 m above

the base to the top of the unit, Notoparmella plentiensis Assemblage

Zone, late Ludlow.

Diagnosis. Cephalon with length 0.7 times width, anterior

margin tricuspid. Glabella trapezoid, length about 1.17 times

width, sides converging at about 25°, anterior margin strongly

defined, transverse. Glabellar lobation moderately well

defined. Palpebral lobe placed opposite 0.6 glabellar length

(0.5 cranidial length). Moderately impressed sutural and

Figure 19.1-19.4, 19.6. Trimerus ( Ramiotis ) iani sp. nov. la, holotype NMV P137221, cephalon, dorsal view (internal mould) from PL359.

lb, same, oblique view, lc, same, lateral view. Id, same, dorsal view (latex cast). 2, paratype NMV P137224, cephalon, dorsal view (internal

mould) from PL359. 3, paratype NMV P137222, cranidium, dorsal view (internal mould) from PL359. 4, paratype NMV P137223, cephalon,

dorsal view (internal mould) from PL359. 6a, paratype NMV P137227, pygidium (internal mould) lateral view, from PL359. 6b, same, posterior

view. 6c, same, dorsal view.

Figure 19.5, 19.8, 19.10, 19.12. Trimerus ( Ramiotis ) tomczykowae sp. nov. 5, paratype NMV P305191, cranidium, dorsal view x 1.1 (internal

mould) from PL2263. 8, holotype NMV P138203, pygidium (internal mould) x 1.5, from the “ Illaenus band”, Costerfield South. 8a, posterior

view. 8b, dorsal view. 8c, lateral view. 10, NMV P138291, cephalon (fragment), dorsal view (latex cast) from PL1460. 11, paratype NMV

P138293, rostral plate, dorsal view x 6.0 (latex cast) from PL1460.

Figure 19.7, 19.9, 19.11. Trimerus ( Trimerus ) harrisoni (McCoy, 1876). 7, holotype NMV P7503, complete exoskeleton, dorsal view x 1.8 (inter-

nal mould) from PL1620. 9, NMV P136645, complete exoskeleton, dorsal view of cephalon with impression of hypostome x 2.1 (internal mould)

from PL1620. 11, NMV P2500, complete exoskeleton, lateral view x 2.6 (internal mould) from PL1620.

Homalonotid trilobites from the Silurian and Lower Devonian

sub-ocular furrows, weak eye ridges. Preglabellar field 0.2

times cranidial length. Anterior branch of facial suture straight

poster-iorly, converging at about 55°, then anteriorly curving

strongly to the transverse, rostral suture transverse. Dorsal sur-

face of rostral plate semicircular, without connective sutures,

equal in length to preglabellar field. Ventral surface of rostral

plate with length equalling width, connective sutures moder-

ately convex and converging posteriorly at about 90°. Pygidium

triangular, short, length 0.6 times width, with sides weakly con-

vex and converging posteriorly at about 110° to an obtusely

pointed tip. Pygidial axis narrow, width (measured across sec-

ond ring) 0.3 times pygidial width, 10 axial rings, ring furrows

deep. 7-8 pleural ribs, pleural furrows as deep as ring furrows

and uniform in depth to lateral border furrow, rib-ring medial-

ly offset at fifth rib. Axial furrows moderately impressed poste-

riorly, poorly defined anteriorly, postaxial ridge posteriorly

raised. Lateral border furrow well defined, border a raised

ridge.

Discussion. The distinctive tricuspid cephalic margin immed-

iately distinguishes Trimerus ( Romiotis ) otisi from all other

members of the genus. The pygidium of otisi is also distin-

guishes the species from many congeners, with deep pleural

and ring furrows and the anteriorly indistinct axial furrow

shared only with the Bolivian T. (R.) sp. A. The Bolivian

species also displays a well defined border furrow and border

comparable to that of otisi and T. (R.) thomasi, but the species

differs in having longer pygidial proportions (L:W~0.9) and a

wider pygidial axis (width 0.5 pygidial width). The very short

pygidial proportions of otisi are closest to those of T. (R.) iani,

that also shares comparable cephalic features including moder-

ate length of the preglabellar field, longer glabellar proportions,

a glabellar outline weakly expanded across LI -LI (tr.), and a

forward eye position (opposite 0.5 cranidial length). In addition

to the tricuspid margin, otisi differs from iani in having distinct

subocular furrows and eye ridges.

The tricuspid cephalic margin of Trimerus ( Ramiotis ) otisi is

comparable to that of Digonus, as is the quadrate course of the

preocular facial sutures and the very weak expression of the

pygidial axial furrows anteriorly, with up to the third rib fused

with the axial rings. The species also resembles Digonus in the

very deep and equally deep pleural and ring furrows. The mod-

erately well defined glabellar lobation and glabellar outline

weakly expanded across LI -LI (tr.) are comparable to early

Digonus morphologies best represented by D. zeehanensis, and

in these respects otisi is the best candidate as an intermediate

species between Trimerus and Digonus. Significant features

precluding the assignment of otisi to Digonus include the lack

of a ventral process on the rostral plate, the very narrow pygidi-

al axis, and the strongly raised postaxial ridge. T. (R.) otisi and

Digonus further differ in the expression of the dorsal sections

of the connective sutures (short in Digonus but absent in otisi),

and in the size of the medial cephalic process (small in Digonus

but very large in otisi). In the large size of the medial cephalic

cusp, otisi is most closely comparable to T. (T.) johannis.

However, marked differences in cephalic morphology between

tricuspid T. {Trimerus) (represented by johannis), T. ( Ramiotis )

(represented by otisi) and Homalonotus suggest that the tri-

cuspid cephalic margin was independently derived in these

groups.

The paratype cephalon of Homalonotus vomer (NMV

P12303, Fig. 20.1 and figured Chapman, 1912, pi. 63 fig. 1,

Gill, 1949, text-fig. IB) belongs to Trimerus {Ramiotis) otisi,

and is designated a paratype of the new species. Chapman

(1912) considered the specimen to be a juvenile form of vomer,

but did not otherwise compare it with the holotype cephalon.

Although Chapman’s description of vomer seems to be based

entirely on the holotype, Gill (1949) included features of the

paratype in his redescription of the species. Chapman and Gill

recorded the localities of the paratype and the holotype of

vomer only as “Wandong”. The holotype was almost certainly

collected from PL286 (Williams locality F22, Wandong),

where the species occurs in relative abundance and in an

identical lithology to that of the holotype. As noted by Gill, the

paratype occurs in a yellow-brown, fine grained sandstone.

T. {R.) otisi has been collected from similar lithologies in the

Merriang Syncline to the east of Wandong, and it is presumed

the specimen was collected in that area, and probably in the

vicinity of PL300, Comet Creek Mine, Clonbinane.

It is remarkable that although Trimerus {Ramiotis) otisi is

very common in the Eden Park Form a tion in the Merriang

Syncline between Merriang and Clonbinane, trilobites (pre-

dominantly homalonotid) are exceedingly rare in the equivalent

horizons of the nearby Kinglake Basin sequence.

Figure 20. Trimerus {Ramiotis) otisi sp. nov. la, paratype NMV P12303 (and paratype of Homalonotus vomer Chapman, 1912), cephalon, dorsal

view x 1.9 (latex cast) from Wandong (exact locality unknown), lb, same, x 1.7 (internal mould). 2, paratype NMV P304726, cranidium, dorsal

view x 2.7 (latex cast) from PL6633. 3, paratype NMV P304739, incomplete cephalothorax, dorsal view x 3.2 (latex cast) from PL1898. 4,

paratype NMV P304797, incomplete cephalothorax, dorsal view of cephalon x 2.7 (internal mould) from PL 1898. 5a, holotype NMV P304741,

cephalon and displaced thoracopygon, dorsal view of cephalon x 1.15 (internal mould) from PL 1898. 5b, same, enlargement of anterior margin

x 2.3. 5c, same, anterior view of cephalon x 1.15. 6, paratype NMV P304727, cephalon and displaced thoracopygon, dorsal view of cephalon x

2.75 (internal mould) from PL6633. 7, paratype NMV P304723, cephalon, enlargement of anterior margin x 1.6 (internal mould) from PL6633.

8, paratype NMV P304722, cephalon, enlargement of anterior margin x 2.3 (latex cast) from PL6633. 9a, paratype NMV P304730, cephalon,

anterior view x 2.1 (latex cast) from PL6632. 9b, same, oblique view. 9c, same, dorsal view. 10, paratype NMV P304738, thoracopygon, dorsal

view x 3.0 (latex cast) from PL1 898. 11, paratype NMV P304734, cephalon, dorsal view x 4.3 (internal mould) from PL6632. 12, paratype NMV

P304733, cephalon, ventral view (doublure) x 2.0 (latex cast) from PL6632. 13, paratype NMV P304724, cephalon, ventral view (doublure) x 3.4

(latex cast) from PL6633. 14a, paratype NMV P304720, pygidium, lateral view x 1.9 (latex cast) from PL6633. 14b, same, dorsal view x 1.8. 15a,

paratype NMV P304719, pygidium, dorsal view x 1.15 (latex cast) from PL6633. 15b, same, lateral view. 16a, paratype NMV P304729,

pygidium, dorsal view x 1.7 (latex cast) from PL6632. 16b, same, posterior view x 1.6. 17, paratype NMV P304742, pygidium, dorsal view x 2.4

(internal mould) from PL 189 8. 18, paratype NMV P304737, pygidium, ventral view (doublure) x 1.45 (latex cast) from PL300. 19, paratype NMV

P304718, pygidium, dorsal view x 1.4 (internal mould) from PL6633.

Homalonotid trilobites from the Silurian and Lower Devonian

Environmental notes. See taphonomy and biofacies. Trimerus

( Ramiotis ) otisi is considered to have inhabited mid shelf

environments.

Trimerus ( Ramiotis ) thomasi sp. nov.

Figure 21

Trimerus ( Dipleura ?) sp.. — Talent, 1964: 49 (pars), fig. 6 non pi. 26

figs 1-2 ( =Digonus wenndorfi sp. nov.)

Type material. Holotype NMV P305067 (pygidium) from PL6653,

Heathcote, Victoria (Fig. 21.15). Paratypes NMV P305046-P305047

(cephala), NMV P305048, NMV P305053-P305056, NMV P305058,

P305059, (cranidia), NMV P305072-P305073 (librigena), NMV

P305061, NMV P3 04063, NMV P305068-P305070, (pygidia) from

PL2264, Thomas locality F45, Parish of Heathcote, Heathcote.

Paratype NMV P63385 (cranidium), NMV P305043 (pygidium) from

PL2265, Thomas locality F46, Parish of Heathcote, Heathcote. For

localities see Fig. 8.

Previously figured material. NMV P63385 (ex GSV38132, cranidium,

figured Talent, 1964: text-fig. 6) from PL2265.

Registered material. 94 specimens. 3 cephala, 40 cranidia, 5 librigenae,

1 thoracic segment, 45 pygidia. NMV P305042-P305045, NMV

P305 127-P305 130 from PL2265. NMV P305046-P305053, NMV

P305055-P305066, NMV P305068-P305123, NMV P305126 from

PL2264. NMV P305124-P305125, NMV P305054, NMV P305067

from PL6653. NMV P305131 from PL6654, Heathcote. NMV

P305132 from PL6655, Heathcote. NMV P305133 from PL6656,

Heathcote. Unregistered specimens from PL2234, Thomas locality

F21, Parish of Heathcote, Heathcote, PL6727, Thomas locality F28,

Parish of Redcastle, Heathcote. For localities see Fig. 8.

Stratigraphic distribution. Mclvor Formation, -500 m above the base

of the unit, lower Notoparmella plentiensis Assemblage Zone, mid

Ludlow.

Derivation of name. For Alan T. Thomas (University of

Birmingham), for his contribution to the study of homalonotids.

Diagnosis. Cephalon with length about 0.7 times width.

Glabella with length equalling width, trapezoid in outline, sides

more or less straight, tapering weakly forwards at about 25°.

Glabellar lobation distinct, SI -S3 very shallow, LI, L2, L3 and

frontal lobe subequal in length (exsag.). Anterior margin of

glabella well defined, transverse or with broad medial inden-

tation. Preglabellar field long, 0.25 times cranidial length,

slightly concave (tr. sect.). Palpebral lobe placed with midline

opposite 0.45 cranidial length (0.6 glabellar length) and with

8-6 1.6 times preoccipital glabellar width. Anterior margin of

cranidium transverse to very broadly convex. Pygidium with

length equal to width, sides converging at about 70°, angular

tip. Pygidial axis wide, 0.43 times pygidial width, continuous

with wide, raised postaxial area. 9 distinct axial rings, 7 distinct

pleural ribs, axial furrows shallow, pleural furrows moderately

impressed, rib-ring offset at fifth-sixth rib.

Remarks. Although specimens are abundant, the quality of the

material of Trimerus ( Ramiotis ) thomasi and its similarity to

T. (R.) otisi does not warrant a full description. The trapezoid,

straight-sided and moderately tapered glabellar outline indicate

assignment to Trimerus {Ramiotis). The moderate length of the

preglabellar field and the weak glabellar lobation are in accord

with this assignment. The cranidium figured by Talent (1964:

fig. 6) as T. (Dipleural) sp. is significantly larger than cranidia

from the type locality of T. (R.) thomasi which lies about 500m

south-east of PL2265 and more or less on strike. The larger

specimen differs conspicuously in that the anterior branches of

the facial sutures are more strongly convergent (-70°) and the

rostral suture correspondingly shorter (tr.), the preglabellar

field is slightly shorter (0.22 cranidial length), and the medial

flexure of the occipital furrow is strongly expressed (see Fig.

21.12). Whether these differences are attributable to the size or

to variability within the species cannot be resolved without

further specimens of large individuals. Within the range of

intraspecific variability, there are specimens of thomasi

exhibiting very weak lobation, and short and more strongly

tapered glabellar outlines (e.g. Figs 21.4, 21.5). These

morphs are closely comparable to the contemporary

T. (R.) salteri from England. Original illustrations of the holo-

type [Salter, 1865: pi. 12 fig. 1, as Homalonotus ( Koenegia )

ludensis ] indicates that the English species differs from thomasi

in having a wider (tr.) preocular fixigenal field and deeper axial

furrows.

Trimerus {Ramiotis) permutus from the upper Ludlow of

Poland is close in age to T. {R.) thomasi. In cephalic morph-

ology permutus differs markedly from thomasi in exhibiting

strong glabellar lobation, an elongate glabellar outline, more

strongly convergent facial sutures, and a short preglabellar

field. The species are more closely comparable on pygidial

features. Although pygidia of permutus are poorly known, they

share with thomasi the elongate pygidial proportions and mod-

erately and equally impressed axial, pleural and ring furrows.

Figure 21. Trimerus {Ramiotis) thomasi sp. nov. 1, paratype NMV P305046, cephalon, dorsal view x 2.5 (internal mould) from PL2264. 2,

paratype NMV P305048, cranidium, dorsal view x 2.5 (latex cast) from PL2264. 3, paratype NMV P305055, cranidium, dorsal view x 2.6 (inter-

nal mould) from PL2264. 4, paratype NMV P305059, cranidium, dorsal view x 2.4 (latex cast) from PL2264. 5, paratype NMV P305053,

cranidium, dorsal view x 2.7 (internal mould) from PL2264. 6, paratype NMV P305056, cranidium, dorsal view x 2.9 (latex cast) from PL2264.

7, paratype NMV P305054, cranidium, dorsal view x 2.6 (latex cast) from PL6653. 8, paratype NMV P305058, cranidium, dorsal view x 2.6 (latex

cast) from PL2264. 9a, paratype NMV P305047, cephalon, anterior view x 2.3 (latex cast) from PL2264. 9b, same, oblique view x 1.8. 9c, same,

dorsal view x 2.4. 10a, paratype NMV P305072, librigena, lateral view x 2.0 (internal mould) from PL2264. 10b, same, dorsal view (latex cast).

11, paratype NMV P305073, librigena, ventral view (doublure) x 1.7 (latex cast) from PL2264. 12, NMV P63385, cranidium, dorsal view x 1.95

(internal mould) from PL2265. 13a, paratype NMV P305068, pygidium, lateral view x 1.9 (internal mould) from PL2264. 13b, same, dorsal view.

14, paratype NMV P304063, pygidium, dorsal view x 3.0 (internal mould) from PL2264. 15a, holotype NMV P305067, pygidium, dorsal view

x 3.0 (internal mould) from PL6653. 15b, same, posterior view. 15c, same, oblique view. 16, paratype NMV P305070, pygidium, ventral view

x 4.0 (internal mould) from PL2264. 17, paratype NMV P305061, pygidium, dorsal view x 2.5 (latex cast) from PL2264. 18a, paratype NMV

P305043, pygidium, lateral view x 2.4 (latex cast) from PL2265. 18b, same, dorsal view x 2.5. 19, paratype NMV P305069, pygidium, lateral

view x 3.2 (internal mould) from PL2264.

Andrew C. Sandford

The pygidia differ in that thomasi exhibits a markedly raised

postaxial ridge, whilst that of permutus is low.

Trimerus ( Ramiotis ) otisi from southern central Victoria is

another contemporary of T. (R.) thomasi. Despite their geo-

graphic and temporal proximity, otisi and thomasi can be

easily distinguished. The pygidia of thomasi are much more

elongate, have a wider axis, and exhibit shallower pleural and

ring furrows and deeper axial furrows. The cranidia of thomasi

generally exhibit a more straight-sided and shorter glabellar

outline, more weakly defined glabellar lobation, and a longer

preglabellar field. Despite these differences, otisi and thomasi

are considered to be closely related. Together with the poorly

known T. ( R .) sp. A from Bolivia, the species share a distinct

pygidial morphology including pleural furrows that continue to

a deep border furrow, and a raised ridge-like border. This

pygidial morphology distinguishes this species group from

Llandovery-Wenlock T. {Ramiotis). In other respects T. (R.) sp.

A is morphologically intermediate between otisi and thomasi,

exhibiting longer pygidial proportions of the latter and deeper

pygidial pleural and ring furrows of the former.

Of the Llandovery-Wenlock species of Trimerus (Ramiotis),

T. (R.) thomasi shows greatest resemblance to T. (R.) tom-

czykowae from the Wenlock of Victoria (described below), that

also exhibits very weak lobation, a transverse rostral suture,

shorter glabellar proportions and a long preglabellar field. The

species also share moderate and subequal depth of the pygidial

pleural and ring furrows, distinguishing them from other

Llandovery-Wenlock T. (Ramiotis). T. (R.) tomcykowae differs

in having a short, rounded pygidial outline, slightly longer

glabellar proportion, and a deep medial indentation of the

glabellar anterior margin.

Environmental notes. Trimerus (Ramiotis) thomasi is the dom-

inant element of monospecific or low diversity assemblages.

Three cephala from PL2264 are the only known articulated

specimens, isolated tergites representing 97% of the entire

population, typical of taphofacies Til. The species occurs in

medium-grained sandstones, associated with a shelly fauna

dominated by gastropods and brachiopods. T. (R.) thomasi is

considered to have inhabited inner shelf environments.

Trimerus ( Ramiotis ) tomczykowae sp. nov.

