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The Silurian and Devonian proetid and aulacopleurid trilobites of Japan and their palaeogeographical significance

April 2019

April 2019

DOI:10.1002/9781119564249.ch10

In book: Papers from the 6th International Conference on Trilobites and their Relatives (pp.205-232)

Authors:

Chris Stocker

University of Leicester

Mark Williams

University of Leicester

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Trilobites referable to the orders Proetida and Aulacopleurida are geographically wide‐spread in the Silurian and Devonian strata of Japan. They are known from the South Kitakami, Hida‐Gaien and Kurosegawa terranes. Revision of other Japanese trilobite groups, most notably the Illaenidae, Scutelluidae and Phacopidae, has extended the palaeobiogeographical ranges of several Japanese trilobite taxa, but has not signalled conclusive evidence of a consistent palaeogeographical affinity. In part, this may relate to the temporally and spatially fragmented Palaeozoic record in Japan, and perhaps also to the different ecological ranges of the trilobites. Here, we present a taxonomic revision of all previously described proetid and aulacopleurid trilobites from Japan, along with descriptions of new material, which comprises thirteen species (one new: Interproetus mizobuchii n. sp.) within nine genera, with three species described under open nomenclature. These trilobites show an endemic signal at species level, not just between Japan and other East Asian terranes, but also between individual Japanese terranes. This endemicity may be explicable in terms of facies and ecology, rather than simply being a function of geographical isolation.

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The Silurian and Devonian proetid and aulacopleurid

trilobites of Japan and their palaeogeographical signiﬁcance

CHRISTOPHER P. STOCKER, DEREK J. SIVETER, PHILIP D. LANE, MARK WILLIAMS, TATSUO OJI,

GENGO TANAKA, TOSHIFUMI KOMATSU, SIMON WALLIS, DAVID J. SIVETER AND

THIJS R. A. VANDENBROUCKE

Stocker, C.P., Siveter, D.J., Lane, P.D., Williams, M., Oji, T., Tanaka, G., Komatsu, T.,

Wallis, S., Siveter, D.J. & Vandenbroucke, T.R.A. 2019: The Silurian and Devonian

proetid and aulacopleurid trilobites of Japan and their palaeogeographical signiﬁcance.

Fossils and Strata, No. 64, pp. 205–232.

Trilobites referable to the orders Proetida and Aulacopleurida are geographically wide-

spread in the Silurian and Devonian strata of Japan. They are known from the South

Kitakami, Hida-Gaien and Kurosegawa terranes. Revision of other Japanese trilobite

groups, most notably the Illaenidae, Scutelluidae and Phacopidae, has extended the

palaeobiogeographical ranges of several Japanese trilobite taxa, but has not signalled

conclusive evidence of a consistent palaeogeographical afﬁnity. In part, this may relate

to the temporally and spatially fragmented Palaeozoic record in Japan, and perhaps

also to the different ecological ranges of the trilobites. Here, we present a taxonomic

revision of all previously described proetid and aulacopleurid trilobites from Japan,

along with descriptions of new material, which comprises thirteen species (one new:

Interproetus mizobuchii n. sp.) within nine genera, with three species described under

open nomenclature. These trilobites show an endemic signal at species level, not just

between Japan and other East Asian terranes, but also between individual Japanese ter-

ranes. This endemicity may be explicable in terms of facies and ecology, rather than

simply being a function of geographical isolation. □Aulacopleurida, Devonian, Japan,

palaeogeography, Proetida, Silurian.

Christopher P. Stocker [cps10@le.ac.uk], Mark Williams [mri@le.ac.uk], David J. Siveter

[djs@le.ac.uk], School of Geography, Geology and the Environment, University of Leices-

ter, University Road Leicester LE1 7RH, UK; Derek J. Siveter [derek.siveter@oum.ox.a-

c.uk], Oxford University Museum of Natural History, Parks Road Oxford, OX1 3PW,

UK; Philip D. Lane [phil@telychian.co.uk], School of Earth Sciences, Keele University,

Staffordshire, ST5 5BG, UK; Tatsuo Oji [oji@num.nagoya-u.ac.jp], Nagoya University

Museum, Nagoya University, Furo-cho, Chikusa-ku Nagoya 464-8601, Japan; Gengo

Tanaka [gengo@staff.kanazawa-u.ac.jp], Institute of Liberal Arts and Science, Kana-

zawa University, Kakuma-machi Kanazawa City, Ishikawa 920-1192, Japan; Toshifumi

Komatsu [komatsu@sci.kumamoto-u.ac.jp], Faculty of advanced Science and Technol-

ogy, Kumamoto University, 2-39-1, Kurokami Chuo-ku, Kumamoto 860-8555, Japan;

Simon Wallis [swallis@eps.s.u-tokyo.ac.jp], Department of Earth and Planetary Science,

Graduate School of Science, The University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo

113-0033, Japan; Thijs R. A. Vandenbroucke [thijs.vandenbroucke@ugent.be], Depart-

ment of Geology (WE13), Ghent University, 9000 Ghent, Belgium; manuscript received

on 15/05/2018; manuscript accepted on 4/06/2018.

Introduction

Silurian and Devonian marine successions in Japan

comprise those of the South Kitakami Terrane of

north-eastern Honshu, the Hida-Gaien Terrane of

central Honshu and the Kurosegawa Terrane, which

extends from the Kii Peninsula in southwest Honshu

to the islands of Shikoku and Kyushu (Fig. 1). Strata

in each of these terranes contain locally abundant

fossil faunas including brachiopods, cephalopods,

radiolarians, ostracods and trilobites (see Williams

et al. 2014 for an overview).