Figures 19.5, 19.8, 19.10, 19.12

Type material. Holotype NMV PI 38203 (pygidium) from the “ Illaenus

band”, Costerfield, Victoria (Fig. 19.8). Paratype NMV P305191

(cranidium) from PL2263, Thomas locality F44, Parish of Dargile,

Costerfield. Paratypes NMV P138292, P138293 (rostral plates) from

PL1460, Thomas locality F43A, Parish of Dargile, Costerfield. For

localities see Fig. 10.

Registered material. 8 specimens: 1 cephalon, 3 cranidia, 2 rostral

plates, 2 pygidia. NMV P138291-P138294, NMV P138296, NMV

P139358 from PL1460. NMV P305191 from PL2263. NMV P138203

from the “ Illaenus band”.

Stratigraphic distribution. Illaenus band, Wapentake Formation.

Rickards and Sandford (1998) interpreted Ananaspis typhlagogus to

indicate a Wenlock age for these beds.

Derivation of name. For Ewa Tomczykowa (Instytut

Geologiczny, Poland) for her contribution to the study of

homalonotids.

Diagnosis. Glabella trapezoid, elongate, length ~1.1 times

width, sides parallel opposite paraglabellar area, straight and

converging at about 20° anteriorly, with extremely weak

lobation, anterior margin strongly indented. Paraglabellar area

distinct. Palpebral lobe placed at about 0.55 glabellar length.

Rostral suture more or less transverse. Dorsal surface of rostral

plate long, one third length of ventral surface, anterior margin

of rostral plate with sides converging at 115°, rounded medi-

ally. Connective sutures straight, diverging forwards at 55°.

Ventral surface of rostral plate flat, length equalling width.

Pygidial axial furrows moderately impressed. Axis about 0.4

times pygidial width, sides straight and tapering at 25°, poster-

ior third of axis moderately convex and raised, terminal piece

continuous with and not distinguishable from wide, raised,

subparallel- sided postaxial ridge. 10 axial rings, ring furrows

moderately impressed, 7 pleural ribs, pleural furrows moder-

ately impressed and equal in depth to ring furrows, shallowing

distally. Pleural offset at fourth rib.

Discussion. Trimerus (Ramiotis) tomczykowae is a very rare

element of the Illaenus band fauna. Despite the very few and

fragmentary specimens available, a fairly complete reconstruc-

tion of the cephalon can be made, and together with the single,

well-preserved pygidium clearly represents a new species of

homalonotid and a full description of the species is possible

with the material at hand. Significant cephalic characters

include the elongate, trapezoid, straight- sided, moderately

tapering glabella, the weakly expressed glabellar lobation, the

moderate length of the preglabellar field (0.25 cranidial length)

and the short pygidial proportions (LAV-0.9) indicate assign-

ment to T. (Ramiotis). In cephalic features tomczykowae differs

from the type species T. (R.) rickardsi in having a transverse

rostral suture and strong medial indentation of the anterior

glabellar margin. In these respects tomczykowae is closest to

T. (R.) dyaulax.

The equal depth of pleural and ring furrows attained by

Trimerus ( Ramiotis ) tomczykowae is considered here to repre-

sent a significant stage of homalonotine development. This

feature distinguishes Wenlock-Ludlow T. (Ramiotis) from

Llandovery members of the group. Although in its short

pygidial proportions and rounded outline the affinities of

tomczykowae to Llandovery T. (Ramiotis) are clear, it repre-

sents a transitional morphology between these and Upper

Silurian species of T. (Ramiotis) and T. (Trimerus).

Indeterminate homalonotids from the Wenlock of

central Victoria include a partly disarticulated exoskeleton from

the old Tooronga Brick Pit, high in the Anderson Creek

Formation, only briefly examined by the author. The abundant

and diverse trilobite fauna occurring in the Bylands Siltstone at

PL206, Wallan has yielded only an single homalonotid thoracic

segment.

Environmental notes. Trimerus (Ramiotis) tomczykowae is a

very rare element of a moderately diverse fauna occurring in

the nodular mudstones of the Illaenus band. The fauna is dom-

inated by the blind illaenid Thomastus thomastus Opik, 1953.

Homalonotid trilobites from the Silurian and Lower Devonian

Together with Ananaspis typhlagogus the composition of the

fauna closely resembles a contemporary fauna from Argentina

described by Waisfeld and Sanchez (1993). The taphonomy of

the Illaenus band is characterised by an abundance of complete

exoskeletons of Thomastus in the ‘bumastoid stance’, pre-

sumed to be individuals preserved in their infaunal life position

(Sandford and Holloway, 1998). The taphonomy and the aute-

cology of Thomastus in the mudstones suggest a deeper water

environment for tomczykowae. Several specimens of tom-

czykowae occur in a richly fossiliferous sandstone presumably

interbedded within the mudstone, although the bed is not

known in outcrop.

Wenndorfia gen. nov.

Type species. Homalonotus mutabilis Koch, 1880 from the Lower

Devonian (upper Emsian) of Germany.

Other species included. Parahomalonotus angustico status

Tomczykowa, 1975, P. bostoviensis Tomczykowa, 1975, Digonus ele-

gans Tomczykowa, 1975, Homalonotus expansus Hector, 1876 (=H.

( Burmeisteria ) huttoni Allan, 1935, -D. margaritifer Wenndorf, 1990),

H. forbesi Rouault, 1855, Dipleura fornix Haas, 1968, Trimerus lily-

dalensis Gill, 1949, H. miloni Renaud, 1942, H. multicostatus Koch,

1883a, H. mutabilis Koch, 1880, T. novus Tomczykowa, 1975, H.

obtusus Sandberger and Sandberger, 1849, P. planus junior Wenndorf,

1990, H. planus Sandberger, 1849, U P. sp. nov. A” in Wenndorf, 1990,

“D. sp.” in Le Menn et al., 1976.

Range. Lower Devonian (Lochkovian-Emsian).

Diagnosis. Glabella of moderate height to very low, weakly

tapering. Lobation indistinct. Anterior margin of cranidium

U-shaped and more or less concentric with rounded anterior

margin of glabella, anterior branches of facial suture broadly

curved and strongly convergent anteriorly, rostral suture short

(tr.), transverse or continuous in curvature with anterior section

of facial suture. Eyes placed posteriorly, opposite 0.3-0.45

cephalic length. Sides of glabella more or less straight and

parallel, varying to strongly concave. Ventral surface of rostral

plate with low or prominent anterior node. Pygidial outline

parabolic with rounded tip, but triangular with pointed tip in

early species. Pygidium with axial furrows very shallow to

indistinct, axis without independent convexity, wide (0.4-0.65

time pygidial width anteriorly), strongly tapering (furrows con-

verging at 30-45°), not reaching margin but terminating at

about 0.85-0.95 times pygidial length, semicircular terminal

piece short (sag.), slightly raised, but often indistinct from

postaxial field.

Discussion. Wenndorfia has been erected to accommodate

many species previously assigned to Parahomalonotus (see

above). In establishing Parahomalonotus, Reed (1918) listed a

number of characters in the diagnosis that are not apparent in

the type species Homalonotus gervillei DeVerneuil, 1850 from

the Emsian of France. Reed described the “facial sutures

uniting in a regular wide arched commissure close to (the)

anterior margin” as diagnostic of the genus (Reed, 1918: 326).

However, in gervillei the anterior cranidial margin is quadrate,

the rostral suture being transverse and the anterior branches of

the facial sutures subparallel (see Pillet, 1973: fig. 120). Reed’s

original diagnosis also states a pygidial entire margin and more

or less indistinct trilobation as diagnostic. However, in con-

tradiction to these definitive parameters, trilobation is well

defined by the raised pygidial axis of gervillei, and the pos-

taxial ridge extends posteriorly as a short posteromedial spine

(see Pillet, 1973, pi. 37 fig. 5).

The revised diagnosis for Parahomalonotus s.s. (see above)

emphasises the distinctive features of P. gervillei, and hence

differs markedly from that given by Reed (1918). Of species

assigned to Wenndorfia, Reed assigned Homalonotus planus,

H. obtusus and H. multicostatus to Parahomalonotus with

question. In the course of their facial sutures and in pygidial

features, these species are in closer agreement with Reed’s

diagnosis of Parahomalonotus than with the type gervillei.

These species further differ from gervillei in having pygidial

axes that are much wider anteriorly, taper more strongly, are not

independently convex, lack postaxial ridges, and terminate

between 0.85 and 0.95 pygidial length, and glabellae that are

very low and lack distinct lobation.

Species included in Wenndorfia were previously assigned

variously to Digonus, Dipleura, Parahomalonotus and

Trimerus. Wenndorfia is most reliably distinguished from these

genera by the rounded outline of the anterior cranidial margin,

concentric to the strongly rounded glabellar anterior margin.

This morphology contrasts most strongly with the angular,

quadrate anterior cranidial margin of Digonus. In pygidial

morphology early representatives of Wenndorfia and Digonus

are alike, although marked differences between these groups

are manifest in later representatives in trends toward short,

rounded outlines, and elongate, triangular outlines with acute

processes respectively. Later representatives of Wenndorfia

further differ from Digonus in exhibiting moderately to

strongly concave glabellar sides.

Rostral morphology is recognised in this work as a reliable

character distinguishing Wenndorfia from Trimerus and

Dipleura. The rostral plate of Wenndorfia exhibits a diamond-

shaped outline and exhibits a variably developed antero-

medial node, whereas rostral plates of Trimerus and

Dipleura are elongate pentangular and pentangular in outline

respectively, and lack rostral processes.

Developmental trends in the pygidial morphology of

Wenndorfia, manifest in the replacement of triangular outlines

by rounded outlines in the mid-Pragian, are comparable to

developmental trends in Dipleura in the Late Silurian.

However, pygidia of species assigned to Wenndorfia vary

markedly in the depth of the pleural and ring furrows. In a

number of species the pleural and ring furrows are very shallow

to indistinct, and approach morphologies exhibited by species

of Dipleura. The distinction of these morphologically conver-

gent species relies on the course of the cephalic sutures, as dis-

cussed above (see Dipleura ). Pygidia of Trimerus ( Ramiotis )

and T. ( Trimerus ) are distinguished from the Wenndorfia

pygidial morphology in having a distinct postaxial ridge.

Wenndorfia mutabilis, unlike most other species of the

genus, is abundant and its dorsal and ventral morphology is

both completely known and recently redescribed (see

Wenndorf, 1990). The species exhibits the rounded anterior

cranidial margin, the weakly expressed pygidial trilobation and

Andrew C. Sandford

the entire pygidial margin included in Reed’s original diag-

nosis of Parahomalonotus and in the diagnosis of Wenndorfia.

Other features exhibited by mutabilis and considered typical

of Wenndorfia include the strongly rounded anterior margin of

glabella, the posteriorly placed eyes, the small node on the

ventral surface of rostral plate, and the wide, strongly tapering

axis terminating at about 0.85 pygidial length. W. mutabilis is

distinguished from its congeners in having a glabella of moder-

ate height with strongly concave sides, a wide palebral area,

and a shorter pygidial outline with shallow pygidial ring and

pleural furrows.

Lochkovian-lower Pragian Wenndorfia differ from upper

Pragian-Eifelian species in variously exhibiting features that

can be regarded as underived. These features include a

trapezoid glabellar outline, the expression of glabellar lobation,

moderately impressed pygidial axial furrows, deep pleural and

ring furrows, and a triangular pygidial outline with an obtusely

angled tip. In these respects these early species represent a

transitional morphologies with early Digonus. Early represen-

tatives of Wenndorfia include several Polish homalonotids orig-

inally described as species of Digonus by Tomczykowa (1975)

and regarded by Wenndorf (1990) as representing an early

Digonus morphology. Lacking in these Polish species is the

quadrate anterior cranidial outline exhibited by the earliest

Digonus (see above, D. wenndorfi). The strongly rounded

anterior glabellar margin, the concentric cranidial margin and

posteriorly placed eyes indicate assignment of these species to

Wenndorfia. The upper Lochkovian W. bostoviensis from

Poland is the earliest species assigned to Wenndorfia.

W. bostoviensis differs from W. mutabilis and other Wenndorfia

in having and a short triangular pygidial outline. This pygidial

morphology suggests affinities of the earliest Wenndorfia to the

earliest Digonus.

Tomczkowa (1975) assigned homalonotids from upper

Lochkovian-lower Pragian strata immediately overlying

Wenndorfia bostoviensis to Digonus vialai. The number of

specimens representing these two morphologies is limited, with

four cranidia representing vialai and two representing

bostoviensis. Tomczkowa distinguished vialai from bostov-

iensis by its trapezoid rather than rectangular glabellar outline,

but the significance of these supposed differences cannot be

determined without reference to larger populations. In all other

respects it is difficult to distinguish vialai from bostoviensis,

and the specimens are best considered conspecific. Similarly,

Tomczykowa described Parahomalonotus angustico status

from the lower Pragian of Poland using a limited collection of

pygidia, only one complete. Tomczykowa (pi. 6 figs 1-4)

assigned pygidia from a slightly lower horizon to

Parahomalonotus forbesi (Rouault, 1855), distinguished from

those of angusticostatus in having fewer axial rings and ribs

and shallower pleural and ring furrows. However, the pygidia

figured do not differ markedly from angusticostatus and are

considered to be conspecific.

Wenndorfia expansa (Hector, 1876)

Figure 22.7-22.14

Homalonotus expansus Hector, 1876: 602, pi. 27 fig. 2.

Homalonotus sp. — Hutton, 1888: 257.

Homalonotus (Burmeisteria) huttoni. — Allan, 1935: 28, pi. 1 figs

4-5.

Homalonotus (Digonus) expansus. — Allan, 1935: 29, pi. 1 fig. 1.

Homalonotus ( Digonus ) cf. expansus. — Allan, 1935: 29, pi. 1 fig. 3.

Burmeisteria ( Digonus ) expansus. — Saul, 1965: 271.

Burmeisteria huttoni. — Saul, 1965: 271. — Tomczykowa, 1975: 11.

Digonus expansus. — Tomczykowa, 1975: 11. — Wenndorf, 1990:

16.

Burmeisteria ( Digonus ) cf. expansus. — Speden and Keyes, 1981:

pi. 4 fig. I.

Burmeisteria expansa. — Cooper, 1982: 27.

Burmeisteria huttoni. — Cooper, 1982: 27. — Wenndorf, 1990: 16.

Digonus margaritifer — Wenndorf, 1990: 77, pi. 11 figs 8-9.

Type material. Homalonotus expansus. Lectotype (pygidium, figured

Hector, 1876, Allan, 1935: pi. 1 fig. 1, Fig. 22.10 herein, in the

Geological Survey of New Zealand, cast in Museum Victoria regis-

tered NMV PI 6844) from McKay locality 129, Rainy Creek, Reefton,

south island, New Zealand. Paralectotype (pygidium, also the holotype

of Digonus margaritifer, figured Allan, 1935: pi. 1 fig. 3, Wenndorf,

1990: pi. 11 fig. 8, in the Geological Survey of New Zealand, cast in

Museum Victoria registered NMV PI 6846) from McKay locality 130,

LankeyGully, Reefton. Paralectotype (pygidium, figured Hector, 1876,

in the Geological Survey of New Zealand, cast in Museum Victoria

registered NMV P16847) from locality 129.

Homalonotus (Burmeisteria) huttoni. Holotype ZFc33 (dorsal

exoskeleton, figured Allan, 1935: pi. 1 figs 4, 5) from “near Reefton”.

Allan (1935) suggested the specimen is from locality 129.

Figure 22. 1-22.6. Digonus wenndorfi sp. nov. 1, paratype NMV P304713, cranidium, dorsal view x 1.4 (internal mould) from PL2203. 2, paratype

NMV P304862, pygidium, dorsal view x 1.5 (internal mould) from PL2203. 3a, paratype NMV P304864, pygidium, posterior view x 1.35

(internal mould) from PL2203. 3b, same, lateral view x 1.25. 4, paratype NMV P304866, pygidium, dorsal view x 1.25 (internal mould) from

PL2203. 5, paratype NMV P304710, cranidium, dorsal view x 1.0 (internal mould) from PL2203. 6, paratype NMV P304717, pygidium,

posterior view x 1.15 (internal mould) from PL2203.

Figure 22.7-22.14. Wenndorfia expansa (Hector, 1876). 7a, holotype of Homalonotus ( Burmeisteria ) huttoni Allan, 1935, ZFc 33, enrolled

exoskeleton, dorsal view of pygidium x 0.7 (internal mould) from near Reefton (exact locality unknown). 7b, same, lateral view of enrolled

exoskeleton. 7c, same, dorsal view of cephalon. 7d, same, posterior view of enrolled exoskeleton. 8a, NMV P64122, pygidium, dorsal view x 0.9

(internal mould) from “Reefton”. 8b, same, posterior view. 9, paralectotype of Homalonotus expansus Hector, 1876 and holotype of Digonus

margaritifer, pygidium, dorsal view x 0.9 (internal mould) from locality 130, Reefton (NMV P16846, plastercast of original). 10a, lectotype of

Homalonotus expansus Hector, 1876, pygidium, dorsal view x 1.15 (internal mould) from locality 129, Reefton (NMV P16844, plastercast of

original). 10b, same, external mould. 11, paralectotype of Homalonotus expansus Hector, 1876, pygidium, dorsal view x 0.7 (internal mould) from

locality 129, Reefton (NMV P16847, plastercast of original). 12, NMV P64121, pygidium, dorsal view x 1.23 (internal mould) from “Reefton”.

13, NMV P64120, pygidium, dorsal view x 0.95 (internal mould) from “Reefton”. 14, ZFc 58, incomplete thoracopygon, dorsal view x 0.75

(internal mould) from “Reefton”.

Andrew C. Sandford

Digonus margaritifer. Holotype (pygidium, and paralectotype of

Homalonotus expansus , see above). Paratype (pygidium, figured

Wenndorf, 1990: pi. 11 fig. 9, in the Palaontologisches Museum der

Humboldt-Universitat Berlin, Germany), documented as coming from

Kilmore, Victoria, acquired through the fossil dealer Kranz in 1885.

However as the paratype is undoubtedly conspecific with the New

Zealand material, as no homalonotids other than Trimerus ( Trimerus )

vomer , Trimerus ( Ramiotis ) otisi and Dipleura garratti are yet known

in the well-collected Wenlock-Ludlow trilobite faunas from the

Kilmore area, and as Wenndorfia would be most unexpected in strata

of this age, I conclude that the Berlin specimen is from the Reefton

area and its documentation confused, possibly by Kranz, with a

specimen of T. (T.) vomer. Kranz may have acquired the Berlin

specimen from Theodore Ranft who was the first to collect fossils in

Lankey Gully at Reefton in 1872. Part of Ranft’s collection was

purchased by the Melbourne Museum, who also had dealings with

Kranz.

Previously figured material. NZGS AR 676 (thoracopygon, figured

Speden and Keyes, 1981: pi. 4 fig. I) from locality GS3737, S38/f523,

Rainy Creek, Reefton.

Registered material. 12 specimens: 1 complete exoskeleton, 2 thora-

copygons, 1 incomplete thorax, 8 pygidia,. NMV PI 6844, NMV

P16847 from locality 129. P16846 from locality 130. NZGS AR676

from locality GS3737. NMV P64120-P64122 from Lankey Gully

(Ranft collection). ZFc33, ZFc58, ZFc309, ZFc350 from “Reefton”.

One pygidium in the Palaontologisches Museum der Humboldt-

Universitat Berlin.

Stratigraphic distribution. Lankey Limestone, IBoucotia loyolensis

Assemblage Zone, Emsian.

Diagnosis. Glabella extremely low, sides parallel, without dis-

tinct lobation, anterior margin broadly rounded, length 1.1

times width. Palpebral lobes placed opposite -0.55 glabellar

length. Axial furrows very poorly defined. Pygidium short,

with length 0.7 times width, weakly concave sides, converging

posteriorly at about 100° to an obtusely angular tip. Pygidial

axis wide, about 0.4 times pygidial width and very poorly

defined anteriorly, tapering moderately with sides straight and

converging at about 30°, length about 0.85 times pygidial

length, posterior margin parabolic, 12-13 rings, semicircular

terminal piece with distinct posterior margin. Axial furrows

poorly defined, indicated by flexure of pleurae, almost indis-

tinct anteriorly. 9 pleural ribs. Pleural furrows not reaching

margin. Pleural and ring furrows deep and of equal depth.

Anteriorly ribs and rings continuous, pleural offset at seventh

rib. Row of equidimensional, regularly spaced tubercles on

axial area of thoracic and pygidial segments, with two or three

supplementary rows of smaller tubercles. Tubercles large on

larger specimens, small to fine on smaller specimens. Similar,

but less regular tuberculation on posterior border of fixigenae

and thoracic and pygidial pleurae. Genal field with densely

spaced, coarse granules.

Discussion. Three homalonotids have been named from the

Lower Devonian at Reefton. The best known of these is

Homalonotus ( Burmeisteria ) huttoni, based on a single, near-

complete, enrolled exoskeleton (Fig. 22.7). The specimen was

described in detail in open nomenclature by Hutton (1888), and

later named by Allan (1935). Several points in Hutton’s

original description of the specimen cannot be substantiated, in

particular those concerning the cephalic shape and proportions,

and the presence of distinct glabellar lobation. Although only

the first six segments of the pygidium are preserved in the holo-

type, the ornament of tubercles on the pleural ribs and axial

rings are distinctive and shared by several more completely

preserved pygidia in the Museum of Victoria (NMV P64 120-2,

Figs 22.8, 22.12-22.13) and in the New Zealand Geological

Survey (NZGS AR 676, Fig. 22.14). These pygidia also share

very deep ring and pleural furrows that are continuous to the

seventh segment. The axial furrow is not impressed on the

anterior half of the pygidium, but its position is indicated by a

posteriorly increasing flexure at the junction of the ring

and pleural furrows. These specimens are considered to be

conspecific with the holotype of huttoni.

The other two species, Homalonotus expansus and Digonus

margaritifer, were based only on pygidia. Wenndorf ’s (1990)

description of margaritifer includes features identical with

those of H. (. Burmeisteria ) huttoni, such as the ornament, the

deep axial ring and pleural furrows continuous to the seventh

rib, the very shallow axial furrows, and the wide rounded-

triangular outline. Wenndorf noted expansus and margaritifer

shared pleural offsetting at the seventh-eighth rib, but distin-

guished the former by the smooth surface texture (absence of

tubercules) and the weak definition of the axis of the former

species. Close inspection of the external mould of the lectotype

of expansus reveals, however, a row of small tubercles on the

first four axial rings and pleurae (see Fig. 22.10b).

Corresponding ornament on the anteriormost rings on the

internal mould were not recorded either by Hector (1876) or by

Allan (1935) as this area of the pygidium is damaged. The

spacing of these tubercles on the lectotype is similar to that of

huttoni. The differences in the coarseness of tuberculation

between the type specimens of expansus and specimens of

huttoni are attributed here to the size of the pygidia. The

lectotype of expansus, with the finest tubercles, is the smallest

specimen. Moderately sized specimens including the

holotype of margaritifer have slightly larger tubercles (see Fig.

22.9), whereas the largest of specimens including the

holotype of huttoni have much larger tubercles. This interpreta-

tion is in accord with Cooper’s (1982) suggestion that

expansus and huttoni might be synonyms. The differences in

definition of the axis between margaritifer and expansus

noted by Wenndorf (1990) can be attributed to the flattening

of the lectotype of expansus, axial convexity obscured by

crushing and longti-tudinal folding of the tergite. Taking this

deformation into account, whatever differences may have

existed between the specimens do not appear to be significant.

In the absence of significant differences in ornament

or other features between the types of expansus and pygidia

of margaritifer and huttoni, the species are regarded as

conspecific.

There is little to support the assignment of Homalonotus

expansus to Burmeisteria. The most reliable character of

Burmeisteria recognised in this work is the exceptionally high

number of pygidial segments, with B. herschelii having up to

17 axial rings and 11 pleural furrows. H. expansus has only 12

axial rings and 9 pleural ribs. Reed (1918) emphasised the

biconcave course of the rostral suture in herschelii as a generic

Homalonotid trilobites from the Silurian and Lower Devonian

character. Cooper (1982) suggested the course of the rostral

suture of herschelii to be variable and probably ontogenetic-

ally related, supporting earlier doubts on its significance

(Sdzuy, 1957, Saul, 1965). Notwithstanding this debate, the

anterior portion of the cephalon (and the rostral suture) of the

holotype of huttoni is not preserved. B. herschelii is strongly

polymorphic, with variable glabellar morphology, but the

glabella of expansus differs in having no trace of lobation or

spines, and in that the axial furrows are subparallel and much

shallower. In the absence of rostral morphology, the assignment

of huttoni to Burmeisteria by various workers (Allan, 1935,

Wenndorf, 1990) was presumably based on the similarity of

the tuberculate ornament to that of herschelii. The arrange-

ment of these tubercles suggests, however, they are not homo-

logous, but independently derived. As noted by Cooper (1982),

the tubercules of herschelii are arranged longitudinally. This

arrangement differs from the transversely arranged tubercles on

expansus.

Tuberculation similar to that exhibited by Homalonotus

expansus is known amongst members of Digonus. Wenndorf

(1990) noted a close similarity in pygidial ornament between

the paratypes of margaritifer and the ornatus group. Wenndorf

added that margaritifer shared few other ornatus- group

characters. The narrow pygidial axis is incompatible with

assignment of expans a to Digonus.

Generic assignment of Homalonotus expansus to

Wenndorfia emphasises its low glabellar height, rounded anter-

ior glabellar margin, posteriorly placed eyes, indistinct

pygidial axial furrows and narrow axial width, and the contin-

uity of the ring and pleural furrows, the termination of the axis

at about 0.9 pygidial length, and the absence of a postaxial

ridge. Its relationships to other species of Wenndorfia are diffi-

cult to assess, but it differs from all other species in exhibiting

a coarsely tuberculate thoracic and pygidial ornament. In over-

all appearance, pygidia assigned to W. expansa most closely

resemble the deeply furrowed pygidia of W. multicostata. The

triangular pygidial outline, however, distinguishes it from

multicostata and most other Wenndorfia, as discussed above.

As the cephalic morphology of multicostata is poorly known, it

is difficult to make a detailed comparison with expansa. The very

low height and poor definition of the glabella of expansa is

approached only by W. plana plana, although the latter differs

in that the glabellar axial furrows are quite distinct posteriorly.

Shirley (1938) recorded Homalonotus sp. from the Baton

Formation at Baton River, east of Nelson, North Island, New

Zealand. He considered ten crushed and deformed pygidia to be

identical with pygidia of Wenndorfia expansa. Shirley’s

description of the number of axial rings and pleural ribs and the

continuity of the rings and pleurae are in accord with expansa,

but as I have not examined these specimens I can make no

judgement on their affinities. The Baton Formation is gener-

ally considered younger than the Lankey Limestone at Reefton,

although its age is variably cited as Pragian (Boucot et al.,

1969) or Lochkovian (Wright, 1990).

The newly documented material warrants a revised diagno-

sis of the species, but otherwise is too limited to warrant a com-

plete description to replace those of Hutton (1888), Allan

(1935) and Wenndorf (1990).

Figure 23. Geological sketch map of the Lily dale area showing

Lochkovian-basal Pragian fossil localities yielding homalonotids. For

other fossil localities see also Gill (1940, fig. 1, 1945, fig. 2), Moore

(1965, fig.l), VandenBerg (1970), Garratt (1972), Wall et al. (1995,

fig. 1), Sandford (2003, text-fig. 1A, 2004, fig. 1).

Andrew C. Sandford

Environmental notes. The taphonomy of the population of

Wenndorfia expansa (as a whole) are attributable to Speyer and

Brett’s taphofacies 4B, with Ar=33% and the relative

abundance of completely enrolled specimens (8%). W. expansa

is interpreted to inhabit deep, outer-shelf environments. This

suggested habitat is comparable to the deepest water facies

associated with populations of many other species of

Wenndorfia (see Wenndorf, 1990)

Wenndorfia lilydalensis (Gill, 1949)

Figures 5C, 24

Homalonotus harrisoni. — Cresswell, 1894: 156.

Homalonotus sp. — Chapman, 1907: 239. — Gill, 1938: 170.

Trimerus lilydalensis Gill, 1949: 69, pi. 8 figs 4-5, pi. 9 fig. 7,

text-fig. IF — Holloway and Neil, 1982: 145.

Type material. Holotype NMV P14587 (cephalon, figured Gill, 1949:

pi. 8 figs 4-5, text-fig. IF, Fig. 24.1 herein, counterpart previously

registered NMV P14588) from PL1801, Gill locality 1, Mooroolbark,

Victoria. Paratype NMV PI 45 89 (pygidium, figured Gill, 1949: pi. 9

fig. 7) from PL1801. For locality see Fig. 23.

Registered material. 57 specimens: 1 articulated dorsal exoskeleton, 1

disarticulated dorsal exoskeleton, 1 enrolled cephalothorax, 9 cephala,

7 cranidia, 3 librigenae, 12 thoracic segments, 23 pygidia. NMV

P304527 from PL1805, Gill locality 5, Coldstream, Victoria. NMV

P304531, P304532 from PL1990, Coldstream. NMV P304528-

P304530 from PL1813, Gill locality 13, Mooroolbark. NMV

P304524-P304526 from PL 1887, Gill locality 87, Mooroolbark. NMV

P3204533, NMV P304570 from PL1869, Gill locality 69,

Mooroolbark. NMV P304549-P304558 from PL1801. NMV P304567,

P304569 from PL6661, Lilydale, Victoria. NMV P457, NMV

P304559-P304562 from PL1802, Gill locality 2, Lilydale. NMV

P3045 1 6-P3045 1 8 from PL1810, Gill locality 10, Lilydale. NMV

P304522 from PL1858, Gill locality 58, Lilydale. NMV P304534-

P304548, NMV P304566 from PL1859, Gill locality 59, Lilydale.

NMV P304523 from PL 1862, Gill locality 62, Lilydale. NMV

P304520, P304521 from PL 1829, Gill locality 29, Kilsyth, Victoria.

NMV P304563-P304565 from “Lilydale”. NMV P304519 from “with-

in 1 km of Mooroolbark Railway Station”. NMV P304571 probably

from the Lilydale area. For localities see Fig. 23.

Stratigraphic distribution. Humevale Siltstone, from 1750 m above the

base of the unit up to a horizon 3700 m above the base of the unit,

upper Boucotia australis Assemblage Zone to lower Boucotia

loy-olensis Assemblage Zone, late Lochkovian-earliest Pragian.

Diagnosis. Cephalon weakly pentangular in outline, with

length 0.56 times width. Glabellar length equalling width, sides

straight, weakly tapering (15°), strongly rounded anteriorly.

Glabellar lobation weakly defined. Palpebral lobe placed with

midline opposite 0.5 cranidial length. Preglabellar field

(excluding rostral plate) 0.15 times cranidial length. Anterior

cranidial margin evenly rounded, concentric with glabellar

anterior margin. Dorsal surface of rostral plate crescentic in

shape, length (sag.) 0.05 times cephalic length, anterior margin

obtusely angular (130°). Ventral surface of rostral plate wide,

kite-shaped, width 1.15 times length. Pygidium triangular,

length 0.8 times width, tip obtusely pointed (-100°). Axis very

wide anteriorly, width 0.66 times pygidial width, length 0.92

times pygidial length, sides straight. 9-11 axial rings, 8 pleural

ribs, ring and pleural furrows deep. Surface of cephalon with

fine tubercles, more distinct and densely distributed adjacent to

the cephalic margin.

Description. Exoskeleton with maximum size moderate (estimated 20

cm from NMV P304562).

Cephalon with pentangular outline, sides converging forwards at

70-75° opposite glabella and at about 135° opposite preglabellar field,

length about 0.57 times width. Glabella with length 0.75 times

cephalic length, width 0.45 times cephalic width, sides converging at

13-17°, length ranging between 1.06-0.91 times width. Occipital ring

length 0.1 times cranidial length, slightly wider medially. Occipital

furrow deep on internal moulds, shallow on external moulds, weak

forward flexure medially. Glabellar anterior margin well defined, with

arc of curvature centred at 0.55 times glabellar length. Glabella weak-

ly convex (tr., sag.). Glabellar lobation very weakly defined (best seen

on NMV P304562 and NMV P304516, Figs 24.2, 24.4), LI 0.22 times

glabellar length, L2 and L3 0.11 times glabellar length. S3 transverse,

S2 directed inwards-backwards at about 7° from the transverse and S 1

at 15° from the transverse. Axial furrows wide, shallow posteriorly,

moderately impressed anteriorly, paraglabellar areas poorly defined.

Preglabellar field of uniform width, flat. Length (exsag.) of posterior

border equal to occipital length abaxially, lengthening adaxially to 2.0

times occipital length. Posterior border furrow transverse, shallow and

very wide, meeting lateral border furrow distally. Postocular fixigenal

area short, length (exsag.) 0. 14 times cranidial length. Palpebral lobe

0.13 times cranidial 1.75 times preoccipital glabellar width, very

shallow 6-6 length, palpebral furrow. Preocular fixigena area wide,

0.22 narrowing forwards anteriorly. Anterior branches of facial suture

broadly curved, meeting connective sutures almost at margin opposite

0.9 cephalic length. Librigena with wide, moderately impressed

border furrow, librigenal area weakly convex, steeply inclined, lateral

border wide and convex, shallow, wide subocular furrow. Dorsal

surface of rostral plate slightly inclined (in lateral view, see Figs 24.2c,

24.3c), length (exsag.) 0.18 times width (tr.). Ventral surface of rostral

plate kite-shaped, with slightly medial flexure (tr.) giving anterior

Figure 24. Wenndorfia lilydalensis (Gill, 1949). la, holotype NMV P14587, cephalon, dorsal view x 2.3 (latex cast) from PL1801. lb, same,

oblique view x 2.5. lc, same, dorsal view x 1.8 (internal mould). 2a, NMV P304516, cephalon and displaced thoracopygon, dorsal view, enlarge-

ment of anterior margin of cephalon x 5.0 (latex cast) from PL1810. 2b, same, dorsal view of cephalon x 1.5 (internal mould). 2c, same, oblique

view of cephalon x 1.4 (latex cast). 2d, same, dorsal view of thoracopygon x 1.3 (latex cast). 3a, NMV P304536, cephalon, ventral view (dou-

blure) x 2.2 (latex cast) from PL1859. 3b, same, dorsal view x 2.25. 3c, same, lateral view x 2.55. 4, NMV P304562, cephalon, dorsal view x 2.2

(internal mould) from PL1802. 5, NMV P304531, cephalon, ventral view (doublure) x 3.3 (latex cast) from PL1990. 6, NMV P304528, cephalon,

dorsal view x 1.3 (latex cast) from PL1813. 7, NMV P304550, pygidium, dorsal view x 1.4 (internal mould) from PL1801. 8a, NMV P304565,

pygidium, posterior view x 2.9 (latex cast) from “Lilydale” 8b, same, dorsal view. 8c, same, lateral view. 9, NMV P304534, pygidium, dorsal

view x 2.2 (internal mould) from PL1859. 10, paratype NMV P14589, pygidium, dorsal view x 2.1 (internal mould) from PL1801. 11a, NMV

P304549, pygidium, lateral view x 1.6 (internal mould) from PL1801. lib, same, dorsal view (latex cast). 12, NMV P304566, pygidium, ventral

view (doublure) x 2.8 (internal mould) from PL1859. 13, NMV P457, pygidium, dorsal view x 1.5 (internal mould) from PL1802. 14, NMV

P304550, pygidium, dorsoposterior view x 1.7 (internal mould) from PL 1801.

Homalonotid trilobites from the Silurian and Lower Devonian

Andrew C. Sandford

margin of cephalon a very weak M-shaped outline, flat posteriorly.

Connective sutures weakly sinusoidal, diverging at 90° posteriorly and

at 50° anteriorly. Posteriorly, connective sutures are either confluent

immediately anterior to the meeting the hypostomal suture (NMV

P304536, Fig. 24.3a), or meet the hypostomal suture separately (NMV

P304531, Fig. 24.5).

Thorax with 13 segments. On external moulds axial furrows and the

pleural flexure are not defined, although the axis is marked on internal

moulds by exsagittal line of deep depressions (axial articulating

processes) on the posterior margin of each segment. Pleural furrows

wide and deep, pleural tips rounded.

Pygidium with sides weakly and uniformly convex. Axial furrows

converging at about 45°, indistinct opposite first and second rings,

shallow posteriorly. Axis poorly defined posteriorly without postaxial

ridge. Pleural furrows not reaching margin, border poorly defined and

lacking independent convexity from pleural field, without border

furrow. In posterior view anterior margin strongly convex, posterior

margin weakly arched to accommodate rostral flexure. In lateral view

dorsal margin steep (-45°) and gently curved, ventral margin more or

less horizontal.

Discussion. Trimerus lilydalensis exhibits several features

indicative of assignment to Wenndorfia, including the strongly

rounded anterior glabellar margin and the concentric anterior

cranidial margin, the antero-medial rostral node, the weak

pygidial trilobation, and the termination of the pygidial axis at

about 0.9 pygidial length. The species was originally described

from a limited number of poorly preserved specimens, but is

redescribed from a much larger population.

Gill’s (1949) description of the species includes several of

the diagnostic characters listed above, although the revised

diagnosis differs in a number of points. Gill described the

cephalon as being markedly inflated (it is only moderately

convex, see Fig. 24.2c), and the exoskeleton as being smooth

(it bears fine tubercules and pits, see Fig. 24.2a).

Holloway and Neil (1982) considered specimens of Digonus

wenndorfi from the Heathcote area to be possibly conspecific

with Wenndorfia lilydalensis. W. lilydalensis can be easily

distinguished from wenndorfi in having pygidia lacking a

raised postaxial ridge, and cranidia with a U-shaped rather than

quadrate anterior margin, a more weakly tapered glabella with

a more rounded anterior margin, and a forwardly convex rather

than transverse rostral suture.

Wenndorfia lilydalensis is most closely comparable to the

contemporary W. bostoviensis from the upper Lochkovian of

Poland. The species share a similar trapezoid, moderately

tapering, straight-sided glabellar outline and a very wide (tr.)

palpebral area. Glabellar lobation is variably expressed in

lilydalensis, and although Tomczykowa (1975) noted an

absence of glabellar lobation for bostoviensis, shallow SI -S3

can be seen on specimens considered here to be con-

specific with bostoviensis (see discussion above). More

significantly, bostoviensis also exhibits a relatively underived

pygidium, with a triangular pygidial outline with an acutely

angled tip. Pygidial axial furrows are moderately impressed

on bostoviensis, distinguishing it from lilydalensis and younger

species of Wenndorfia, that share very shallow to effaced

pygidial axial furrows. The only other Wenndorfia to exhibit a

triangular pygidial outline is the lower Pragian Polish W. nova,

with less elongate pygidial proportions and a very narrow

pygidial axis. In cranidial morphology nova shows some

resemblance to lilydalensis, although the former differs in

having narrow palpebral areas.