The trilobite Order Proetida, combined with its

sister group Aulacopleurida, constitutes the most

widely represented and diverse group of trilobites in

Japanese Silurian and Devonian rocks. Previous stud-

ies have described trilobites referable to twelve spe-

cies within eight genera and three in open

nomenclature (Okubo 1951; Kobayashi 1957, 1985,

1988a,b; Kobayashi & Hamada 1974, 1977, 1985a,b,

1986, 1987; Okazaki 1974; Kaneko 2007). In addi-

tion, one new species is described herein and is the

ﬁrst record of its genus from Japan (and indeed east-

ern Asia). These trilobites have, in general, been con-

sidered endemic at the species level, even between

separate Japanese terranes. The recent revision of the

Illaenidae and Scutelluidae of Japan (Holloway &

Lane 1998, 2012, 2016) has nevertheless extended the

palaeobiogeographical ranges of several genera and

species. This study revises the record and taxonomy

of Proetida and Aulacopleurida from Japan. As well

as describing one new species, we re-examine all pre-

viously described species, thereby enabling a compre-

hensive palaeobiogeographical analysis of Japanese

proetid trilobites compared with those of other East

Asian and eastern peri-Gondwanan terranes.

Geological background

Silurian and Devonian fossiliferous sedimentary

rocks of the South Kitakami Terrane occur in the

Hikoroichi and Arisu districts of the Iwate Prefecture

(Fig. 1B). These rocks contain invertebrate fossils

including brachiopods, corals, crinoids, bryozoans

and trilobites, as well as plant fossils and radiolarians.

Silurian trilobites are known from the Wenlock and

Ludlow age Kawauchi Formation and the Llandovery

to Wenlock age Okuhinotsuchi Formation. Although

no proetids or aulacopleurids have previously been

described from these strata, a single proetid

cephalothorax from the Kawauchi Formation is

reported herein, but it has not been formally identi-

ﬁed. In the Devonian, the Nakazato Formation con-

tains a diverse trilobite fauna that includes one

proetid species and additional proetid material noted

in open nomenclature (Kaneko 2007).

Fig. 1. Geographical location of the three Japanese Palaeozoic terranes investigated for trilobites. The dark grey lines on the main map of

Japan (A) denote the approximate position of the South Kitakami (B), Hida-Gaien (C) and Kurosegawa terranes (D,E), and detailed maps

of the outcrops of each are presented in B–E.

206 Stocker et al. FOSSILS AND STRATA

Fossiliferous Silurian and Devonian rocks of the

Hida-Gaien Terrane are found in the Fukuji-Hitoe-

gane area in the Gifu Prefecture and the Kuzuryu

Lake-Upper Ise River area in the Fukui Prefecture

(Fig. 1C). These strata contain conodonts, corals,

radiolarians and trilobites. Strata in the Fukuji-

Hitoegane area have previously yielded one Silurian

proetid species and material that is herein referred to

Coniproteus in open nomenclature, in some instances

tentatively. Most of the Devonian trilobite record of

Japan is from the Hida-Gaien Terrane, including at

least two proetid species and one aulacopleurid

described from the Fukuji Formation and its lateral

equivalent in the Kuzuryu Lake-Upper Ise River

areas, the Kamianama Formation.

In the Kurosegawa Terrane of Shikoku, the

Yokokura Limestone of the Yokokurayama Group,

Yokokurayama, Ochi area, Kochi Prefecture

(Fig. 1D) contains a diverse fossil fauna including

trilobites. The majority of Silurian proetids that

have been described from Japan, with seven spe-

cies, are from the Yokokurayama Group, Fukata

and Gomi formations of the Kochi Prefecture

(Kobayashi & Hamada 1974, 1985a,b, 1986). One

species was described by Kobayashi & Hamada

(1974) from the Okanaru Group (Hirayama et al.

1956) of Higashikawa County, Ehime Prefecture

(Fig. 1D), which corresponds to the Joryu Forma-

tion of the Yokokurayama Group (equivalent to

the lowermost ‘G4 member’of Hamada (1959)).

Trilobites have not been recorded from the overly-

ing Devonian Nakahata and Ochi formations in

that terrane.

In Kyushu, the Kurosegawa Terrane is represented

by the Silurian to Lower Devonian Gionyama For-

mation of Gionyama in the Kuraoka area, Miyazaki

Prefecture (Fig. 1E). It contains a rich invertebrate

fauna of corals, crinoids, bryozoans, stromato-

poroids, brachiopods, trilobites, cephalopods,

bivalves and gastropods (Kido 2010; Kido &

Sugiyama 2011 and references therein). Silurian trilo-

bites, for example Coronocephalus kobayashii, were

described by Hamada (1959) and Kobayashi &

Hamada (1974) from the Gionyama Formation, but

neither proetids nor aulacopleurids were recorded; a

single proetid pygidium is recorded herein. Trilobites

have also been described from the overlying Devo-

nian Naidaijin Formation. Murata et al. (1997), and

subsequently Kaneko (2007), reported two species of

phacopine, and one each of a scutelluid, a lichid, a

calymenid and a proetid, from the Lower Member of

the formation, as well as several species in open

nomenclature. Stocker et al. (2018) described a new

species of phacopine trilobite from the Lower Mem-

ber of the Naidaijin Formation, which combined

with a radiometric age from detrital zircons suggests

a Givetian (Middle Devonian) age for at least part

of the Lower Member (Fig. 2).

Material and methods

The bulk of the material analysed here is from collec-

tions in Japanese museums: Tokyo University

Museum (PA); Kyoto University Museum (KT);

Kochi Prefectural Fossil Museum (KPFM); Yokoku-

rayama Natural Forest Museum, Ochi area, Kochi

Prefecture (YFM); Sakawa Geology Museum, Kochi

Prefecture (SGM, KA); Ofunato City Museum, Iwate

Prefecture (OCM.G); and Nagoya University

Museum (NUM). The numbering system of Kobaya-

shi & Hamada (1977) is complex, and it is not possi-

ble to assign an original number for the specimens

from the Kyoto University Museum collection. This

collection is on loan to the Tokyo University

Museum, and here, we utilize replacement Tokyo

University Museum repository numbers with the

code ‘KT’for these specimens. Silicone moulds and

epoxy replicas of all specimens ﬁgured and cited

herein, as well as one other specimen collected dur-

ing this study, have been deposited in the Oxford

University Museum of Natural History (OUMNH).