Wenndorfia lilydalensis is confined to the Lilydale

sequence. One specimen labelled as coming from the Seville

area, collected by F. Chapman, was found to have a counterpart

labelled as coming from the Lilydale area, collected by

J. Jutson. The lithology of the specimen matches lithologies

from the Lilydale sequence rather than those from Seville.

Gill’s (1938) record of the species from PL 1835, Gill locality

35, Seville is also probably erroneous, as the lithology of the

specimen is unlike that at PL1835, but again closely matches

lithologies of the Lilydale sequence.

Environmental notes. The faunal associations of Wenndorfia

lilydalensis are complex. W. lilydalensis first appears as a rare

element in the trilobite fauna (relative abundance 2%), but

through its range steadily increases in relative abundance,

reaching maximum relative abundance in the upper horizons of

its range. In the lower part of its range lilydalensis frequently

occurs in phacopid-dominated assemblages, but in the upper

parts of its range lilydalensis is frequently part of a distinct

acastid/homalonotid dominated association

With the exception of a complete exoskeleton from a bio-

clastic coquinal sandstone at PL 1805 (taphofacies Till), all

specimens of Wenndorfia lilydalensis are found in a siltstone

lithology preserved as isolated sclerites or partly disarticulated

specimens including cephala, a cephalon with 7 thoracic

segments, and a moult assemblage, being a cephalon lying

obliquely over the thorax. A cranidium and nearby pygidium on

the same bedding plane might also be interpreted as a moult

assemblage (taphofacies TIV). An outer shelf setting is sug-

gested as the preferred environment of W. lilydalensis, which

ranges only as a rare faunal element to mid shelf settings and to

even deeper settings where it occurs with a calymenid-

phacopid association. The taphonomy of the latter, with a high

degree of articulation and containing sparsely distributed moult

assemblages and rare enrolled specimens represents a new

taphofacies for central Victoria, designated taphofacies TV,

equivalent to Speyer and Brett’s (1986) taphofacies 4B (see

Fig. 6).

Acknowledgements

I extend my sincere thanks to Dr Alan Thomas (University of

Birmingham) and to an anonymous referee for their most

detailed and helpful reviews of the manuscript, and for alerting

me to a number of publications on British homalonotids which

I had overlooked. Research for this work was funded from an

Australian Postgraduate Award. I gratefully acknowledge Dr

David Holloway (Museum Victoria), Dr Malcolm Wallace

(University of Melbourne) and Dr Stephen Gallagher

(University of Melbourne) for their supervision of this project.

Mr Peter Duncan (Eden Park) kindly donated specimens of

Trimerus ( Ramiotis ) otisi collected from his property. I also

thank Dr Norton Hiller, Canterbury Museum, Christchurch,

New Zealand for the loan of specimens of Wenndorfia expansa

including the holotype of Homalonotus ( Burmeisteria ) huttonv.

Homalonotid trilobites from the Silurian and Lower Devonian

and Mr Robert Jones at the Australian Museum for the loan of

a well-preserved cranidium of Trimerus ( Trimerus ) harrisoni ,

regretfully lost.

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Memoirs of Museum Victoria 62(1): 67-89 (2005)

ISSN 1447-2546 (Print) 1447-2554 (On-line)

http://www.museum.vic.gov.au/memoirs/index.asp

Pliocene marine mammals from the Whalers Bluff Formation of Portland,

Victoria, Australia

Erich M.G. Fitzgerald

School of Geosciences, Monash University, Vic. 3800, Australia and Museum Victoria, G.P.O. Box 666, Melbourne, Vic.

3001, Australia (efitzger@museum.vic.gov.au)

Abstract Fitzgerald, E.M.G. Pliocene marine m a mmals from the Whalers Bluff Formation of Portland, Victoria, Australia.

Memoirs of Museum Victoria 62(1): 67-89.

The most diverse and locally abundant Australian fossil marine mammal assemblages are those from late Neogene (Late

Miocene through Late Pliocene) sediments in Victoria and Flinders Island, Tasmania. However, none of these

assemblages have hitherto been described. The Pliocene (>2.5^1. 8 Ma) Whalers Bluff Formation, exposed in beach cliff

sections and offshore reefs, at Portland, western Victoria (38°19'S, 141°38'E) has yielded a small but moderately

diverse assemblage of marine mammals represented by fragmentary material. Taxa present include: right whales

(Balaenidae); rorqual whales (Balaenopteridae); a physeterid similar to the extant sperm whale (cf. Physeter sp.); the first

Australian fossil record of pygmy sperm whales (Kogiidae); at least three genera of dolphins (Delphinidae: cf. Tursiops

sp., Delphinus sp. or Stenella sp., and an undetermined genus and species); and probable earless or tme seals (Phocidae).

This small assemblage represents the first Australian fossil marine mammal assemblage to be described in detail. The

taxonomic composition of this Pliocene marine mammal assemblage is generally similar to the present day marine

mammal assemblage in north-west Bass Strait. The occurrence of extant cetacean genera in the Portland Pliocene and

Blinders Island Cameron Inlet Formation assemblages indicates that the marine m a mmal fauna off south-east Australia

had acquired an essentially modern aspect by the Late Pliocene. Several of the cetacean genera recorded in the Portland

Pliocene assemblage also occur in similar-aged assemblages in other ocean basins. This corroborates the hypothesis that

many cetacean taxa that are widely distributed in the world’s oceans today were equally widespread during the Pliocene.

Keywords Cetacea, Carnivora, Pinnipedia, Phocidae, Mysticeti, Odontoceti, Australia, Victoria, Portland, Whalers Bluff Formation,

Pliocene

Introduction

The Pliocene epoch (1.8-5. 3 Ma) is generally considered to be

the time during which the modem marine mammal fauna

evolved, with the extinction of archaic taxa (as well as some

taxa with novel adaptations), and widespread geographic

distribution of extant families and genera (Bames, 1977;

Fordyce, 1989; Fordyce and Barnes, 1994; Fordyce and

Muizon, 2001; Fordyce et al., 2002; Demere et al., 2003).

Although the Pliocene marine mammals of the North Pacific

(e.g. Barnes, 1973a, 1977, 1998) and eastern tropical

Pacific (e.g. Muizon, 1981, 1984; Muizon and DeVries, 1985;

Muizon and Domning, 1985, 2002) have been described and

discussed in some detail, the Pliocene marine mammals of

the Southwest Pacific (Australia and New Zealand) remain

poorly known (Fordyce et al., 2002: 53). This is despite the fact

that Australian late Neogene marine mammals (mostly

cetaceans) are relatively abundant in museum collections,

especially the Palaeontology Collections of Museum Victoria,

Melbourne.

The majority of Pliocene marine mammal fossils in these

collections are rather fragmentary with one partially complete

skull and associated skeleton known (NMV PI 79005, cf.

Megaptera sp.). Despite this general lack of diagnostic skull

material, some details of the SW Pacific Pliocene marine

mammal fauna may be filled in by the study of certain isolated

skeletal elements such as periotics. As noted by Bames (1977:

322), study of these isolated elements may provide data on the

taxonomic diversity within an assemblage and wider fauna.

Pliocene marine mammal assemblages have hitherto not been

described from Australia, so descriptions of even fragmentary

material provide an initial basis for understanding marine

mammal evolution off southern Australia during the Pliocene.

This description of marine mammals from the Pliocene Whalers

Bluff Formation assemblage comprises a preliminary basis for

the late Neogene fossil record of marine mammals in Australia.

Erich M.G. Fitzgerald

Figure 1. Locality of Portland in Victoria, south-east Australia, and the Portland fossil marine vertebrate localities. Fossils have been collected as

float along the beach and from adjacent cliffs between Dutton Way and Portland Harbour. Black shading indicates areas of cliff outcrop of the

Whalers Bluff Formation.

Pliocene marine mammals

All fossils were collected from coastal exposures of the

Whalers Bluff Formation lining Portland Bay in western

coastal Victoria, southeast Australia (38°19'S, 141°38'E)

(Fig. 1). Unfortunately, details of the geological context of vir-

tually all fossils are unknown apart from whether the fossils

were collected from the Whalers Bluff Formation or underlying

limestone. Fitzgerald (2004a, 2004b) mentioned the Portland

fossil marine mammals in previous publications. Bearlin (1987:

177) briefly noted the occurrence of cf. Balaena sp., and cf.

Balaenoptera sp. in private collections in an unpublished Ph.D.

thesis. The vertebrate faunal list for Portland given by

Fitzgerald (2004b: 186) was completed prior to the recognition

of two distinct, stratigraphically/temporally disjunct marine

vertebrate assemblages at Portland. The majority of the verte-

brates listed by Fitzgerald (2004b) were derived from the

Pliocene Whalers Bluff Formation although some vertebrates

from the Portland Late Miocene assemblage were listed under

the Whalers Bluff Formation assemblage. The Portland Late

Miocene marine vertebrate assemblage, from the Port

Campbell Limestone, is considerably more diverse than the

Pliocene Whalers Bluff Formation assemblage, and is to be

described in a subsequent publication. Below is an emended list

of the vertebrates recorded in the assemblage from the Whalers

Bluff Formation at Portland.

Chondrichthyes

Isurus sp.

Carcharodon carcharias Linnaeus, 1758

Carcharodon megalodon Agassiz, 1835

Myliobatis sp.

Ischyodus dolloi Leriche, 1902

Mammalia

Marsupialia

?Dasyuromorphia incertae sedis

Diprotodontoidea gen. et sp. undet.

Diprotodontoidea gen. et sp. undet. C

Diprotodontidae gen. et sp. undet. A

Zygomaturinae gen. et sp. undet. T

Palorchestes sp.

Vombatidae gen. et sp. undet.

Sthenurus sp.

Protemnodon sp.

Macropus sp.

Macropodidae gen. et sp. undet. C

Ektopodontidae gen. et sp. undet.

Rodentia

Rodentia incertae sedis

Carnivora

?Phocidae gen. et sp. indet.

Cetacea

Balaenidae gen. et sp. indet.

Balaenopteridae gen. et sp. indet.

cf. Physeter sp.

Kogiidae gen. et sp. indet.

Delphinoidea incertae sedis

cf. Tursiops sp.

Delphinus sp. or Stenella sp.

Delphinidae gen. et sp. undet. A

Materials and methods

All fossil specimens were collected by Mr Sean Wright of Portland and

are in the Palaeontology Collections of Museum Victoria. Anatomical

terminology for periotic s and tympanies follows Evans (1993),

Fordyce (1994), Fordyce and others (2002) and Kasuya (1973) with

mi nor modifications. All periotic and tympanic measurements follow

the methods and dimensions outlined by Kasuya (1973) and were made

using vernier callipers. Photographs were taken using a 35 mm Nikon

Nikkormat EL SLR with a 105 mm macro-lens, and a Nikon D70

digital SLR with a 60 mm macro-lens. Where indicated, specimens

were coated with a sublimate of ammonium chloride to enhance

contrast in black and white (denoted by AC in figure captions). Where

necessary, fragile specimens were consolidated with a hardener con-

sisting of 3% solution of Paraloid B72 (ethyl methacrylate/methyl

acrylate copolymer) in acetone.

Institutional abbreviations. NMV C, Museum Victoria Comparative

Anatomy Collection, Melbourne; NMV P, Museum Victoria

Palaeontology Collection, Melbourne; CD, Phylum Chordata cata-

logue, New Zealand Geological Survey, Lower Hutt; USNM, National

Museum of Natural History (formerly United States National

Museum), Smithsonian Institution, Washington, DC. For a complete

list of specimens referred to in this study, see table 1.

Geology and age of the Whalers Bluff Formation

For about 4 km along cliffs north of Portland Harbour the

Pliocene Whalers Bluff Formation is exposed (Singleton et al.,

1976). This formation is about 7.6 m thick, being comprised of

horizontally bedded fossiliferous clay, oyster-rich beds and

sandy limestones (Abele et al., 1988). These sediments uncon-

formably overlie the Upper Miocene Port Campbell Limestone

and infill a karst topography developed in the top of the

Miocene limestone (Boutakoff and Sprigg, 1953; Dickinson et

al., 2002). The Whalers Bluff Formation is unconformably

capped by basalts.

The age of the Whalers Bluff Formation is well constrained

relative to some other Neogene marine mammal-bearing units

in the SW Pacific (Fig. 2). However, the determination of the

younger age limit of the Whalers Bluff Formation has proved

problematic. The Port Campbell Limestone which underlies the

Whalers Bluff Formation is Late Miocene (indicated by pres-

ence of Globorotalia miotumida\ planktonic foraminiferal

zones N16-basal N17; Tortonian; 8-10.8 Ma) (Dickinson et al.,

2002). Deposition of the Whalers Bluff Formation began

during planktonic foraminiferal zone N19 (indicated by the

presence of Globorotalia puncticulata at the base of the for-

mation) and ensued into the base of planktonic foraminiferal

zone N21 (Fig. 2) (Singleton et al., 1976; Dickinson et al.,

2002). K-Ar dates of 2.5 1 Ma from basalts that cap the Whalers

Bluff Formation have been reported (Singleton et al., 1976).

Beu and Darragh (2001) have suggested that the Whalers

Bluff Formation is latest Pliocene to earliest Pleistocene

(>1.5-2.0 Ma) based on the presence of the pectinid bivalve

Pecten fumatus Reeve, 1852 in a section along the Glenelg

River. However, Pecten fumatus does not occur in the Whalers

Bluff Formation at Portland (Darragh in Singleton et al., 1976;

T.A. Darragh, pers. comm.). Zenatiopsis ultima Darragh and

Kendrick, 1971 occurs in the Whalers Bluff Formation at

Portland but is a Pliocene species and never occurs with

Erich M.G. Fitzgerald

Table 1. Specimens referred to in this study. For more detailed locality/stratigraphic data see Fitzgerald (2004b). Abbreviations: e=Early;

m=Middle; l=Late; M=Miocene; P=Pliocene; Pt=Pleistocene; R=Recent; Vic. = Victoria; Tas. = Tasmania; NZ = New Zealand.

Specimen

Taxon

Locality

Lormation

Age

NMV P221242

hums sp.

Portland, Vic.

Whalers Bluff

NMV P218415

Carcharodon megalodon

Portland, Vic.

Whalers Bluff

NMV P218418

Carcharodon carcharias

Portland, Vic.

Whalers Bluff

NMV P218470

Myliobatis sp.

Portland, Vic.

Whalers Bluff

NMV P2 18296

Ischyodus dolloi

Portland, Vic.

Whalers Bluff

NMV P221241

?Dasyuromorphia gen. et sp. undet.

Portland, Vic.

Whalers Bluff

NMV P2 18500

Diprotodontoidea gen. et sp. undet.

Portland, Vic.

Whalers Bluff

NMV P2 18498

Diprotodontoidea gen. et sp. undet. C

Portland, Vic.

Whalers Bluff

NMV P21 8499

Diprotodontidae gen. et sp. undet. A

Portland, Vic.

Whalers Bluff

NMV P221230

Zygomaturinae gen. et sp. undet. T

Portland, Vic.

Whalers Bluff

NMV P22 1231

Palorchestes sp.

Portland, Vic.

Whalers Bluff

NMV P221238

Vombatidae gen. et sp. undet.

Portland, Vic.

Whalers Bluff

NMV P221232

Protemnodon sp.

Portland, Vic.

Whalers Bluff

NMV P221235

Macropus sp.

Portland, Vic.

Whalers Bluff

NMV P221227

IMacropus sp.

Portland, Vic.

Whalers Bluff

NMV P221237

Sthenurus sp.

Portland, Vic.

Whalers Bluff

NMV P221229

Macropodidae gen. et sp. undet. C

Portland, Vic.

Whalers Bluff

NMV P197795

Ektopodontidae gen. et sp. undet.

Portland, Vic.

Whalers Bluff

NMV P221240

Rodentia indet.

Portland, Vic.

Whalers Bluff

NMV P2 18273

?Phocidae gen. et sp. indet.

Portland, Vic.

Whalers Bluff

NMV P21 8465

?Phocidae gen. et sp. indet.

Portland, Vic.

Whalers Bluff

NMV P2 18269

Balaenidae gen. et sp. indet.

Portland, Vic.

Whalers Bluff

NMV P2 18268

Balaenopteridae gen. et sp. indet.

Portland, Vic.

Whalers Bluff

NMV P2 18298

cf. Physeter sp.

Portland, Vic.

Whalers Bluff

NMV P21 8407

Kogiidae gen. et sp. indet.

Portland, Vic.

Whalers Bluff

NMV P21 8283

Delphinoidea incertae sedis

Portland, Vic.

Whalers Bluff

NMV P2 18284

Delphinoidea incertae sedis

Portland, Vic.

Whalers Bluff

NMV P2 18286

Delphinoidea incertae sedis

Portland, Vic.

Whalers Bluff

NMV P2 18266

cf. Tursiops sp.

Portland, Vic.

Whalers Bluff

NMV P2 18265

Delphinus or Stenella sp.

Portland, Vic.

Whalers Bluff

NMV P218264

Delphinidae gen. et sp. undet. A

Portland, Vic.

Whalers Bluff

NMV P16198

?Phocidae gen. et sp. indet.

Beaumaris, Vic.

Black Rock Sandstone

lM-eP

NMV P41759

Phocidae gen. et sp. indet.

Beaumaris, Vic.

Black Rock Sandstone

lM-eP

NMV P42523

?Phocidae gen. et sp. indet.

Beaumaris, Vic.

Black Rock Sandstone

NMV PI 60399

Phocidae gen. et sp. undet.

Beaumaris, Vic.

Black Rock Sandstone

NMV PI 60433

Phocidae gen. et sp. undet.

Beaumaris, Vic.

Black Rock Sandstone

NMV PI 60441

Phocidae gen. et sp. undet.

Grange Burn, Vic.

Grange Bum

NMV P215759

?Phocidae gen. et sp. indet.

Beaumaris, Vic.

Black Rock Sandstone

NMV P16195

Balaenidae gen. et sp. indet.

Beaumaris, Vic.

Black Rock Sandstone

NMV P48865

Balaenidae gen. et sp. indet.

Grange Burn, Vic.

Grange Bum

NMV PI 6043 8

Balaenidae gen. et sp. indet.

Beaumaris, Vic.

Black Rock Sandstone

lM-eP

NMV PI 97824

Balaenidae gen. et sp. indet.

Beaumaris, Vic.

Black Rock Sandstone

lM-eP

NMV P171503

Balaenoptera edeni or B. brydei

Tidal River, Vic.

N/A

NMV P179005

Megaptera sp.

Lakes Entrance, Vic.

Jemmys Point

NMV P23961

IMesoplodon sp.

Cameron Inlet, Tas.

Cameron Inlet

NMV P13033

“Stem” cudmorei

Beaumaris, Vic.

Black Rock Sandstone

lM-eP

NMV P204352

Delphinidae gen. et sp. undet. A

Henley, England

Red Crag

P-Pt

NMV P2 18481

Delphinidae gen. et sp. undet. A

Henley, England

Red Crag

P-Pt

NMV C24972

Kogia breviceps

Cape Conran, Vic.

N/A

NMV C24976

Kogia breviceps

Shelley Beach, Vic.

N/A

NMV C27879

Eubalaena australis

Altona Bay, Vic.

N/A

NMV C28892

Megaptera novaeangliae

Venus Bay, Vic.

N/A

CD 53

Delphinidae gen. et sp. undet. A

Chatham Island, NZ

Unnamed

USNM 22953

Orycterocetus crocodilinus

Calvert County, USA

Calvert

USNM 183007

Physeteridae gen. et sp. undet.

Lee Creek Mine, USA

Yorktown

USNM 452993

Scaphokogia cochlearis

Aguada de Lomas, Peru

Pisco

USNM 183008

Kogiidae gen. et sp. undet.

Lee Creek Mine, USA

Yorktown

USNM 251118

Kogiidae gen. et sp. undet.

Lee Creek Mine, USA

Yorktown

Pliocene marine mammals

Figure 2. Stratigraphic correlation of the Portland fossil marine mammal-bearing formations with selected major late Neogene marine mammal-

bearing units. Stratigraphy and geochronology are from Bames (1973, 1977, 1984, 1998), Muizon and DeVries (1985), Muizon and Bellon (1986),

Gottfried et al. (1994), Whitmore (1994), Prothero (1998), Fordyce (2002a), Fordyce et al. (2002), Fitzgerald (2004b), Muizon et al. (2004),

Bames et al. (2005) and Gradstein et al. (2004). Abbreviations: AGL, Pisco Formation, Aguada de Lomas level; BL, Batesford Limestone; BRS,

Black Rock Sandstone; CLB, Pisco Formation, Cerro la Bruja; ELJ, Pisco Formation, El Jahuay level; GBF, Grange Bum Formation; LAF,

Lower Member, Almejas Formation; MTM, Pisco Formation, Montemar level; SAO, Pisco Formation, Sacaco level; SAS, Pisco Formation, Sud-

Sacaco level; SDF, San Diego Formation; UAF, Upper Member, Almejas Formation; WBF, Whalers Bluff Formation.

P. fumatus, the latter first appearing at the base of the

Pleistocene (T.A. Darragh, pers. comm.).

These data indicate that the Whalers Bluff Formation at

Portland is Early to Late Pliocene (Zanclean to Piacenzian;

>2.5-4. 8 Ma). Further study of terrestrial mammals from the

Whalers Bluff Formation may help refine the geological age of

this unit. Unfortunately, the exact bed from which fossil verte-

brates were collected within the Whalers Bluff Formation is

unknown. Thus, a finer age resolution than that given above for

the assemblage is currently unavailable. The age range of the

Whalers Bluff Formation presented herein is considered to

be the best estimate based on available data and the reader must

be cautioned that future work may yield a younger limit on the

minimum age.

The Whalers Bluff Formation (as well as, in part, laterally

equivalent Victorian marine mammal-bearing units such as the

Grange Burn Formation, Black Rock Sandstone and Jemmys

Point Formation) has been interpreted as representing a

prograding quartz-carbonate barrier system with the elastic-

dominated units listed above representing an initial marine

incursion (Dickinson et al., 2002: 290).

Systematics of marine mammals

Order Cetacea Brisson, 1762

Suborder Mysticeti Flower, 1864

Family Balaenidae Gray, 1821

Genus and species indeterminate

Referred specimen. NMV P2 18269, incomplete right periotic; anterior

and superior processes virtually complete, but pars cochlearis almost

entirely worn off, and only anteriormost base of posterior process

preserved (Fig. 3A).

Description. P2 18269 is highly polished and abraded. The

anterior process is blunt and globose, being indistinct from the

superior process. There is marked lateral exostosis of the super-

ior process lateral to the epitympanic recess. The lateral aspect

of the anterior process is rugose and pitted. Posteriorly, this pit-

ting decreases in density. Only the lateralmost region of the

pars cochlearis is preserved. In medial view, the most notable

feature is the sulcus for the facial nerve (cr. VII), the course of

cr. VII being preserved from its entry into the body of the

periotic at the aperure of the internal facial foramen, to its

ventral exit into the epitympanic cavity via the ventral facial

foramen. All other features of the pars cochlearis and epitym-

panic recess have been obliterated. Posterior to the broad and

shallow hiatus epitympanicus is a remnant of the base of the

posterior process (which is directed posterolaterally and

somewhat ventrally).

Discussion. Miller (1924: 8-9) listed the following features that

distinguish the periotics of Balaenidae from those of

Balaenopteridae (and other baleen-bearing Mysticeti): (1) axis

of anterior process of periotic parallel with axis of internal

acoustic meatus; (2) [longitudinal] axes of anterior and posteri-

or processes converge at an acute angle; and (3) pars cochlearis

small relative to rest of periotic. In addition to the preceding

features, the possession of massive lateral exostosis of the

anterior process and anterolateral superior process, such that

the anterior process appears swollen (as noted by Fordyce,

1982: 48), seems to be a feature shared by all extant and late

Neogene balaenid periotics. It is largely on the basis of the

latter character and the phenetic similarity of P2 18269 to a

periotic (PI 6 195) from the Lower Pliocene Black Rock

Sandstone of Beaumaris identified as belonging to cf.

“ Balaena ” (Gill, 1957) that P2 18269 is referred to Balaenidae,

genus and species indeterminate.

Erich M.G. Fitzgerald

The fossil record of Balaenidae begins in the Late Oligocene

(c. 28 Ma: Fordyce, 2002b), although the record only becomes

reasonably well known from the Mio-Pliocene boundary

onwards (McLeod et al., 1993; Bisconti, 2003). Morenocetus

parvus Cabrera, 1926 is the geologically oldest named

balaenid, from the early Early Miocene (Aquitanian) of

Patagonia. From the end Aquitanian to early Tortonian of the

Miocene the evolutionary history of Balaenidae is virtually

unknown. The extant balaenids include Balaena mysticetus

Linnaeus, 1758, Eubalaena australis Desmoulins, 1822,

E. glacialis Muller, 1776, and E. japonica Lacepede, 1818

(e.g., Cummings, 1985; Reeves and Leatherwood, 1985;

Bannister, 2002). Note that Rice (1998) included all extant

balaenids in the genus Balaena and recognised only two

species, B. mysticetus and B. glacialis. The taxonomic scheme

of Bannister (2002) is used herein. Balaena is known from the

Early Pliocene of the North Atlantic (McLeod et al., 1993;

Westgate and Whitmore, 2002). There are very few confirmed

pre-Quatemary fossil records of Eubalaena. Bisconti (2003,

2005) referred the Pliocene Balaena belgica Abel, 1941 to

Eubalaena belgica. McLeod and others (1993: 63) suggested

that a balaenid periotic from the Early Pliocene of South

Australia (originally recorded by Howchin: 1919) could repre-

sent Eubalaena (as opposed to its original referral to Balaena).

Dixon (1990) described an incomplete Recent Eubalaena

australis skeleton from Altona Bay, near Melbourne, Victoria.

The latter specimen (C27879) includes tympanies and perio-

tics. The extinct genera Balaenula and Balaenotus have been

recorded from the Late Miocene through Pliocene of the N

Pacific (Barnes, 1977; McLeod et al., 1993) and N Atlantic

(McLeod et al., 1993; Bisconti, 2003 and references therein).

Recently, Bisconti (2005) described a new genus and species of

relatively small balaenid, Balaenella brachyrhynus, from the

Early Pliocene of Belgium.

The incompleteness of P2 18269 and lack of information on

the extent of intraspecific and ontogenetic variation in balaenid

periotics, hampers comparisons with described extant and

fossil balaenid taxa. Furthermore, there are as yet no published

criteria for discriminating between the periotics of Balaena and

Eubalaena. Despite these problems, it may be noted that

P2 18269 is similar in overall size to several isolated balaenid

periotics from the uppermost Miocene to Lower Pliocene Black

Rock Sandstone and Grange Burn Formation of Victoria (e.g.

P16195, P48865, P160438, and P197824). The discovery of a

more complete periotic (including the pars cochlearis) is neces-

sary before any further comparisons between the Portland

Pliocene balaenid and the other Victorian specimens listed

above can be made.

Family Balaenopteridae Gray, 1864

Genus and species indeterminate

Referred specimen. NMV P2 18268, incomplete right periotic; lacking

medial three-quarters of pars cochlearis and posterior process

(Fig. 3B).

Description. P2 18268 is polished, rolled and may be secondar-

ily phosphatised. The anterior process is elongated and some-

what attenuated anteriorly. The dorsal surface of the anterior

process is smooth, with only slight rugosity, as seen in the

periotics of extant Balaenopteridae. An oblique groove on the

dorsolateral surface of the anterior process near its preserved

apex is interpreted as a trace of a vascular sulcus. The latter

feature has previously been considered a sulcus for the cap-

suloparietal emissary vein (Geisler and Luo, 1998; Geisler and

Sanders, 2003) or as a sulcus marking the path of an artery,

specifically part of the middle meningeal artery (Fordyce,

1994). Fordyce (1994) and Watson and Fordyce (1994)

described this feature as the anteroextemal sulcus whereas

Geisler and Sanders (2003) treated the anteroextemal sulcus

and sulcus for the capsuloparietal emissary vein as separate fea-

tures. Further work is required to better establish the

venous/arterial correlate of this osteological feature which in

this study is referred to as the sulcus for the capsuloparietal

emissary vein. In extant balaenopterids, this sulcus usually

courses posteriorly to a point level with the position of the

mallear fossa. However, in P2 18268 any more posterior con-

tinuation of the sulcus for the capsuloparietal emissary vein, if

formerly present, no longer occurs due to abrasion.

The ventral presentation of the periotic exhibits several

features. As occurs in extant Balaenoptera and Megaptera, the

lateralmost eminence of the ventrolateral ridge of the superior

process (sensu Geisler and Luo, 1996) is situated at the same

level as the anterior margin of the pars cochlearis. The mallear

fossa is poorly differentiated from the rest of the epitympanic

recess.

The preserved posterolateral margin of the periotic is

formed by the hiatus epitympanicus. The course of the facial

nerve on the ventral surface of the periotic is marked by the

facial sulcus which is bounded anteriorly by the aperture of the

ventral facial foramen. In ventral view, a distinct bridge of

bone at the anterolateral comer of the preserved pars cochlearis

represents the ventral roof of the ventral facial foramen. The

endocranial aspect of the pars cochlearis preserves the aperture

of the internal facial foramen. Anterior to this aperture is a deep

excavation in the medial surface of the periotic at the base of

the anterior process. This region (composed of cancellous bone

in extant balaenopterids) marks the site of ankylosis between

the anterior process and the body of the periotic. As in other

Balaenopteridae, the pars cochlearis appears to have been

elongated towards the cranial cavity.

Discussion. That P2 18268 is a balaenopterid periotic is evident

by the possession of: (1) elongated, triangular and anteriorly

attenuated anterior process; (2) a triangular lateral eminence of

the ventrolateral ridge; and (3) a relatively large pars cochlearis

elongated towards the cranial cavity. Because P2 18268 is rep-

resented only by an incomplete periotic, it is not possible for it

to be identified below family level. The size of P2 18268 is

comparable to that of periotics of subadult Balaenoptera edeni

Anderson, 1879 or B. brydei Olsen, 1913 (P171503) and juve-

nile Megaptera novaeangliae Borowski, 1781 (C28892).

However, the periotics of extant Megaptera novaeangliae and

an undescribed species of Megaptera from the Early Pliocene

of Victoria (PI 79005) possess the following features which

differentiate them from P2 18268: (1) the anterior process is

Pliocene marine mammals

Figure 3. Mysticeti and Physeteridae from the Pliocene Whalers Bluff Formation, Portland. A, Balaenidae gen. et sp. indet., incomplete right peri-

otic, NMV P2 18269, in ventrolateral view (AC); B, Balaenopteridae gen. et sp. indet., incomplete right periotic, NMV P2 18268, in ventral view

(AC); C, cf. Physeter sp., apical crown of tooth, NMV P218298, in side view (AC). Scale bars equal 10 mm.

Erich M.G. Fitzgerald

relatively shorter; (2) anterior process is more dorsoventrally

compressed; (3) in endocranial view, there is an anteroposter-

iorly thickened region of cancellous bone in the pars cochlearis

anterior to the internal facial foramen; and (4) no deep excava-

tion in the endocranial surface of the periotic anterior to the

pars cochlearis. Many of these features may be related to onto-

genetic variation. At least, the lack of these four features in

P2 18268 may indicate that this periotic is not referrable to

Megaptera and may belong to an indeterminate species in the

genus Balaenoptera.

Suborder Odontoceti Flower, 1867

Family Physeteridae Gray, 1821

cf. Physeter sp. Linnaeus, 1758

Referred specimen. NMY P2 18298, isolated, worn-down apical

region of tooth crown (Fig. 3C).

Description. P2 18298 has an ovoid cross-section at its base

which becomes more ellipsoid towards the preserved apex of

the crown. In occlusal view, the apex of the tooth crown is

incised by a deep anteroposterior cleft which is attributed to

tooth wear. Shallow longitudinal grooves in the surface occur

on all faces of the crown. The basal end of the tooth is broken

to reveal a cross-section through the crown. The only notable

feature of this aspect of the tooth is the presence of thick layers

of cementum.

Discussion. The large size of this tooth and the thick layers

of cementum suggest that P2 18298 represents a physeterid.

Little more can be said about the systematic s of this speci-

men although its size and similarity to teeth of large adult

Physeter macrocephalus suggest affinities with the extant

sperm whale.

Family Kogiidae Gill, 1871

Genus and species indeterminate

Referred specimen. NMV P218407, incomplete left tympanic bulla

(Fig. 4A-B).

Description. The most striking aspect of the morphology of

P2 18407 is its small size. The tympanic is polished with rolled

edges being rounded off. The preserved portion includes only

the medial half of the bulla with very little of the outer lip pres-

ent. The base of the posterior process of the tympanic has been

worn off. In dorsal and ventral view, there is a distinct furrow

in the medial edge of the involucrum between the inner poster-

ior prominence and the inner anterior prominence. In ventral

view, the furrow between the prominences of the involucrum

forms an obtuse angle. There is no preserved ventral keel and

the median furrow is very shallow such that it is poorly differ-

entiated from the surrounding ventral surface of the tympanic.

The interprominential notch is relatively broad. The anterior

edge of the involucrum and outer lip is squared-off. In dor-

sal view, the involucrum has a consistent width along its

length, but is expanded at the level of the inner posterior

prominence.

Discussion. P2 18407 is referred to the Kogiidae on the basis of

the following features shared with extant and fossil kogiids: (1)

small overall size [as Kasuya (1973: 25) noted among extant

Odontoceti only Pontoporia blainvillei Gervais and d’Orbigny,

1844 has a smaller tympanic, and P2 18407 does not resemble

the tympanic of that taxon]; (2) distinct embayment in

the medial edge of the involucrum between the inner anterior

and posterior prominences; and (3) squared-off anterior edge

of the involucrum and outer lip. It should be noted that the

second feature is also seen in the tympanic bullae of

Physeter macrocephalus Linnaeus, 1758, Orycterocetus croco-

dilinus Cope, 1868 (USNM 22953) (Kellogg, 1965)

(Fig. 5C-D), and an Early Pliocene physeterid (USNM

183007) (Fig. 5A, B). Despite this similarity between P2 18407

and the tympanies of Physeteridae, the relatively large size of

physeterid tympanies precludes P2 18407 from being con-

sidered as a physeterid. Furthermore, the inner posterior

prominence in physeterid tympanies is generally more pointed

in outline than the rounded outer posterior prominences in

kogiid tympanies.

Among fossil Kogiidae, the tympanies of Praekogia

cedrosensis (Barnes, 1973b) have not been described. A skull of

Scaphokogia cochlearis Muizon, 1988 (USNM 452993)

includes an associated incomplete left tympanic (Fig. 4E, F).

The tympanic of S. cochlearis is similar to the tympanies of

extant Kogia in its relatively small size and possession of a dis-

tinct embayment in the medial side of the involucrum between

the inner anterior and posterior prominences. The most notable

difference between the tympanic of S. cochlearis and the

Portland kogiid tympanic lies in the more marked inflation of

the inner posterior prominence of P2 18407. S. cochlearis pos-

sesses a less expanded inner posterior prominence, such that

the embayment in the medial face of the involucrum is not as

deep as in P2 18407. In this respect, Scaphokogia cochlearis is

similar to two undescribed Early Pliocene kogiids from the Lee

Creek Mine, North Carolina (USNM 183008, Fig. 4G-H;

USNM 251118, Fig. 4C, D) and the extant Kogia breviceps

Blainville, 1838 (Fig. 41, J).

The features which Kasuya (1973) used to differentiate

between Recent Kogia breviceps and K. sima Owen, 1866 are

not preserved in P2 18407. However, comparison between fig-

ures of the tympanic of K. sima (Kasuya, 1973: plate VIII), and

actual specimens of K. breviceps (C24972, C24976), indicate

that P2 18407 differs from both extant Kogia species in: (1)

embayment in medial edge of involucrum between the inner

prominences is markedly deeper; and (2) the involucrum is less

dorsoventrally and mediolaterally inflated. Despite these dif-

ferences, P2 18407 is almost identical in size to the tympanies

of Kogia breviceps. Given that the currently available evidence

is meagre, P2 18407 is not identified below family level. Table

2 compares some dimensions of the tympanies of kogiids and

physeterids discussed above.

P2 18407 is the first fossil record of Kogiidae from

Australia. Fossil kogiids have previously been reported in the

SW Pacific region, from the ?Late Miocene of the Chatham

Rise, east of New Zealand (Fordyce, 1984a) but that record has

a poorly constrained age (Fordyce, 1989, 1991b).

Pliocene marine mammals

Table 2. Measurements of tympanies of Physeteridae and Kogiidae. Measurements follow methodology of Kasuya (1973). All measurements are

in mm.

NMV

C24972

NMV

P2 18407

USNM

22953

USNM

183007

USNM

452993

USNM

183008

USNM

251118

Standard length of tympanic bulla, distance from

anterior tip to posterior end of outer posterior

prominence

26.0

31.0

29.0

Distance from anterior tip to posterior end of inner

posterior prominence

19.9

21.6

27.0

31.0

Distance from posteroventral tip of outer posterior

prominence to tip of sigmoid process

21.28

Distance from posteroventral tip of outer posterior

prominence to tip of conical process

15.3

Width of tympanic bulla at the level of the sigmoid

process

26.0

Height of tympanic bulla, from tip of sigmoid process

to ventral keel

26.5

Width across inner and outer posterior prominences

19.0

20.2

22.5

20+

Superfamily Delphinoidea Gray, 1821

Incertae sedis

Referred specimens. NMV P218283, P218284 and P218286, all isolat-

ed teeth (not figured).

Description. P21283, P218284 and P218286 all represent small

odontocete teeth possessing conical enamel-covered crowns

that bear fine wrinkling ornamentation, and curve lingually

towards the crown apex. As in kentriodontids, there is a lingual

bulge at the base of the crown but this feature is not as promi-

nent in the teeth from Portland. None possesses an open pulp

cavity suggesting that all were derived from adult individuals.