The majority of the trilobites were reported by

Okubo (1951), Kobayashi (1957, 1988b), Okazaki

(1974), Kobayashi & Hamada (1974, 1977, 1985b,

1986, 1987) and Kaneko (2007). The specimens of

Kaneko are well localized, with accurate stratigraphi-

cal logs of at least one of the localities and detailed

locality maps for the others. Because the specimens

described by Kobayashi (1957, 1988b) and Kobayashi

& Hamada (1974, 1977, 1985b, 1986, 1987) were

often donated by private collectors, associated local-

ity information is not always precise (Table 1). Fossil

preservation varies between formations, but is gener-

ally poor, with most specimens disarticulated and/or

exfoliated.

Silicone moulds were made from museum speci-

mens using the two-part addition cured polysiloxane

dental putty, Provil Novo Putty. Black epoxy resin

was poured into the moulds, which were then placed

in a pressure chamber at 2 Mbar overnight to harden.

Smaller specimens were coated with gold prior to

scanning electron microscopy (SEM). Casts were

mounted on a black plastic plaque with black plas-

ticine and whitened with ammonium chloride subli-

mate for photography. Digital images were taken

with Leitz ‘Aristophot’apparatus mounted with a

Canon EOS 5D camera and Leica 12 mm Summar

lens. Small specimens were imaged with a Hitachi

S-3600N environmental SEM at Leicester University.

FOSSILS AND STRATA Silurian and Devonian proetid trilobites of Japan 207

Images were processed using Adobe Photoshop CS

2015.5.

Palaeoecology

Proetids inhabited a variety of Silurian and Devonian

lithofacies worldwide, representing a range of envi-

ronments, from shallow to deep marine and includ-

ing carbonates and siliciclastic sedimentary rocks

(e.g. Owens 1973). Hughes & Thomas (2011) sug-

gested that in northern Greenland, proetids utilized

sheltered niches (depressions and cavities) within the

Silurian reefs. Proetids and aulacopleurids have been

interpreted as low-level, epifaunal deposit-feeding

detritivores (Fortey & Owens 1999) and their posses-

sion of a highly conservative natant hypostome (ex-

cept for some highly derived post-Devonian forms)

suggests a particle-feeding habit (Fortey 1990).

Most Japanese proetids are found in shallow water

carbonate lithofacies (Table 2). In the carbonates of the

Silurian Fukata Formation, the associated assemblage

of trilobites includes those from families that are typical

of shallow marine environments such as Scutelluidae,

Illaenidae, Encrinuridae and Lichidae. A similar trilo-

bite fauna co-occurs with proetids in the limestones of

the Silurian part of the Hitoegane Formation in the

Hida-Gaien Terrane. In that terrane too, the proetid-

bearing limestones of the Devonian Fukuji Formation

also record a shallow marine trilobite fauna of

Fig. 2. Generalized lithostratigraphy for Silurian and Devonian strata in the three trilobite-bearing Japanese Palaeozoic terranes investi-

gated here. For the Silurian, ‘lower’denotes Llandovery and Wenlock series, whilst ‘upper’denotes the Ludlow and Pridoli. For the Devo-

nian, Lower, Middle and Upper are formal series. Radiometric ages are from the following sources: Manchuk et al. (2013) for the Yoshiki

Formation, Stocker et al. (2018) for the Naidaijin Formation and Aitchison et al. (1996) for the Gomi Formation.

208 Stocker et al. FOSSILS AND STRATA

Table 1. Silurian and Devonian proetids from Japan, with stratigraphical and geographical provenance and palaeoenvironmental information.

Terrane Formation Chronostrat. Geographical location Locality number Lithofacies Fossils

Proetid/

Aulacopleurid taxa Palaeoenvironment

South

Kitakami

Terrane

Nakazato

Formation

Devonian

(Emsian to

Eifelian

Stage)

Higashizawa, Hikoroichi,

Ofunato City, Iwate

Prefecture, Honshu Island

1. ‘NTL-1’of Kaneko

(2007)

Calcareous

mudstone,

calcareous

sandstone

Corals, brachiopods,

gastropods,

tabulate and rugose

corals, cephalopods

and plants

Dechenella minima Open shelf with

volcaniclastic input

Kawauchi

Formation

Silurian

(Wenlock

Series)

Gyoninzawa, Hikoroichi,

Ofunato City, Iwate

Prefecture, Honshu Island

2. Locality of

Harashinai (1981)

White to grey

limestone

Corals, brachiopods,

bryozoans, bivalves,

cephalopods,

conodonts

Latiproetus?sp.Shallow shelf carbonates

with some terrigenous

input

Hida-Gaien

Terrane

Fukuji

Formation

Devonian

(Lochkovian

to Emsian

Stage)

Fukuji, Okuhida-onsen-

gou, Takayama City, Gifu

Prefecture, Honshu Island

3. ‘Sorayama’of

Kobayashi &

Hamada (1977)

Black-bedded

limestone

Corals, cephalopods,

conodonts,

ostracods,

tentaculitids,

bivalves

Ganinella

fukujiensis,

Ganinella oisensis,

Maurotarion

megalops

Shallow water

carbonates of possible

marginal marine

environment

Kamianama

Formation

Devonian

(Lochkovian

to Emsian

Stage)

Kuzuryu Lake-Upper Ise

River, Fukui Prefecture,

Honshu Island

4. ‘Oise-dani’of

Kobayashi &

Hamada (1977)

Limestone,

argillaceous

limestone

Corals Ganinella oisensis,

Ganinella

fukujiensis

Shallow water

carbonates

Hitoegane

Formation

(upper)

Silurian

(Ludlow

Series)

Hitoegane, Kamitakara-

mura, Yoshiki-gun, Gifu

Prefecture, Honshu Island

5. ‘Loc. 5.’of

Kobayashi &

Hamada (1974)

Banded and

black limestone

Corals, conodonts Ganinella tenuiceps,

Coniproetus sp. A

Carbonate platform

Kurosegawa

Terrane

Naidaijin

Formation

(Lower

Member)

Devonian

(Emsian to

Givetian

Stage)

Tenshuzan, near Tomochi

Town, Shimomashiki

District, Kumamoto

Prefecture, Kyushu Island

6. ‘NDTL-1’of

Kaneko (2007)

Calcareous sandy

mudstone

Corals, crinoids,

brachiopods

Dechenella minima Open shelf

Joryu

Formation

Silurian

(Pridoli

Series)

Okanaru, Seiyo City, Ehime

Prefecture, Shikoku Island

7. ‘Loc. 2.’of

Kobayashi &

Hamada (1974)

Tuffaceous

sandstone

Radiolarians Prantlia bilobus Open shelf with

volcaniclastic input

Fukata

Formation

Silurian

(upper

Wenlock to

lower

Ludlow

Series)

Yokokurayama, Ochi,

Kochi Prefecture, Shikoku

Island

8. ‘Loc 3.’of

Kobayashi &

Hamada (1974)

Limestone and

limestone

conglomerate

Brachiopods,

cephalopods,

corals, crinoids,

conodonts,

stromatoporoids

Interproetus

mizobuchii,

Eremiproetus?

magnicerviculus,

Eremiproetus?

subcarinatus,

Coniproetus

subovalis, Gomiites

granulatus,

Gomiites latiaxis

High-energy fore-reef

Lack of terrigenous

material suggests

isolation from major

landmass

Lists of fossils, lithofacies and chronostratigraphical data are from Williams et al. (2014) and references therein.

FOSSILS AND STRATA Silurian and Devonian proetid trilobites of Japan 209

Table 2. Palaeobiogeographical afﬁnities of Silurian and Devonian proetid species from Japan, China and Australia.

Terrane Formation*Proetid species Relevant biogeographical afﬁnities

Kurosegawa Terrane Fukata Formation Coniproetus subovalis (Kobayashi &

Hamada, 1974)

Different from species of Coniproetus from

other areas

Gomiites granulatus (Kobayashi &

Hamada, 1974)

Gomiites is endemic to the Kurosegawa

Terrane of Japan

Gomiites latiaxis (Kobayashi &

Hamada, 1986)

Gomiites is endemic to the Kurosegawa

Terrane of Japan

Interproetus mizobuchii n. sp. Different from species of Interproetus from

other areas

Eremiproetus?magnicerviculus

(Kobayashi & Hamada, 1974)

Uncertain due to poor preservation

Eremiproetus?subcarinatus

(Kobayashi & Hamada, 1974)

Uncertain due to poor preservation

Hedstroemia sugiharensis (Kobayashi

& Hamada, 1974)

Different from species of Hedstroemia from

other areas

Joryu Formation Latiproetus bilobus (Kobayashi &

Hamada 1974)

Genus common and diverse in South China

Naidaijin Formation Dechenella minima Okubo, 1951 Also occurs in the Nakazato Formation of the

South Kitakami Terrane

Hida-Gaien Terrane Hitoegane Formation Ganinella tenuiceps (Kobayashi &

Hamada, 1987)

Different from species of Ganinella from

other areas

Coniproetus sp. A Different from species of Coniproetus from

other areas

Fukuji Formation Ganinella fukujiensis (Kobayashi &

Hamada, 1977)

Different from species of Ganinella from

other areas

Maurotarion megalops (Kobayashi &

Hamada, 1977)

No links with other Maurotarion species

from other areas

Kamianama Formation Ganinella oisensis (Kobayashi &

Hamada, 1977)

No links with Ganinella species from other

areas

South Kitakami

Terrane

Nakazato Formation Dechenella minima Okubo, 1951 Also occurs in the Naidaijin Formation of the

Kurosegawa Terrane

Melbourne Terrane,

Australia

Mt. Ida Formation,

upper Silurian to

Lower Devonian

Coniproetus sp. nov. of Holloway &

Neil 1982

Different from C. subovalis from the Fukata

Formation of the Kurosegawa Terrane

Benambra Terrane,

Australia

Canberra Group,

Silurian (Wenlock)

Prantlia canberrensis Chatterton &

Campbell, 1980

Considered synonymous with Latiproetus.

Not similar to L. bilobus

Garra Limestone

Formation, Lower

Devonian (upper

Lochkovian to middle

Pragian)

Otarion listron Chatterton, Johnson &

Campbell, 1979

Different from Japanese species of the closely

related genus Maurotarion

Coniproetus irroratus Chatterton,

Johnson & Campbell, 1979

Different from Japanese species of

Coniproetus

Biddabirra Formation,

Lower Devonian

(Lochkovian to

Pragian)

Cyphaspis mcnamari Ebach, 2002 Different from Japanese species of the closely

related genus Maurotarion

Taemas Formation,

Lower Devonian

Cyphaspis dabrowni (Chatterton,

1971)

Different from Japanese species of the closely

related genus Maurotarion

South China Plate Yujiang Formation,

Lower Devonian

Dechenella?liujingensis Zhang, 1974 Different from Dechenella minima found in

the Nakazato Formation of the South

Kitakami Terrane and the Naidaijin

Formation of the Kurosegawa Terrane

Luojiashan Formation,

middle Silurian

Luojiashania meitanensis Zhang, 1974 Similar to Gomiites in cephalic morphology

North China (Sino-

Korean) Plate

Yikewusu Formation,

Middle Devonian

(Eifelian)

Ganinella?auspicata Zhou et al., 2000 Different to Ganinella species found in the

Fukuji and Kamianama formations of the

Hida-Gaien Terrane

Zhusileng Formation,

Middle Devonian

(Emsian)

Paradechenella lunata Zhou et al.,

2000

Paradechenella represented in the Nakazato

Formation (under open nom.)

Otodechenella convexa Zhou et al.,

2000

Otodechenella represented in the Nakazato

Formation (under open nom.)

Basidechenella?exquisita Zhou et al.,

2000

Similar to Dechenella minima of the

Nakazato Formation

Liaoling Terrane,

North China

Zhangjiatun and

Erdagou formations,

middle upper Silurian

Otarion sphaericum (Kuo, 1962) Different from Japanese species of the closely

related genus Maurotarion

Otarion conveximarginatum (Kuo,

1962)

Different from Japanese species of the closely

related genus Maurotarion

*For stratigraphical ages of Japanese formations, see Table 1.