P2 18283 is an incomplete tooth, its preserved maximum

length and maximum width of the crown being 16 mm and 6

mm respectively. Due to the incomplete nature of this tooth it

does not warrant further description.

P2 18284 is the most highly polished and the most complete.

It differs from the others in having a mediolaterally compressed

root with a more prominent mesial-distal bulge at its midpoint.

The preserved apex of the root curves posteriorly.

The most notable feature of P2 18286 distinguishing it from

the other teeth is its bulbous root, which contrasts with the

transversely flattened morphology of P2 18284.

Discussion. Only one delphinoid odontocete has previously

been described from the Tertiary of Australia, the latest

Miocene-earliest Pliocene “ Steno ” cudmorei Chapman (1917)

from the Black Rock Sandstone of Beaumaris, Victoria

(Fitzgerald, 2004b). Fordyce (1982) questioned the taxonomic

identity of “5?’ cudmorei (the holotype, P13033, being an iso-

lated tooth) and Fitzgerald (2004b) referred “S.” cudmorei to

Delphinidae, genus and species indeterminate. Chapman

(1917) assigned P13033 to Steno on the basis of the resem-

blance of its crown ornamentation to that seen in the teeth of

the extant Steno bredanensis Cuvier in Lesson, 1828 (e.g.,

Miyazaki and Perrin, 1994). Given that Steno is probably in a

basal position in the phylogeny of Delphinidae (Miyazaki and

Perrin, 1994; LeDuc et al., 1999) and that some of the pre-

sumed ancestors of Delphinidae, the Kentriodontidae (Barnes,

1978, 2002; LeDuc, 2002), possessed Steno-like crown orna-

mentation (e.g., Kellogg, 1966), the anastomosing striae on the

crown of P13033 (and P218283, P218284, P218286) are of

dubious use in assessing the phylogenetic affinities of isolated

teeth. Furthermore, non-delphinid small odontocetes such as

Lipotes vexillifer Miller, 1918 possess anastomosing wrinkling

on tooth crown enamel (Miller, 1918; Brownell and Herald,

1972; Barnes, 1985) which casts doubt on any perceived

taxonomic or phylogenetic signal present in these teeth.

The isolated teeth from Portland are assigned to

Delphinoidea incertae sedis. None of the Portland Pliocene

teeth share demonstrably close affinities with the holotype

tooth of “ Steno ” cudmorei.

Family Delphinidae Gray, 1821

cf. Tursiops sp. Gervais, 1855 sp.

Referred specimen. NMV P2 18266, virtually complete right periotic

(Fig. 6).

Description. P2 18266 is typically delphinid in possessing: (1)

posterior process of the periotic projects laterally and postero-

laterally; (2) longitudinal grooves on the articular facet of the

posterior process of the tympanic (this feature also occurs in

Monodontidae); (3) relatively low crista transversa; (4) internal

facial foramen opens at the same level as the tractus spiralis

foraminosus in the internal acoustic meatus; (5) a short, blunt,

rectangular anterior process of the periotic which in anterior,

dorsal and ventral views appears laterally compressed; (6) a

large fovea epitubaria for the accessory ossicle eliminates the

anterior bullar facet on the anterior process; (7) prominent

parabullary ridge; (8) inflated pars cochlearis; and (9) rela-

tively shallow internal acoustic meatus (Kasuya, 1973; Fordyce

et al., 2002). The first character is usually only seen in

Delphinidae but several taxa in the extinct delphinoid grade-

Erich M.G. Fitzgerald

A B

Figure 4. Miocene to Recent Kogiidae tympanies. A-B, Kogiidae gen. et sp. indet. (Pliocene Whalers Bluff Formation, Portland, Victoria,

Australia), incomplete left tympanic, NMV P2 18407 (AC). C-D, Kogiidae gen. et sp. undet. (Lower Pliocene Yorktown Formation, Lee Creek

Mine, North Carolina, U.S.A.), incomplete left tympanic, USNM 251118. E-F, Scaphokogia cochlearis (Upper Miocene Pisco Formation, Aguada

de Lomas level, Arequipa Department, Peru), incomplete left tympanic, USNM 452993. G-H, Kogiidae gen. et sp. undet. (Lower Pliocene

Yorktown Formation, Lee Creek Mine, North Carolina, U.S.A.), incomplete right tympanic, USNM 183008. 1-J, Kogia breviceps (Recent, Shelley

Beach, Victoria, Australia), incomplete left tympanic, NMV C24976. A, C, E, G, I, all in dorsal view. B, D, F, H, J, all in ventral view. Scale

bars equal 10 mm.

Pliocene marine mammals

C D

Figure 5. Miocene to Pliocene Physeteridae tympanies. A-B, Physeteridae gen. et sp. undet. (Lower Pliocene Yorktown Formation, Lee Creek

Mine, North Carolina, U.S.A.), right tympanic, USNM 183007. C-D, Orycterocetus crocodilinus (Middle Miocene Calvert Formation, Zone 14,

south of Randle Cliff Beach, Calvert County, Maryland, U.S.A.), right tympanic, USNM 22953. A and C in dorsal view. B and D in ventral view.

Scale bars equal 10 mm.

taxon Kentriodontidae possess a posterolaterally projecting

posterior process of the periotic (eg., Barnes and Mitchell,

1984; Dawson, 1996) as does Albireo whistleri (Albireonidae)

(Barnes, 1984). P218266 and the other odontocete periotics

described below possess all of the characters listed above,

justifying their assignment to Delphinidae. Table 3 presents

comparative measurements of selected dimensions for all

delphinid periotics described herein.

Discussion. Within Delphinidae, P218266 is most similar to

Tursiops and Lissodelphis. P2 18266 is similar to the periotics

of Tursiops in: (1) its overall size; (2) having the aperture of the

internal acoustic meatus opening at the same level as the

endocranial surface of the body of the periotic; (3) having a

deep internal facial foramen; and (4) having an aquaeductus

vestibuli located at the same level as the foramen for the

vestibular branch of the vestibulocochlear nerve. P2 18266

Erich M.G. Fitzgerald

Table 3. Measurements of delphinid periotics from the Whalers Bluff Formation and delphinid periotics from the Red Crag, England.

Measurements follow methodology of Kasuya (1973). All measurements are in mm.

NMV

P218264

P2 18265

P2 18266

P204352

P218481

Standard length of periotic, from tip of anterior process to posterior end of

posterior process, measured on a straight line parallel with cerebral border

28.00

26.66

32.50

29.94

29.40

Thickness of superior process at the level of upper tympanic aperture

Width of periotic across pars cochlearis and superior process, at the level of

11.00

10.00

11.90

12.14

11.58

upper tympanic aperture

Least distance between the margins of fundus of internal acoustic meatus

20.00

17.76

23.00

20.00

19.58

and of aperture of aquaeductus vestibuli

Least distance between the margins of fundus of internal acoustic meatus

2.56

2.16

1.58

3.00

2.50

and of aperture of aquaeductus cochleae

3.00

3.14

1.50

2.20

Length of the posterior bullar facet

11.00

12.46

12.62

Antero-posterior diameter of pars cochlearis

17.00

16.00

17.80

14.66

16.16

differs from Tursiops in: (1) the possession of a more acute

angle between the anterior process and pars cochlearis;

(2) having an aquaeductus cochleae positioned further from the

fenestra cochleae, and further dorsally on the endocranial

side of the pars cochlearis; (3) having a lower crista transversa;

(4) having a poorly developed septum between the tractus

spiralis foraminosus and the foramen for the vestibular branch

of the vestibulocochlear nerve; and (5) having a less rounded

pars cochlearis.

P2 18266 shares with the periotic of Lissodelphis : (1)

endocranial surface of the periotic bordering the posterior

margin of the internal acoustic meatus, aperture of aquaeductus

vestibuli, and aquaeductus cochleae, is uniformly flat; and

(2) aperture of the aquaeductus cochleae opens on the same

plane as the aperture of the internal acoustic meatus (note that

this condition is also seen in Steno). P2 18266 differs from the

periotic of Lissodelphis by: (1) being markedly larger in over-

all size; and (2) having a mediolaterally broader aperture of the

internal acoustic meatus.

The balance of features noted above indicates that P2 18266

is a delphinid with close affinities to Tursiops. This periotic is

not identified as undoubtedly as such due to the subtle differ-

ences between P2 18266 and the periotic of extant Tursiops spp.

Barnes (1990) provided a thorough review of the fossil record

of Tursiops. He recognised four fossil species of Tursiops-. T.

cortesii Sacco, 1891 (Italy; Late Pliocene, c. 1.75-3.5 Ma, and

possibly Early Pliocene, c. 5 Ma); T. astensis Sacco, 1891(Italy;

early Late Pliocene, c. 3-3.5 Ma); T. capellinii del Prato, 1898

(Italy; middle Pliocene, c. 3.5 Ma); T. ossenae Simonelli, 1911

(Italy; middle Pleistocene or late Pleistocene, c. 0.5-0. 8 Ma).

Other unnamed pre-Pleistocene records of Tursiops include:

aff. Tursiops from the Purisima Formation, California (Late

Pliocene, 1.8-3 Ma) (Barnes, 1977); and Tursiops sp. from the

Yorktown Formation, North Carolina (Early Pliocene, 3. 5-4.5

Ma) (Whitmore, 1994).

The record from the Pliocene of Victoria is the first prob-

able pre-Pleistocene fossil record of Tursiops from the

Southwest Pacific. Furthermore, this fossil occurrence provides

corroboration for Barnes’ (1990: 18) hypothesis that Tursiops

has been as geographically widespread during the last six

million years as it is at the present time.

Delphinus sp. Linnaeus, 1758 or Stenella sp. Gray, 1866

Referred specimen. NMV P2 18265, virtually complete left periotic

(Fig. 7).

Description. P2 18265 is smaller than P2 18266 (cf. Tursiops

sp.) (Fig. 6), closely matching the periotics of both Delphinus

and Stenella in overall proportions. Morphological similarities

between P2 18265 and Delphinus include: (1) relatively large

diameter of the aperture of the fenestra cochleae; and (2) aper-

ture of the aquaeductus vestibuli is ellipsoid to slit-like in out-

line and opens posteriorly. However, P2 18265 differs from

Delphinus in: (1) the suprameatal area of the periotic, lateral to

the aperture of the internal acoustic meatus, is less planar and

more convex; (2) the lateral wall of the internal acoustic

meatus lacks an elevated platform which obscures the vesti-

bular foramen in endocranial view; (3) the crista transversa is

lower; and (4) the aperture of the internal facial foramen is

narrower.

Discussion. Whitmore (1994) noted that it is very difficult to

distinguish between Delphinus and Stenella on the basis of

periotic morphology. Confounding generic identification of

P21265 is the fact that the periotics of Stenella show wide indi-

vidual variation (Kasuya, 1973). In both Delphinus and

Stenella, the aquaeductus cochleae opens at a similar position

on the posterior wall of the pars cochlearis. Most preserved fea-

tures indicate closer affinities with Stenella than Delphinus.

However, all of the identified differences between P2 18265 and

Delphinus are subtle, representing differences in degree rather

than kind. I do not advocate the definitive placement of

P2 18265 within either Delphinus or Stenella. In any event, the

somewhat intermediate morphology of P2 18265 between the

periotics of Delphinus and Stenella may indicate that P2 18265

is from an extinct genus closely related to both of the extant

genera in question. In either case, P2 18265 is the first record of

a periotic of the Delphinus-Stenella type recorded from the

Neogene of Australia.

Fossils representing Delphinus or Stenella have been

recorded from: Upper Member Almejas Formation, Baja

California Sur (latest Miocene to Early Pliocene, 3.5-6 Ma)

(Barnes, 1998); San Mateo Formation, California (Late

Pliocene marine mammals

Figure 6. cf. Tursiops sp. (Pliocene Whalers Bluff Formation, Portland, Victoria, Australia), right periotic, NMV P218266 (AC). A, ventral view.

B, cranial view. C, medial view. D, lateral view. Scale bar equals 10 mm.

Erich M.G. Fitzgerald

Figure 7. Delphinus sp. or Stenella sp. (Pliocene Whalers Bluff Formation, Portland, Victoria, Australia), left periotic, NMV P2 18265 (AC). A,

ventral view. B, cranial view. C, medial view. D, lateral view. Scale bar equals 10 mm.

Pliocene marine mammals

Miocene to Early Pliocene, 5-9 Ma) (Barnes et al., 1981);

unnamed blue clays at Waihi Beach, Hawera, New Zealand

(Early Pliocene, 3-3.6 Ma; Beu, 1995) (McKee and Fordyce,

1987; Fordyce, 1991a: 1262); Yorktown Formation, North

Carolina (Early Pliocene, 4.5 Ma) (Whitmore, 1994); Salada

Formation, Baja California Sur (Early to Late Pliocene, 3-5

Ma) (Barnes, 1998); Tirabuzon Formation, Baja California Sur

(middle Pliocene, 3-4 Ma) (Barnes, 1998); SAO Level of the

Pisco Formation, Peru (late Early to early Late Pliocene,

3. 0-4.0 Ma) (Muizon and DeVries, 1985; Muizon and

Domning, 2002); and San Diego Formation, California (Late

Pliocene, 1.8-3.4 Ma) (Barnes, 1973, 1977, 1998).

Genus and species undetermined A

Referred specimen. NMV P2 18264, virtually complete right periotic

(Fig. 8).

Description. P2 18264 differs from all previously described

delphinid periotics from the Pliocene of Portland in its relative-

ly good state of preservation, indicating less post-mortem trans-

port and abrasion, with fine surface details intact. P2 18264 is

distinct from P2 18265 and P2 18266 but intermediate in overall

size. Notable differences between P2 18264 and P2 18265 and

P2 18266 include: (1) a mediolaterally thickened periotic body

lateral to the pars cochlearis; (2) apex of anterior process with

distinct tubercle; (3) possession of two deep creases in the

anteromedial face of the anterior process; (4) aperture of the

internal acoustic meatus is mediolaterally compressed, such

that in endocranial view the meatus is more ellipsoidal and slit-

like in outline than that of either or the others; (5) the aperture

of the internal facial foramen is narrow; and (6) the aperture of

the aquaeductus vestibuli is so narrow that it appears closed.

Discussion. P2 18264 does not closely resemble the periotics of

any Recent delphinids in the Museum Victoria collections, nor

any of the Recent delphinid periotics figured by Kasuya (1973).

However, P2 18264 (Fig. 8) closely resembles two fossil del-

phinid periotics from the Plio-Pleistocene Red Crag of England

(P204352, P2 18481: Fig. 9). Both periotics were originally

identified as Globicephalus uncidens Lankester, 1864 (sensu

Lydekker, 1887) by persons unknown. The Globicephalus

uncidens periotic figured by Lydekker (1887: plate II fig. 11)

probably represents a Globicephala periotic, Globicephalus

being a junior synonym of Globicephala. However, P204352

and P2 18481 (Fig. 9) do not represent Globicephala periotics.

An incomplete delphinid periotic (CD 53) has been

described from late Neogene sediments of uncertain age on

Chatham Island, east of New Zealand (Fordyce and Campbell,

1990). The following features of CD 53 are shared with

P2 18264: well-developed, laterally expanded, parabullary

ridge with a globose, tubercle-like anterior apex; anteroventral

angle is rounded off; creases in ventrolateral parabullary ridge;

and short, broad, fan-like posterior process with heavily fis-

sured posterior bullar facet. Based on these similarities, it is

hypothesised that CD 53 is in the same genus, at least, as

P2 18264. Given the Pliocene age of P2 18264, and Plio-

Pleistocene age of P204352 and P2 18481, this taxonomic

assignment of CD 53 suggests a lowest Opoitian (Early

Pliocene) or younger age for the Chatham Island delphinid

periotic and its host sediments. Fordyce and Campbell

(1990: 62-63) suggested a Late Miocene or younger age for

CD 53. Pending the discovery of more complete cranial

material including periotics of this type, P2 18264 is referred

to an undetermined genus and species of Delphinidae (as are

P204352, P218481 and provisionally CD 53).

Order Carnivora Bowdich, 1821

Suborder Pinnipedia Illiger, 1811

Family ?Phocidae Gray, 1821

Genus and species indeterminate

Referred specimens. NMV P2 18465, incomplete left horizontal ramus

of mandible (Fig. 10). NMV P2 18273, isolated upper incisor or canine

tooth (not figured).

Description. P2 18465 is an incomplete left horizontal ramus

with a preserved length of 69 mm, depth at level of dorsal con-

cavity of 21 mm, and mediolateral thickness at level of poster-

ior alveolus for ml of 10 mm. The surface detail of P218465 is

well preserved relative to most of the other marine vertebrate

fossils recovered from the Whalers Bluff Formation. P2 18465

lacks all of the horizontal ramus anterior to the anterior alveo-

lus for p4 and all of the ascending and horizontal rami poster-

ior to the anteriormost corner of the fossa for m. masseter pars

profundus. No teeth are preserved in situ in the mandible. In

overall proportions, the ramus is lightly built. In posterior and

dorsal view, slight medial inflection of the ramus is visible. In

lateral aspect, there is a small mental foramen located ventral to

the position of the interalveolar septum between the anterior

and posterior alveoli of p4 (Fig. 10B). This position is almost

identical to that of the posteriormost mental foramen on a

mandible referred to Piscophoca sp. by Walsh and Naish

(2002). Such small mental foramina are also present on the

mandibles of Zalophus californianus Lesson, 1828 (Howell,

1929; pers. obs.). Immediately posterior to the posterior

alveolus of ml is a prominent dorsal concavity 25 mm long

(measured from the ml alveolus to the anterior margin of the

fossa for m. masseter pars profundus). This dorsal concavity

resembles that of Piscophoca. The preserved anterior region of

the fossa for m. masseter pars profundus differs from that

of Piscophoca in being dorsoventrally broader with a more

rounded outline.

P2 18273 represents an isolated incisor or canine tooth, 28

mm long; its mesiodistal width at a level just below the base of

the crown is 8 mm while its buccolingual width at the same

level is 6 mm. The crown has smooth enamel and is recurved

towards the apex. The root has a consistent thickness and is

buccolingually compressed.

Discussion. The pinniped fossils recovered from the Whalers

Bluff Formation do not include elements preserving unequivo-

cal synapomorphies of suprageneric pinniped taxa. Berta

(1991) and Berta and Wyss (1994) listed the possession of a

bony flange below the angular process of the mandible as an

unequivocal synapomorphy of Superfamily Phocoidea (sensu

Wyss and Flynn, 1993) but the posterior region of the mandible

is not preserved in P2 18465. However, P2 18465 is tentatively

Erich M.G. Fitzgerald

Figure 8. Delphinidae gen. et sp. undet. A (Pliocene Whalers Bluff Formation, Portland, Victoria, Australia), right periotic, NMV P2 18264 (AC).

A, ventral view. B, cranial view. C, medial view. D, lateral view. Scale bar equals 10 mm.

Pliocene marine mammals

Figure 9. Delphinidae gen. et sp. undet. A (Pleistocene-Pliocene Red Crag, Henley, England), right periotic, NMV P2 18481 (AC). A, ventral view.

B, cranial view. C, medial view. D, lateral view. Scale bar equals 10 mm.