210 Stocker et al. FOSSILS AND STRATA

scutelluids, cheirurids, calymenids, lichids and odonto-

pleurids. The presence of leperditicopid arthropods in a

laminated mudstone in the lower part of the Fukuji For-

mation (Tanaka et al. 2012) suggests a shallow marginal

marine environment. One specimen of the aulacopleurid

Maurotarion megalops (Kobayashi & Hamada, 1977)

has been found alongside a leperditicopid.

In the open shelf mudstones and sandstones of the

Devonian Nakazato Formation in the South Kita-

kami Terrane, trilobites including proetids occur as a

major component of an allochthonous fauna. How-

ever, the original ecological setting of the trilobites

cannot be determined.

Palaeobiogeography

Table 2 summarizes the palaeobiogeographical afﬁ-

nities of Japanese proetids as determined here.

Intra-Japanese terrane palaeobiogeography

Of the thirteen species and nine genera of Japanese

proetids, most are endemic at species level within their

individual terranes, especially so in the Silurian. In

the Devonian, Dechenella minima occurs in the Naka-

zato Formation of the South Kitakami Terrane and at a

comparable stratigraphical level (Eifelian) in the

Naidaijin Formation of the Kurosegawa Terrane

(Table 2). The overall endemic signal of Japanese proe-

tids may reﬂect, in part, lithofacies associations. Most

taxa (e.g. Gomiites and Ganinella)arefoundinshallow

marine carbonates, whilst the lithofacies of the Naka-

zato and Naidaijin formations suggests deeper shelf

environments (Table 1). Fortey (1975) concluded that

in the Early Ordovician of Spitsbergen and North

America (Laurentia), trilobite faunas such as the shal-

low marine ‘illaenid-cheirurid community’were char-

acterized by taxa with a high degree of endemicity,

whereas those faunas in outer shelf settings, such as the

‘nileid community’, had greater potential for dispersal

and were more cosmopolitan. Such a depth-related pat-

tern is also suggested in the Devonian of Japan by

the wide biogeographical afﬁnities of the trilobites in

the Nakazato and Naidaijin formations (Table 2).

Other non-proetid components of the Japanese

early- and mid-Palaeozoic trilobite fauna, such as

scutelluids, illaenids and encrinurids from shallow mar-

ine carbonate lithofacies, have different palaeobiogeo-

graphical afﬁnities to the proetids, and based on the

proposed endemicity of these other groups (see below)

may be more informative to palaeogeography.

Connections with Chinese and peri-

Gondwanan terranes

In contrast to some of the other trilobite groups, the

palaeobiogeographical connections of Japanese proetids

with other regions of East Asia are limited (Fig. 3). For

example, although illaenids and scutelluids (Holloway

& Lane 1998, 2012) from the Silurian Fukata Forma-

tion of the Kurosegawa Terrane show multiple species

Fig. 3. Palaeogeographical map of part of East Asia and adjacent Gondwana during the late Early Devonian (Emsian) at 400 Ma, after Cocks &

Torsvik (2013). E, Enshoo Arc; HUL, Hutag Uul–Songliao; KJB, Khanka-Jiamusu-Bureya; Qi, arcs now in the Qaidam–Qilian Terrane; Sul,

Sulinheer. Bold black lines are subduction zones. According to the ﬁgures in Cocks & Torsvik (2013), there is no signiﬁcant change in the

conﬁguration of these palaeocontinents between the Silurian and Devonian.

FOSSILS AND STRATA Silurian and Devonian proetid trilobites of Japan 211

links with the Australian Benambra Terrane, and

encrinurids show possible links also with Australia

(Strusz 1980), the proetids of the Fukata Formation do

not. Similarly, during the Devonian, palaeobiogeo-

graphical links have been suggested between the lichid

and cheirurid trilobite assemblages of the Fukuji For-

mation of the Hida-Gaien Terrane and the Xiaopu-

tonggou Formation of Shaanxi Province, China (South

China Plate; see Kaneko 2007), but proetids do not

demonstrate the same links. However, the Silurian

upper Hitoegane Formation and the Devonian Fukuji

Formation of the Hida-Gaien Terrane do contain sev-

eral species of the proetid Ganinella,agenusthathas

been recorded in the Silurian and Devonian of Siberia

(Yolkin 1968, 1983), and the Devonian Xipingshan

Formation of Inner Mongolia (Zhou et al. 2000). A

dechenellid fauna has been reported from the Devo-

nian Nakazato Formation of the South Kitakami Ter-

rane by Kaneko (2007), but unlike the phacopids from

the same formation (Kaneko 1990, 2007), these do not

appear to show links with Inner Mongolia faunas

(Zhou et al. 2000).

The apparently limited palaeogeographical dispersal

of Japanese proetids, compared with scutelluids or

encrinurids, might reﬂect ecology and feeding habits.

Proetids in reef limestones of Greenland have been

interpreted as having a cryptic habit as outlined above

(Hughes & Thomas 2011). In contrast, scutelluids, illae-

nids and encrinurids are interpreted to have been more

active predator/scavenger forms (Fortey & Owens

1999). Scutelluids may have been capable of powerful

swimming with their large, ﬂat, ‘paddle-like’pygidia,

with a large surface area and an exceptionally wide dou-

blure (Selwood 1966; Chatterton 1971; Feist & Lerosey-

Aubril 2008), perhaps enabling greater dispersal.

Systematic palaeontology

Remarks. –Morphological terminology for the trilo-

bite exoskeleton follows that of Whittington & Kelly

(1997) and Owens (1973). Ordinal taxonomy is that

of Adrain (2011), whilst the familial-level systematics

of Proetida is that of Ivanova & Owens (in Ivanova

et al. 2009). Synonymy lists only contain entries

where species have been ﬁgured or reassigned, and

not merely cited. For localities, see Table 1.

All of the trilobites occur as disarticulated sclerites.

For those specimens of Kobayashi & Hamada (1974,

1977) that we have been unable to locate, we cannot

always be certain from their illustrations of their degree

of exfoliation, and we have noted this where applicable.

Christopher Stocker, Derek Siveter and Phil Lane are

responsible for the systematic descriptions.

Order Proetida Fortey & Owens, 1975

Family Proetidae Salter, 1864

Subfamily Proetinae Salter, 1864

Genus Coniproetus Alberti, 1966

Type species. –Proetus condensus P

ribyl, 1965 from

the Devonian (Pragian Stage), Czech Republic. By

original designation.

Stratigraphical and geographical range. –Silurian

(Wenlock Series) to Devonian (Emsian Stage), Eur-

ope, North Africa, Australia, North America, Japan.

Coniproetus subovalis (Kobayashi & Hamada, 1974)

Figure 4A, B, D, E

1974 Proetus subovalis Kobayashi and Hamada sp.

nov. Kobayashi & Hamada, pp. 113, 114 (pars),

pl. 12, ﬁg. 1, text-ﬁg. 8A (sic.), (non ﬁg. 2 =

Proetid indet.).

Holotype. –Cranidium (KPFM15188), from Local-

ity 8 (Table 1) (the only specimen).

Diagnosis. –Glabella pyriform; strongly convex

(sag.); furrows absent. Occipital ring with large med-

ian tubercle and well-formed, small subtriangular lat-

eral lobe. Anterior border 10% of glabellar length with

sculpture of strong, parallel terrace ridges.

Fig. 4. Silurian proetids from the Fukata Formation of Yokokurayama, Kochi Prefecture, Shikoku (A–E), and the upper Hitoegane For-

mation, Fukuji-Hitoegane area, Gifu Prefecture (F–T). A,B,D,E,Coniproetus subovalis (Kobayashi & Hamada, 1974), partially exfoliated

holotype incomplete cranidium (KPFM15188) in dorsal stereo, left anterior oblique, left lateral and anterior views. C, proetid indet.,

incomplete right librigena (PA7372), previously tentatively assigned to C. subovalis by Kobayashi & Hamada (1974, p. 113, pl. 12, ﬁg. 1),

dorsal view. F,G–K,P,S,Ganinella tenuiceps (Kobayashi & Hamada, 1987); F, internal mould, paratype left librigena (PA18100), dorsal

view; G-K, partially exfoliated holotype incomplete cranidium (PA18098), left lateral, dorsal stereo, anterior, left anterior oblique and pos-

terior views; P,S, internal mould, juvenile incomplete cranidium (PA18099), dorsal stereo and right anterior oblique views, previously

assigned to Proetus (Coniproetus?) subconicus by Kobayashi & Hamada (1987, p. 138, ﬁgs 1–5a–d). L–O,Coniproetus sp. A., partially exfo-

liated incomplete cranidium (NUM-Fa214), left lateral, dorsal stereo, anterior and left anterior oblique views. Q,R,T, three specimens

tentatively referred to Coniproteus; Q, partially exfoliated pygidium (NUM-Fa217), dorsal stereo view. R, partially exfoliated pygidium

(NUM-Fa216), dorsal stereo view. T, pygidium (NUM-Fa215), dorsal view. Scale bars = 2 mm.

212 Stocker et al. FOSSILS AND STRATA

FOSSILS AND STRATA Silurian and Devonian proetid trilobites of Japan 213

Description. –Cranidium incomplete, strongly con-

vex sagittally, moderately convex transversely. Palpebral

lobe and posterior ﬁxigena not preserved. Glabella 80%

as wide as long with maximum width at 30% length

from posterior; frontal lobe slightly overhanging

preglabellar furrow. Occipital ring 20% as long as

wide, slightly longer than anterior border. Lateral

occipital lobe well-deﬁned and crescentic, approxi-

mately half as wide as long, 20% of occipital width.

Preglabellar ﬁeld short, about 20% as long as ante-

rior border; preglabellar furrow deep. Anterior

border moderately convex.

Glabellar surface with granular sculpture posteri-

orly and on occipital ring anteriorly. Anterior cepha-

lic border with strong, parallel terrace ridges.

Fixigenal ﬁeld smooth.

Discussion. –Kobayashi & Hamada (1974, p. 113)

claimed that the holotype bears many characteristics

in common with Proetus concinnus (Dalman, 1827)

from the Silurian Much Wenlock Formation (Wen-

lock Series) of the UK, but they did not state which

they were. They described and illustrated lateral

glabellar furrows (1974, p. 114, text-ﬁg. 8A) for

which, however, there is no evidence: their S3 furrow

is an artefact (it is asymmetrically placed and in an

incorrect position for a glabellar furrow). They also

questionably assigned an incomplete librigena

(PA7372, their pl. 12, ﬁg. 2) to this species, but the

librigena has a chevron pattern of ﬁne raised ridges,

possibly caecal structures, that are not visible on the

holotype ﬁxigena (Fig. 4C). As a result, we regard

this specimen as a proetid of indeterminate afﬁnity.

Coniproetus sp. A

Figure 4L–O

Material. –Cranidium (NUM-Fa214) from Locality

5 (Table 1).

Description. –Incomplete cranidium strongly (sag.)

and moderately (tr.) convex. Glabella almost as wide

as long, maximum width at approximately 25%

length from posterior margin, across L1; strongly

convex (sag.) with frontal lobe slightly overhanging

preglabellar furrow. Occipital ring 20% as long as

wide, equal in length to anterior border; wide ‘W’in

dorsal outline. Occipital tubercle very poorly pre-

served. Lateral occipital lobe subtriangular, 75% as

long as wide and about 20% of occipital ring width,

divided by shallow, broad intraoccipital furrow.

Occipital furrow deep, moderately wide (exsag.),

increasing in width (exsag.) abaxially; convex

medially. Glabellar furrows effaced; remnants of S1

and S2 indicated by slight indentations on the lat-

eral glabellar margin at 60% and 40% length from

the anterior glabellar margin. Preglabellar ﬁeld very

short; preglabellar furrow moderately deep. Anterior

border convex, long, 12% length of cranidium,

with relatively narrow, deep border furrow.

Palpebral lobe approximately half as wide as long,

with anterior margin in line with approximately

midglabellar length. Anterior facial suture weakly

divergent (36°).