Erich M.G. Fitzgerald

Figure 10. ?Phocidae gen. et sp. indet. (Pliocene Whalers Bluff Formation, Portland, Victoria, Australia), incomplete left mandible, NMV P2 18465

(AC). A, dorsal view. B, lateral view. C, medial view. Black arrow in B points to mental foramen. Scale bar equals 10 mm

referred to the Phocidae on the basis of its morphology and pro-

portions being most similar to the mandibles of phocid seals, as

opposed to otariids and odobenids. It remains possible that

P2 18465 represents an otariid mandible. If this were the case,

then a major rethinking of otariid evolutionary biogeography

would be necessary, as current estimates place the otariid

dispersal into the Southern Hemisphere at around the

Pliocene/Pleistocene boundary (Demere et al., 2003; contra

Repenning and Tedford, 1977, who indicated a latest Miocene

dispersal event at the earliest), and the age of P2 18465 (and

P2 18273) probably predates that horizon.

Given that P2 18465 is not similar in morphology to

Otariidae but shares certain features with some phocids (see

description and discussion below), there is no firm evidence to

suggest that the Portland mandible represents an otariid. The

fact that phocid seal fossils have previously been reported from

Pliocene-aged sediments in Victoria (Fordyce and Flannery,

1983) whereas otariids have not lends further support to the

assignment of P2 18465 to the Phocidae. However, P2 18465

and P2 18273 are not referred unquestionably to Phocidae

because the late Neogene fossil record of marine mammals in

the SW Pacific remains too poorly documented to provide any

absolute idea of the composition of the marine mammal fauna

during the Pliocene.

Among extant and fossil phocid mandibles, P2 18465 is

most similar to those of the Pliocene taxa Acrophoca lon-

girostris Muizon, 1981, Homiphoca capensis Hendey and

Repenning, 1972, and Piscophoca pacifica Muizon, 1981.

P2 18465 may be clearly distinguished from Acrophoca, as it

lacks the wide diastema between cheek teeth characteristic of

Acrophoca (Muizon, 1981). The Portland mandible can be fur-

ther distinguished from Homiphoca (Hendey and Repenning,

1972; Muizon and Hendey, 1980) by the possession of a

well-developed dorsal concavity posterior to ml. P2 18465 is

generally very similar to the mandible of Piscophoca (Muizon,

1981) in its overall proportions, relative length of the dorsal

concavity posterior to ml, subequal diameters of the alveoli

and relatively closely spaced alveoli along the tooth row.

However, it is not possible at this stage to determine whether

the Portland mandible belongs to a species of Piscophoca

or not.

The Australian fossil record of pinnipeds is currently poor.

Fordyce (1991b) summarised the state of knowledge at the

beginning of the 1990s, and virtually nothing has been added

since that time. The oldest fossil pinnipeds from the SW Pacific

are latest Miocene (c. 6 Ma) at the earliest and are from

Australia (Fitzgerald, 2004b). Fordyce and Flannery (1983)

provided a preliminary assessment of these fragmentary fossils

suggesting that they represented monachine phocids. The fos-

sils represent one ?incisor tooth (P16198), two right temporals

Pliocene marine mammals

(P160399 and P160441), two fused sacral vertebrae (P41759)

and an articulated series of eight thoracic vertebrae with five

ribs (P160433). None of these specimens has yet been

described and only one of the temporals (PI 60399) has

been figured (Fordyce and Flannery, 1983: 99). Recently, two

other pre-Pleistocene ?phocid fossils have been discovered:

P42523, isolated right metatarsal V; and P2 15759, isolated left

metatarsal V. Both P42523 and P215759 were derived from

beds immediately overlying a phosphatic nodule horizon at the

base of the Black Rock Sandstone (Beaumaris, Victoria), and

are thus early Early Pliocene in age. The exact relationships of

the phocids represented by temporals to extant Monachinae and

their fossil sister-taxa ( Acrophoca , Homiphoca and Pisco -

phoca) have yet to be determined. The report herein of two

probable phocid pinniped fossils from Portland brings the number

of known Australian pre-Pleistocene pinniped specimens to nine.

Conclusions

The fossil marine mammal assemblage from the Pliocene-aged

Whalers Bluff Formation is the first to be described in detail

from Australia. All marine mammal taxa represent members of

extant families and for the most part extant genera: Physeter,

Tursiops , and Delphinus or Stenella. Other taxa, of uncertain

affinities below family level, include a balaenid, balaenopterid,

a third undetermined genus of delphinid and a phocid pinniped.

The diversity of marine mammals in the Portland Pliocene

assemblage is impoverished relative to extant faunas, with at

least 18 marine mammal species regularly occurring in north-

west Bass Strait (Wameke in Menkhorst, 1995; pers. obs.).

Published details of other SW Pacific Pliocene marine mam-

mal assemblages are scanty (Fordyce, 1991a, 1991b;

Fitzgerald, 2004b). Only three Australian assemblages provide

a reasonable basis for comparison with the Portland Pliocene

assemblage; the Beaumaris Local Fauna (Victoria), Grange

Burn assemblage (Victoria) and Cameron Inlet assemblage

(Flinders Island, Bass Strait). However, only the Cameron Inlet

assemblage is approximately contemporaneous with the

Portland Pliocene assemblage (about 2. 5-4. 8 Ma), the

Cameron Inlet Formation being late Early to Late Pliocene

(about 2.0-4.0 Ma; Fitzgerald, 2004b and references therein).

The Beaumaris Local Fauna spans the Miocene-Pliocene

boundary, with an age range for the Black Rock Sandstone of

about 4.5-5. 8 Ma (Dickinson et al., 2002; Wallace et al., 2005).

The Grange Burn assemblage is perhaps slightly younger than

the Beaumaris Local Fauna, with the Grange Burn Formation

being Early Pliocene (>4.35-5.3 Ma) (Dickinson et ah, 2002;

Fitzgerald, 2004; Wallace et ah, 2005). Both the Beaumaris

Local Fauna and the Grange Burn assemblage are (at least in

part) phosphatic nodule bed deposits.

A significant problem in making meaningful comparisons

between the Portland Pliocene assemblage and the other assem-

blages listed above lies in the great disparity in numbers of

specimens collected. Whereas the Portland Pliocene and

Cameron Inlet assemblages are known from 30-40 specimens,

the Beaumaris Local Fauna and Grange Bum assemblage are

known from hundreds of fossils. Nevertheless, with this bias in

mind some preliminary comparisons can be made.

hi all four assemblages almost all marine mammal families

present are extant. The sole exception to this is the occurrence

of the paraphyletic family ‘Cetotheriidae’ (Fordyce and Barnes,

1994; Fordyce, 2003; Geisler and Luo, 1996; Geisler and

Sanders, 2003; Kimura and Ozawa, 2002) in the Beaumaris

Local Fauna and Grange Bum assemblage (Fitzgerald, 2004b).

At the generic level, there appear to be some differences

between the known diversity of marine mammals in the

Portland Pliocene assemblage/Cameron Inlet assemblage and

the Beaumaris Local Fauna/Grange Bum assemblage. In the

latter two, extant genera include cf. Eubalaena, Balaenoptera,

Megaptera, Physeter and cf. Mesoplodon. The delphinids from

the phosphatic nodule bed assemblages do not appear to be

closely related to extant genera, contrary to earlier assessments

(e.g., Chapman, 1917). Rather, delphinid periotics and middle

ear ossicles from the Beaumaris Local Fauna possess a rela-

tively high number of primitive characters with respect to

extant Delphinidae. This is markedly different from the

Portland Pliocene assemblage in which most described del-

phinid periotics seem to represent extant genera. Other appar-

ently archaic aspects of the Beaumaris Local Fauna/Grange

Bum assemblage include the high diversity of physeterid taxa

(three genera, including a small form similar to the form genus

Scaldicetus and another similar to Physeterula dubusii Van

Beneden, 1877) relative to the present (one genus).

The Cameron Inlet assemblage appears to be essentially

modem in aspect based on fossils recovered to date. Fordyce

(1991b: 1183) listed ziphiids (including Mesoplodon sp., based

on isolated periotics), physeterids (cf. Physeter macrocephalus)

and balaenopterids in this assemblage. Fitzgerald (2004: 198)

included cf. Balaenoptera, cf. Megaptera and a possible del-

phinid. Sutherland and Kershaw (1971) reported an incomplete

skull (NMV P23961) as Ziphius sp. but Fordyce (1984b: 939)

later questioned this assignment and re-identified NMV

P23961 as ? Mesoplodon sp. The Cameron Inlet assemblage is

generally similar to the Portland Pliocene assemblage which is

perhaps not unexpected given their similar geological age and

geographic proximity.

It has previously been noted that latest Miocene through

Pliocene marine mammal assemblages across the globe include

extinct, often aberrant, genera and families and formerly wider

(in some cases unexpected) geographic ranges for extant taxa

that today have restricted geographic distributions (Fordyce et

al., 2002 and references therein). Indeed, the apparently recent

evolution of marine mammal faunas of modem aspect led

Fordyce and colleagues (2002) to suggest that among cetaceans

at least a major ecological change occurred about 3-4 million

years ago. This change is marked by the last appearance in the

fossil record of genus and family-level taxa displaying rela-

tively primitive grades of evolution (e.g., Albireonidae,

Herpetocetus : Barnes, 1984; Whitmore, 1994; Oishi and

Hasegawa, 1995; Barnes and Furusawa, 2001; Fordyce and

Muizon, 2001) as well as novel morphological adaptations and

inferred palaeoecology (e.g., Odobenocetopsidae, Austral-

odelphis : Fordyce et al., 2002; Muizon and Domning, 2002).

The early Pliocene is marked by a global warming trend

beginning at c. 4.5-5. 5 Ma with the rapid development of full-

scale Northern Hemisphere and Antarctic glaciation occurring

Erich M.G. Fitzgerald

in the late Pliocene at approximately 2.75-3.2 Ma (Zachos et

al., 2001; Ravelo et al., 2004; Wara et al., 2005). Gallagher and

colleagues (2003) presented data indicating that the earlier

Pliocene (3. 1-5.3 Ma) was a time of generally stable marine

temperatures in Bass Strait with surface temperatures per-

haps as much as 3°C warmer than today (Ravelo et al.,

2004). The Late Pliocene in Bass Strait was characterised by a

fluctuating, overall cooler climate than the preceding Early

Pliocene (Gallagher et al., 2003). As Fordyce and colleagues

(2002) have indicated, climatic and oceanic changes associ-

ated with rapid global cooling at c. 3.2 Ma were likely

major influences on the evolution of the modem marine

mammal fauna. A larger sample of marine mammal fossils from

Pliocene-aged assemblages in south-east Australia with finer

resolution of stratigraphic distribution of marine mammal

taxa during the Pliocene is required for more detailed

correlations between Pliocene marine mammal and climatic

evolution.

The description of the Pliocene marine mammal assemblage

from Portland alleviates the dearth of information on SW

Pacific marine mammal assemblages during the late Neogene.

The occurrence of extant cetacean taxa ( Balaenoptera ,

Physeter, Delphinus/Stenella and Tursiops ) in the Whalers

Bluff Formation (>2. 5-4.8 Ma) (and Cameron Inlet Formation)

indicates that the marine mammal fauna off south-east

Australia had begun to take on a modem aspect by at the

earliest 4.8 Ma and latest around 2.5 Ma. Indeed, most of the

cetacean species still exist in the seas off Portland (Wameke in

Menkhorst, 1995; pers. obs.). That the latter cetacean taxa

occur in Early-Late Pliocene deposits in the SW, SE and NE

Pacific, and NW Atlantic, suggests that several extant cetacean

genera were widespread in the world’s ocean basins prior to

about 2.5 Ma.

Acknowledgements

Our rapidly improving knowledge of late Neogene fossil

marine vertebrates off southeast Australia would not be

possible without the collecting efforts of Mr Sean Wright and

his donation of hundreds of fossils to Museum Victoria, for

which he is thanked. The Vertebrate Palaeontology and

Mammalogy departments of Museum Victoria are thanked for

providing research facilities and access to specimens. D.J.

Bohaska is thanked for his assistance with access to specimens

during a visit to the National Museum of Natural History

(Smithsonian Institution) and R. Purdy assisted with photo-

graphic facilities there. The Museum Victoria Library, with the

National Museum of Natural History (Smithsonian Institution)

Remington Kellogg Library for Marine Mammalogy, were crit-

ical in providing access to some otherwise intractable literature.

Dr T.A. Darragh is thanked for discussions on late Neogene

biostratigraphy. This paper was greatly improved by the helpful

review by Ewan Fordyce and editorial comments from Gary

Poore. This work forms part of a Ph.D. thesis undertaken in the

School of Geosciences, Monash University and Museum

Victoria, which was financially supported by an Australian

Postgraduate Award.

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Memoirs of Museum Victoria 62(1): 91-99 (2005)

ISSN 1447-2546 (Print) 1447-2554 (On-line)

http://www.museum.vic.gov.au/memoirs/index.asp

Two new Middle Miocene spatangoids (Echinoidea) from the Murray Basin,

South Australia

Francis C. Holmes 1 , Christopher Ah Yee and Janice Krause 2

‘15 Kenbry Road, Heathmont, Victoria 3135, Australia, and Invertebrate Palaeontology, Museum Victoria, PO Box 666,

Melbourne, Victoria 3001, Australia (fholmes@bigpond.net.au)

2 P.O. Box 581, Hamilton, Victoria 3300, Australia

Abstract Holmes, F.C., Ah Yee, C., and Krause, J. 2005. Two new Middle Miocene spatangoids (Echinoidea) from the Murray

Basin, South Australia. Memoirs of Museum Victoria 62(1): 91-99.

Two new spatangoid taxa are described from the Glenforslan Formation cropping out in the Murray River cliffs near

Blanchetown, South Australia. One taxon, Murraypneustes biannulatus gen. et sp. nov., a large species of spatangoid

with two ‘peripetalous’ fascioles (one circling the margin and the other close to the distal end of the relatively short

petals), two distinct sizes of aboral primary tubercles, and a depressed apical system. The other spatangoid described,

Spatagobrissus dermodyorum sp. nov. differs from the only other fossil species of this genus recorded from Australia,

S. laubei (Duncan, 1877), in having a much shorter labrum, markedly larger peristome and periproct and larger primary

tubercles within the peripetalous fasciole.

Keywords Echinoidea, Spatangoida, Murrraypneustes, Spatagobrissus, new taxa, Middle Miocene, South Australia

Introduction

Of all the Australian Tertiary sedimentary sequences that con-

tain extensive echinoid faunas, the 150 km of Murray River

cliffs, from Overland Comer, east of Waikerie, to Murray

Bridge, South Australia, have over the last 120 years been more

comprehensively studied by palaeontologists, students and

amateur collectors than any other similar area. In the Miocene

stratigraphic sequences along the Murray River and elsewhere

in Australia, species belonging to the Spatangoida constitute

approximately 50 percent of the recorded taxa of irregular

echinoids. In view of the number of spatangoids occurring in

this section of the Murray River cliffs, the discovery in 2003 of

three specimens of a new genus belonging to this order, seem-

ingly unrelated to any other genus known from the continent’s

fossil record, was unexpected.

The specimens were found within 300 m of each other in a

single bed of the Glenforslan Formation, cropping out on the

left bank of the Murray River, 7 km NNE of Blanchetown,

South Australia [Museum Victoria locality PL3203]. Further

investigation of the surface exposure of the formation in the

general vicinity of this discovery failed to produce any

additional specimens of the new genus.

Materials and methods. Specimen numbers prefixed P, on

which the studies are based, are housed in the Invertebrate

Palaeontology collection, Museum Victoria (NMV). In addition

to type material, the new species of Spatagobrissus is repre-

sented by several specimens in private collections. Measure-

ments were made with a dial calliper to an accuracy of 0. 1 mm.

Parameters are expressed as a percentage of test length (%TL)

or test width (%TW).

Age and stratigraphy

The Glenforslan Formation, synonymous with the Lower

Morgan limestone, conformably overlies the Finniss Formation

and is of early Middle Miocene (Batesfordian, Langian) age.

The thickness of the unit is relatively consistent at 13-15 m

although this is reduced in southern exposure due to post-

Middle Miocene uplift and subsequent erosion. The formation

is sublithified to lithified, weathering to whitish-cream colour

in outcrop (Lukasik and James, 1998). It is composed of cycles

of mollusc-bryozoan floatstone, with a microbioclastic pack-

stone matrix, grading upward into Celleporaria rudstone tops

(infaunal bivalve and gastropod-rich microbioclastic matrix

with large branching and sheeted Celleporaria) which also

contain pectens and oysters. Echinoids tend to be found at or

above the rudstone-floatstone contact at the base of the cycles,

the latter containing delicate branching and uni-laminar sheet

bryzoans of 1-3 cm length. Sediments are pervasively mottled,

obscuring all physical sedimentary textures. The middle

Francis C. Holmes, Christopher Ah Yee and Janice Krause

Glenforslan Formation is interpreted as being deposited in

relatively shallow waters, possibly less than 10 m, based on the

presence of calcareous algae and mixotrophic foraminifers

(Lakasik, pers. com. 2005). It form s part of the richest warm-

water biotic record from southern Australia at a time of maxi-

mum transgression of the sea across the continental shelf

(McGowran and Li, 1994, and papers cited therein).

The three specimens of the new genus were found about 7.4

m above the base of the formation, approximately 2 m above

the Lepidocyclina Zone.

Associated fauna

Nineteen species of echinoids have been recorded from the

Glenforslan Formation within 500 m upstream and downstream

of PL3203 (Table 1), compared with 28 confirmed species

known to occur within the Morgan Group (Glenforslan, Cadell,

and Bryant Creek Formations).

Table 1. Echinoids recorded within the vicinity of locality PL3203.

Letters in brackets indicate the frequency of occurrence of each

species. [A], abundant; [C], common; [F], fairly common; [U], uncom-

mon; [R], rare. References to authors and supporting literature cited

below, but not listed in the main text references, can be found in

Holmes (1993).

Cidaroida

Goniocidaris murrayensis Chapman and Cudmore, 1934 [C]

Arbacoida

Murray echinus paucituberculatus (Gregory, 1890) [F]

Temnopleuroida

Cryptechinus humilior ( Bittner, 1892) [C]

Ortholophus morganensis Philip, 1969 [C]

O. pulchellus (Bittner, 1892) [C]

Clypeasteroida

Monostychia australis Laube, 1869 [A]

M. sp. ‘C’ in Holmes, 1999 [F]

Scutellinoides patella (Tate, 1891) [C]

Spatangoida

Brissopsis tatei Hall, 1907 [U]

Brissus sp. nov? [R]

Cyclaster archer i (Tenison Woods, 1867) [C]

Eupatagus rotundus Duncan, 1877 [U]

Eupatagus sp. indet. [U]

Hemiaster (Bolbaster) planedeclivis Gregory, 1890 [C]

Lovenia cf. forbesi (Tenison Woods, 1862) [C]

Murraypneustes biannulatus gen. et sp. nov. [R]

Pericosmus compressus (Duncan, 1877) [R]

Protenaster antiaustralis (Tate, 1885) [U]

Spatagobrissus dermodyorum sp. nov [F]

Systematic Palaeontology

Order Spatangoida Claus, 1876

Suborder Micrasterina Fisher, 1966

Family Incertae sedis

Remarks. The combination of generic features, particularly the

presence of a marginal ‘peripetalous’ fasciole, intermittent hor-

izontal fasciole bands and a rudimentary non re-entrant

peripetalous fasciole clear of the distal ends of paired petals,

clearly distinguish the new genus Murraypneustes from virtu-

ally all other taxa assigned to the Micrasterina, in particular the

22 genera included in the Asterostomatidae Fisher, 1966. Only

one of these genera, Asterostoma Agassiz, 1847, has tenta-

tively been retained in the Asterostomatidae (together with

Stomaporus Cotteau, 1888, a genus originally assigned to the

Brissidae Gray, 1855) by Smith et al. (2003). Of the remaining

21 genera, Smith et al. have conditionally reassigned 13 to

other families, only six of which are included in the

Micrasterina. The remaining eight are listed as incertae sedis or

as belonging to an unnamed taxon. Until a detailed revision of

these latter genera is published, it is considered imprudent to

assign the new genus to a specific family.