Glabella smooth; anterior border bears coarse ter-

race ridges parallel to the anterior margin; anterior

ﬁxigena with densely packed, large, subcircular pits.

Discussion. –In the only cranidium at hand (NUM-

Fa214), the glabella is partially exfoliated on the left-

hand side (Fig. 4L–O); the remnants of cuticle,

which persist on the right-hand side, lack sculpture.

However, it shows sufﬁcient characters to conﬁdently

assign this specimen to Coniproetus. The glabella is

conical, very convex (sag.) with a steep slope anteri-

orly, and it has a well-developed lateral occipital lobe.

Coniproetus sp. A also possesses some characters

associated with Ganinella, such as the long (sag.) gla-

bella and sculpture of pits on the ﬁxigena, so it may

well represent a transitional form between these two

closely related genera, but there is insufﬁcient mate-

rial to test this hypothesis.

Coniproetus sp. A differs from C. subovalis from

the Fukata Formation of the Kurosegawa Terrane

(Fig. 4A, B, D, E) in the following characters: the gla-

bella is less convex (sag.), longer (sag.), more conical

in dorsal outline, with a wider (trans.) anterior mar-

gin; the occipital ring is wider, with larger (sag.,

trans.) lateral lobe.

An additional three specimens of poorly preserved

pygidia (Fig. 4Q, R, T) have been recovered from the

Silurian part of the Hitoegane Formation (Locality 5,

Table 1), and these have been tentatively assigned to

Coniproetus, based on their subsemicircular pygidial

outline, and weakly developed, short (sag.) pygidial

border; it is uncertain how the pygidia relates to

Coniproetus sp. A.

Genus Ganinella Yolkin, 1968

(=Lophiokephalion Kobayashi, 1988)

Type species. –Dechenella batchatensis Cherny-

sheva, 1951 from the Devonian (Eifelian Stage), Sal-

air, south-western Siberia. By original designation.

Diagnosis. –Glabella elongate and conical to pyri-

form, with a rounded or slightly pointed anterior

margin and three or four pairs of lateral furrows,

214 Stocker et al. FOSSILS AND STRATA

often strongly incised. Genal ridge is present. Pygid-

ium subsemicircular in outline, with eight to twelve

axial rings and ﬁve to eight variably deﬁned ribs.

Sculpture of distinct pitting on ﬁxigenae and librige-

nae; cephalon with granular or tubercular sculpture,

or smooth. (Emended from Yolkin 1968, to include

species described herein).

Discussion. –Owens (1973) considered Ganinella,

Khalﬁnella and Lacunoporaspis to be congeneric;

this was based on the poor material of these genera

originally described by Yolkin (1966) from the

Lower and Middle Devonian of Siberia. We follow

Zhou et al. (2000) in considering Ganinella distinct

from Lacunoporaspis, based on differences in glabel-

lar shape and the often coarse cephalic sculpture.

Relationships between these closely related genera

are difﬁcult to resolve at present and therefore they

are kept separate herein, pending a detailed phylo-

genetic analysis. Lophiokephalion Kobayashi, 1988,

was based on four species from the Devonian Fukuji

Formation (Locality 3, Table 1), the type species

L. antijuba, and L. angustus, L.latipolus and

L. longiconus. We have been unable to locate the

type material of these species (Kobayashi 1988b did

not give a museum repository and indicated only

that they were part of Hamada’s private collection),

and although they are poorly illustrated, it is clear

they belong to Ganinella. The feature Kobayashi

(1988b) described in Lophiokephalion as a librigenal

‘trifurcate keel’is the genal ridge, which is diagnos-

tic of Ganinella.

Stratigraphical and geographical range. –Silurian

(Ludlow Series) to Devonian (Eifelian and ?Frasnian

stages), Russia, North China, Japan.

Ganinella tenuiceps (Kobayashi & Hamada, 1987)

Figure 4F–K, L–P, S

1987 Proetus (Coniproetus)tenuiceps Kobayashi and

Hamada, sp. nov. Kobayashi & Hamada,

p. 136, ﬁgs. 1, 4a–d, ﬁg. 3, 1a, b.

1987 Proetus (Coniproetus?) subconicus Kobayashi

and Hamada, sp. nov. Kobayashi & Hamada,

p. 138, ﬁgs. 1, 5a–d.

Holotype. –Cranidium (PA18098), from Locality 5

(Table 1).

Paratype. –Librigena (PA18100) from Locality 5

(Table 1). The repository number of this specimen

in Kobayashi & Hamada (1987) is incorrectly

recorded as PA18098.

Other material. –Cranidium (PA18099), a juvenile,

from Locality 5 (Table 1) that was originally the

holotype of Proetus (?Coniproetus)subconicus.

Diagnosis. –Glabella coniform, with pointed ante-

rior margin; lateral furrows weakly impressed.

Preglabellar ﬁeld very narrow (sag.); anterior border

broad and convex. Occipital ring moderately long

(sag.), of low relief, with broad, rounded median

tubercle and much reduced lateral lobes. Genal ridge

low and broad. Anterior part of ﬁxigena with distinct

pitting. Anterior border with strong terrace ridges;

anterior ﬁxigena with weakly impressed pitting; cara-

pace otherwise smooth.

Description. –Cranidium incomplete. Glabella

coniform, twice as long as wide, widest at L1 and

65% the width (at δ–δ) of the cranidium, moder-

ately convex (sag.) with steep slope anteriorly. Occip-

ital ring 30% as long as wide, slightly longer than

anterior border, convex (sag.), subelliptical and less

convex (tr.) than the pre-occipital glabella; occipital

tubercle broad and weakly convex. Lateral occipital

lobe very small and crescentic (may be incomplete),

separated by a short, oblique intraoccipital furrow.