Murraypneustes gen. nov.

Type and only known species. Murraypneustes biannulatus sp.

nov.

Diagnosis. Large ovoid spatangoid with centrally depressed

adapical surface, apex well posterior of centre. Apical system

ethmolytic with 4 gonopores. Aboral primary tubercles of 2 dis-

tinct sizes, small and randomly spaced, the larger proximal to

the ambitus. Labrum long, narrow, partially tuberculate,

extending to third ambulacral plate. Two ‘peripetalous’

fascioles present; one marginal, passing above the periproct

(pseudolateral); the second, rudimentary, non re-entrant and

clear of the distal ends of paired petals. Intermittent horizontal

fasciole bands also occur between the 2 ‘peripetalous’ fascioles.

Subanal fasciole in contact with marginal periproct.

Etymology. For the Murray River cliffs, the origin of the fossils,

and “pneustes”, a common suffix used for spatangoid

echinoids. Gender masculine.

Remarks. The following analysis of morphological features of

genera similar to Murraypneustes gen. nov. is based primarily

on Mortensen (1950a) and Smith et al. (2003). Although

approximately 30 genera within the Micrasterina have been

investigated, only eight warranted further scrutiny; four cur-

rently unassigned to a family by Smith et al. (2003),

Elipneustes Koehler, 1914, Eurypatagus Mortensen, 1948,

Linopneustes A. Agassiz, 1881, and Platybrissus Grube, 1865;

three belonging to the Maretiidae (Lambert, 1905), Eupatagus

L. Agassiz, 1847, Mazzettia Lambert and Thiery, 1915 and

Spatagobrissus H. L. Clark, 1923; and Macropneustidae genus

Lajanaster Lambert and Sanchez Roig, 1924.

Using a broad comparison of 38 features, Linopneustes

stands out from the other seven genera as having closest affin-

ity with Murraypneustes ; four of its recorded six species,

L. longispinus (A. Agassiz, 1878), L. fragilis (de Meijere,

1903), L. spectabilis (de Meijere, 1903), and L. brachipetalus

Mortensen, 1950b having distinct marginal peripetalous

fascioles passing above the periproct. In the other two,

L. murrayi (A. Agassiz, 1879) and L. excentricus de Meijere,

1903, the peripetalous fasciole is not marginal but somewhat

higher up on the test (Mortensen, 1950a: 221). Although

L. fragilis has multiple fasciole bands around the ambitus,

Two new middle Miocene spatangoids

L. murrayi a rounded margin (Smith, pers. com. 2005) and

L. longispinus relatively short closing petals; Murmypneustes

is distinguished by its centrally depressed aboral surface form-

ing four apices (domed on Linopneustes ) with the highest point

of the test posterior to the apical disk (anterior in Linopneustes ),

the presence of two ‘peripetalous’ fascioles and intermittent

horizontal fasciole bands, two distinct sizes of small randomly

spaced aboral primary tubercles, the larger restricted to the

area outside the upper ‘peripetalous’ fasciole, and a prominent

angular subanal fasciole.

Based on the same criteria, three other genera show a mod-

erate degree of morphological similarity to Murraypneustes,

namely Elipneustes, Mazzettia, and Eupatagus.

Elipneustes, however, can be distinguished by its very long,

parallel- sided, open-ended, flush petals with conjugate pore

pairs; single, narrow, marginally situated peripetalous fasciole;

peristome situated immediately below the apical disk; small

thickset plastron with minimal posterior swelling; and much

larger primary tubercles scattered over all the aboral inter-

ambulacra.

Mazzettia, a poorly known fossil genus, has an elongated

heart-shaped test with a low sharp margin, very long weakly-

bowed petals closing distally, no recorded peripetalous fasciole

and only occasionally a weak shield-shaped subanal fasciole,

an elongated labrum just reaching the relatively small plastron,

and random but closely spaced coarse tubercles aborally.

Eupatagus, although possessing well developed peri-

petalous and subanal fascioles is easily categorised by its lack

of an anterior sulcus, predominately short lanceolate closed

petals, primary tubercles of varying density restricted to the

area within the peripetalous fasciole in aboral interlambracra

1-4, and very small evenly spaced tubercles distally over the

remainder of the aboral surface. Comparison of other features

is difficult because of variability among the very large number

of described species. In particular, the eight Australian fossil

species vary considerably in profile, are generally more round-

ed, and have an extremely wide range of primary tubercle

densities when compared with the type species on which the

generic description is based.

Two other genera, Platybrissus and Eurypatagus, are distin-

guished by their complete lack of fascioles, although the former

may have a subanal fasciole present in juvenile specimens.

Lajanaster, although depressed aborally, has no anterior

sulcus, a relatively sharp ambitus, a markedly narrow plaston,

and primary tubercles confined to the posterior column of

anterior and lateral interambulacra within the peripetalous

fasciole.

Spatagobrissus was included in the comparative analysis,

primarily as a new species of the genus occurs at the same

locality (PL3203) as Murraypneustes. In most respects the for-

mer is very similar to Eupatagus but has shorter petals and only

small tubercles over the whole of the aboral surface.

Murraypneustes biannulatus. sp. nov.

Figures 2A-F, 3A-C, 4A, B, 5

Type material. Holotype, NMY P3 12370 from early Middle Miocene

Glenforslan Formation (Batesfordian), Morgan Group, 7 km NNE of

Murray River Lock 1, Blanchetown, South Australia [NMV locality

PL3203].

Paratypes, NMY P3 12371 and P3 12372 from the same location.

Diagnosis. As for genus.

Description. Test moderately large, ovoid in outline with shal-

low anterior sulcus and pointed, slightly truncated posterior.

Specimens range from 72 to 81 mm in length, with maximum

width 81-86%TL occurring at 45%TL from anterior ambitus.

Test 44.1%TL high (uncompressed specimen) with apex of all

specimens well posterior of centre, 63-67%TL from anterior

ambitus.

Centre of test on adapical surface depressed around apical

disk and proximal end of paired petals to form minor apices in

interambulacra 1, 4 and 5, and conjointly, a raised area across

ambulacrum III and interambulcra 2 and 3. Adoral surface

mildly concave in vicinity of peristome with ambulacrum III

slightly recessed anteriorly and the plastron forming a fairly

pronounced keel posteriorly, terminating at the anterior edge of

the subanal fasciole.

Primary tubercles on adapical surface of 2 distinct sizes,

both widely and randomly spaced. Larger of the two restricted

to the distal 35% of the radius on interambulacrum 5, and 25%

elsewhere. Adorally, larger primary tubercles closely and

evenly spaced throughout, with exception of naked areas in

ambulacra I and V and phyllode plates of ambulacra II, III and

IV. Overlapping scrobicules on adoral surface form distinct

diagonal ridges. Small tubercles closely spaced immediately

below ambitus increase in size to that of larger primary

tubercles below curvature of margin. Large primary tubercles,

perforate with undercut mamelon and crenulated platform, and

maximum scrobicular diameter of approximately 2.5 mm,

twice size of smaller counterparts. Ring of scrobicular tubercles

not always present.

‘Peripetalous’ and subanal fascioles present, the former,

though not continuously visible on any specimen clearly

passes above periproct, while latter is distinctly angular, form-

ing hexagonal outline where in contact with lower edge of

periproct. Intermittent horizontal fasciole bands also present

laterally above and parallel to marginal ‘peripetalous’ fasciole.

Uppermost very narrow and more continuous fasciole,

although clear of distal ends of petals, appears to be a rudi-

mentary peripetalus fasciole not indented interradially (Fig. 3).

Apical system anterior of centre, 39.5-42.2%TL from anter-

ior ambitus to centre of disk, level or slightly below proximal

end of paired petals. Ethmolytic, with 4 small closely spaced

gonopores approximately 0.3 mm in diameter, anterior pair

closer together than posterior pair. Detail of ocular plates

indeterminate. Hydropores numerous, approximately 70

visible in one specimen, centrally located but extending

between posterior pair of gonopores and possibly ocular plates

I and V (Fig. 4A, B).

Petals lanceolate, moderately wide at midlength, closed dis-

tally, situated in gentle concave depressions incorporating

adradial edges of adjacent interambulacra and continuing prox-

imally across apical disk. Anterior paired petals shorter than

posterior pair, extending on average 60% of the radius meas-

ured along the surface of the perradial suture from centre of

Francis C. Holmes, Christopher Ah Yee and Janice Krause

apical disk to ambitus; posterior pair about 56% radius. Inner

pores of petals oval, outer pores slot-like, slightly curved and

50% wider. Pore pairs not conjugate but linked by a fine ridge

which extends along both sides of each pore (Fig. 5). Maximum

width of interporiferous zone slightly more than twice width of

poriferous zone. Anterior paired petals diverge at approxim-

ately 135° and contain on average 23 pore pairs, posterior

petals 297° and 26 pairs. Secondary tubercles extend randomly

across interporiferous and poriferous zones and for a distance

outside petals without primary tubercles. Ambulacrum III not

petaloid, basically flush with adjoining interambulacra for

about 50% radius, then gradually becoming concave towards

anterior sulcus. Other details unknown, no sign of pores or

regularly spaced tubercles being visible on specimens.

Peristome reniform, centre situated 27-30%TL from

anterior ambitus, longitudinal dimension approximately

6.5%TL, transverse dimension 12%TL. Phyllodes short and not

particularly well developed.

Labrum long and narrow, averaging 20.5%TL, slightly

curved at junction with peristome and abutting the plastron at

centre of third pair of adjacent ambulacral plates. Numerous

small tubercles adjacent to peristome with a few larger ones

towards the posterior end (Fig. 2C).

Plastron closely tuberculate, width approximately 75%

length measured from posterior edge of labrum to anterior edge

of subanal fasciole. Strong posterior taper suggests sixth and

subsequent plates of ambulacra I and V indent behind paired

episternal plates.

Periproct opening marginal, not visible from above, tear

shaped, slightly wider than high, set in a slight truncation

approximately 65° to the horizontal.

Etymology, biannulatus (L) - two-ringed, referring to the pres-

ence of two ‘peripetalous’ fasciole rings.

Family Maretiidae

Spatagobrissus H. L. Clark, 1923

Type species. Spatagobrissus mirabilis H. L. Clark, 1923, by

original designation.

Diagnosis. See H. L. Clark (1923: 402)

Spatagobrissus dermodyorum sp. nov

Figures 6A-E, 7A-C, 8A-E

Type Material. Holotype. NMV P3 12570 from early Middle Miocene

Glenforslan Formation (Batesfordian), Morgan Group, in the vicinity

of NMV locality PL3203, 7 km NNE of Murray River Lock 1,

Blanchetown, South Australia.

Paratypes, NMV P312571-P312373 from the same general area.

Other material used for statistical purposes is held in Museum Victoria

and private collections.

Description. Test small, subcircular in outline with minimal

posterior truncation and no anterior sulcus. Specimens range

30.0-45.5 mm in length with maximum width 82-90%TL

occurring 51-58 %TL from anterior ambitus. Maximum

height 49.5-60%TL at 52.6-65.5%TL from anterior

ambitus. Adapical surface moderately inflated, evenly curved

transversely above well-rounded margin with ambitus situated

at about 30%TH. Adoral surface very mildly convex but with

prominent posterior keel caused by sharp rise of ambulacra I

and V posterior to centre. In lateral view, posterior truncation

covers about 35%TH.

Apical system ethmolytic with 4 genital pores, centre

31.3-38.6%TL from anterior ambitus (Fig. 7A). Paired petals

short (26.5-32.5%TL measured along surface of perradial

suture from centre of apical disk), narrow (7.0-9.0%TL), lance-

olate, closing to closed, posterior pair marginally longer than

anterior pair. Anterior pair diverge at about 135°, posterior pair

310°. Pore pairs conjugate, inner pores oval, outer-tear shaped.

Anterior row of pore pairs in anterior paired petals distinctly

narrower than posterior row and atrophied adapically.

Interporiferous zone up to 1.5 times width of poriferous zone at

widest point. Ambulacrum III flush adapially, with 2 rows of

indistinct longitudinally orientated pore pairs and interporifer-

ous zone containing few secondary tubercles and numerous

miliaries.

Peripetalous fasciole subcircular, not indented. Numerous

small, randomly spaced perforate, crenulate, primary tubercles

occur in interambulacra within fasciole. Outside fasciole,

tubercles in posterior half of test very small, but anterior to

centre, gradually increasing in size towards interambulacra

2 and 3.

Peristome reniform, mildly sunken, width 16.0-19. 3%TL,

length 8.9-10.3%TL with anterior border 23.4-26. 8%TL from

anterior ambitus. Phyllodes moderately developed with slot-

shaped pores in circular depressions. Labrum short and wedge-

shaped extending only to centre of second pair of adjacent

ambulacral plates. Anterior edge raised above surrounding

ambulacra and slightly projecting over peristome. Miliary

tubercles present with few secondary tubercles in anterior half

(Fig. 7B).

Plastron long, width about 55-60% length, with ambulacral

plates indenting posteriorly. Subanal fasciole circular to trans-

versely oval, enclosing 3 pore pairs each side of interradial

suture, and with slight anterior projection at posterior end of

prominent plastronal keel. Posterior edge of fasciole margin-

ally clear of periproct opening. Adorally, ambulacra I and V

relatively wide, covered with very fine, randomly spaced

miliary tubercles up to sixth plate, then by tubercles of similar

size to rest of adoral surface.

Periproct, tear-drop shaped, generally positioned vertically

on truncated posterior margin but slightly visible from

above on some specimens; height 17.1-19.1%TL, width

13.2-16.0%TL.

Etymology. Named for Michael and Marie Dermody, owners of

Glenforslan Station.

Remarks. Spatagobrissus dermodyorum sp. nov. differs pri-

marily from the Middle Miocene Port Campbell Limestone

species, Spatagobrissus laubei (Duncan, 1877), in having

narrower test with more posterior maximum width (Fig. 8A),

markedly larger peristome and periproct (Fig. 8D, E), and very

much shorter labrum (Fig. 8B). In addition, anterior paired

petals are shorter and posterior petals longer (Fig. 8C), with

divergent angle of latter greater than S. laubei. Aboral primary

Two new middle Miocene spatangoids

tubercles larger within peripetalous fasciole and interambulacra

2 and 3, while fine tubercles outside fasciole on posterior half

of test are much smaller in diameter. Adorally, plastron wider

and longer, and ambulacra I and V narrower.

The extant type species Spatagobrissus mirabilis is charac-

terised by a larger (up to 110 mm long) and less inflated test,

more posteriorly located apical system in line with maximum

width, greater area enclosed by peripetalous fasciole, shorter

peristome, and periproct situated on an obliquely truncated

surface below the ambitus. Primary tubercles within the

peripetalous fasciole of S. mirabilis are also larger and more

closely spaced than in S. dermodyorum.

Spatagobrissus incus Baker and Rowe, 1990, an extant

species endemic to southeast Australian waters, particularly

between Flinders Island (Tasmania) and western Spencer Gulf,

South Australia, has a larger and more rounded test (up to 80

mm long) and, similar to S. mirabilis, more posteriorly located

apical system and greater area enclosed by peripetalous

fasciole.

Compared with S. dermodyorum, it also has a much

wider and longer plastron and narrower adoral ambulacra

I and V. Miskelly (2002: 156) noted two pairs of pore

pairs occur in each side of the subanal fasciole, a feature also

recorded for S. laubei (McNamara et al., 1986: 80). This

contrasts with the three pairs found on S. dermodyorum

(Fig. 1C).

Discussion

The major diagnostic features of Murraypneustes, particularly

the position of the two ‘peripetalous’ fascioles, the intermittent

horizontal fasciole bands, and the random pattern and separ-

ation of two distinct sizes of primary tubercles across the

aboral surface, give little indication of its lineage. Certainly,

within the Australian Cenozoic sequences that predate the early

Middle Miocene Glenforslan Formation, all the 13 recorded

genera of Micrasterina have their peripetalous fasciole close or

in contact with the paired petals. Only the brissid Cyclaster

is recorded as having developed multiple fascioles in some

specimens (McNamara et al., 1986: 68).

Similarly, there are no extant genera in Australian

waters that have any specific combination of characters that

link them to Murraypneustes. Even the extant species

Linopneustes brachipetalus, found off the east coast of

Australia, has long petals in contact with its marginal

peripetalous fasciole.

The lack of any juvenile specimens of the new genus, or

indeed any marked variation in the size of the three known

specimens, precludes any useful comment on the disposition

and specific function of its somewhat unusual arrangement of

fascioles, as such development takes place at a very early stage

of ontogeny.

Excluding Murraypneustes, only Hemiaster, of the nine

spatangoid genera known to occur in the Glenforslan

Formation sequence which embraces locality PL3203 (Table

1), has no extant record in Australian waters. The eight remain-

ing genera are today almost exclusively benthic filter feeders,

living inshore or on the continental shelf. Five, Brissopsis,

Brissus, Cyclaster, Lovenia and Pericosmus, occur in tropical

waters, and three, Eupatagus, Protenaster and Spatagobrissus

in temperate waters (Rowe and Gates, 1995). Species of these

eight extant genera, with the possible exception of Cyclaster,

are known to occur at depths of less than 20 m in Australian or

New Zealand waters. This depth range is consistent with the

sedimentary deposition of the Glenforslan Formation. On the

other hand, Indo-Pacific species of Linopneustes, including

L. brachypetalus, are found at depths exceeding 270 m (range

272-1788 m), with only the West Indies species, L. longispinus,

extending up into sublitoral waters (70-570 m) (Mortensen,

1950a).

Based on the available evidence, it is reasonable to assume

Murraypneustes dermodyi was a benthic filter feeder inhabiting

relatively shallow, warm (?sub-tropical) waters.

Acknowledgements

We are indebted to David Holloway (Invertebrate Palaeontol-

ogy, Museum Victoria) for valuable advice and support during

the preparation of this manuscript, and to Kenneth McNamara

(Western Australia Museum), Rich Mooi (California Academy

of Sciences) and Andrew Smith (Natural History Museum,

London), for suggesting improvements to the manuscript. Jeff

Lukasik (Petro-Canada) is thanked for providing specific strati-

graphic information and Ashley Miskelly (Blackheath, NSW)

for details of extant echinoids from Australian waters. Michael

and Marie Dermody and Donald and Miriam Griffen

(Blanchetown District, South Australia) are also thanked for

permission to collect on their properties. As always, Val Hogan

and Sandra Winchester (Library, Museum Victoria) were

helpful with access to references.

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Figure 1. A, B, general location maps; C, map of the Murray River between Waikerie and Swan Reach,

South Australia, showing locality of NMV locality PL3203, north of Blanchetown.