Occipital furrow deep, narrow, increasing in length

(exsag.) abaxially. Remnants of lateral glabellar fur-

rows S1 and S2 visible as slight incisions in lateral

margin. Preglabellar ﬁeld <25% the length of ante-

rior border, with deep anterior border furrow. Ante-

rior border broad (sag.), rounded and convex, with

shallow border furrow. Anterior branch of facial

suture weakly divergent; posterior branch moderately

strongly divergent. Palpebral lobe poorly preserved,

narrow, approximately 25% as wide as long, with

anterior margin in line with approximately half

length of the glabella. Lateral border wide, with nar-

row border furrow. Subocular furrow broad, with

narrow ridge. Genal ridge low and broad (tr.).

Glabellar sculpture uncertain; anterior border with

coarse terrace ridges parallel to anterior margin; ﬁxi-

gena with weak pits; librigenal ﬁeld smooth (but

mostly exfoliated); lateral border with coarse, parallel

terrace ridges.

Discussion. –We agree with Kobayashi & Hamada

(1987) that the paratype librigena of G.tenuiceps has

been correctly associated with the holotype, based on

its elongate morphology, broad border and smooth

librigena. The juvenile specimen referred to Proetus

(?Coniproetus)subconicus by Kobayashi & Hamada

(1987) is herein assigned to G. tenuiceps based on

FOSSILS AND STRATA Silurian and Devonian proetid trilobites of Japan 215

the proportions of the glabella. They placed G.tenui-

ceps in Proetus (Coniproetus) Alberti, 1966 based on

its cranidial characteristics, one of which is a well-

developed lateral occipital lobe; but in the single, par-

tial internal mould cranidium available, these are not

well developed: only remnants of cuticle on the fron-

tal lobe and occipital ring being preserved. It is possi-

ble that in the holotype cranidium, the occipital ring

is incompletely known because it appears to be par-

tially sediment-covered, particularly on the left side.

Moreover, glabellar sculpture is unknown. The elon-

gate, conical holotype compares best with Ganinella

species, but the effacement of its furrows and

reduced lateral occipital lobe is unusual, though not

unknown in this genus. From the Devonian of south-

west Siberia, G.schebalinoensis Yolkin, 1968; has a

smooth glabella apparently lacking furrows and

G. tchernyshevae Yolkin, 1968; has a reduced lateral

occipital lobe, which however is not as small as that

of G. tenuiceps. In the overall shape of the glabella

and anterior border, the occipital ring with small lat-

eral lobe, and position and size of palpebral lobe,

G. tenuiceps is similar to Ejinoproetus leprosus Zhou

et al. (2000) from the Emsian and Eifelian of Inner

Mongolia although that species has coarse glabellar

sculpture, weakly incised glabellar furrows and no

median occipital tubercle. Although pygidial charac-

ters are important in diagnosing Ejinoproetus, none

are known in G. tenuiceps.

Ganinella fukujiensis (Kobayashi & Hamada, 1977)

Figure 5A–G, J

1974 Proetus sp. indet. Okazaki, p. 90, pl. 9, ﬁgs 6–9.

1977 Proetus (Coniproetus)fukujiensis Kobayashi

and Hamada, sp. nov. Kobayashi & Hamada,

p. 133, pl. 13, ﬁgs 2–13; text-ﬁg. 3I.

1977 Unguliproetus oisensis Kobayashi and Hamada

sp. nov. Kobayashi & Hamada, p. 133, pl. 13,

ﬁg. 3 (non pl. 12, ﬁgs 1, 2, 4–25, pl. 13. ﬁg.

1, = Ganinella oisensis).

Holotype. –Cranidium (PA8961), from Locality 3

(Table 1).

Paratypes. –Cranidia (PA8962-8964); librigenae

(PA8959, PA8960), pygidia (PA8957, PA8958). All

from Locality 3 (Table 1).

Other material. –Specimens described as Proetus sp.

by Okazaki (1974): cranidium (KT-20160520-38), lib-

rigena (KT-20160520-35) and pygidia (KT-20160520-

02, KT-20160520-35); specimens identiﬁed during this

study: pygidia (NUM-Fa218, NUM-Fa223, NUM-

Fa224,). All from Locality 3 (Table 1). A cranidium

(PA8933) from Locality 4 (Table 1), originally

assigned as a paratype of G. oisensis by Kobayashi &

Hamada 1977, is here assigned to G. fukujiensis.

Diagnosis. –Anterior border 16% length of cranid-

ium. Moderately elongate and subconical glabella,

approximately as long as wide, with weakly incised S1

and S2. Occipital ring wider than pre-occipital glabella

with moderately sized, triangular lateral lobe. Librigena

with short, stout, genal spine. Anterior facial suture

weakly divergent (30°). Fixigena with weak pitting;

cephalon with pustules; pygidium with granules.

Description. –Cephalon 65% as long as wide, mod-

erately convex (sag. and tr.). Cranidium about 10%

wider than long, occupying 60% total width of cepha-

lon at widest point. Glabella moderately convex (sag.

and tr.); subconical; as wide as long, with maximum

width at occipital ring and is 5% of maximum crani-

dial width. Occipital ring 25% as long as wide, 10%

longer than anterior border; occipital tubercle small,

posteriorly positioned. Lateral occipital lobe 80% as

wide as long, 20% width of occipital ring, weakly

depressed, subtriangular and separated by shallow,

broad intraoccipital furrow. Occipital furrow long,

deepening abaxially. Lateral glabellar furrows weakly

incised; S1 50% from anterior of glabella, and 20%

glabellar width, angled posteriorly at about 35°;S2

40% from anterior margin and is about same length as

and parallel to S1; S3 absent. Preglabellar ﬁeld very

short (sag.); preglabellar furrow moderately deep and

Fig. 5. Devonian proetids from the Fukuji Formation, Fukuji-Hitoegane area, Gifu Prefecture (A–G, J), and the Kamianama Formation of

the Kuzuryu Lake-Upper Ise area, Fukui Prefecture (H, I, K–Q). A–G,J,Ganinella fukujiensis (Kobayashi & Hamada, 1977); A, B, partially

exfoliated holotype incomplete cranidium, (PA8961), dorsal stereo and left anterior oblique views; C, internal mould, paratype cranidium

(PA8962), dorsal view; D, partially exfoliated paratype incomplete cranidium, (PA8963), dorsal view; E, partially exfoliated pygidium,

(KT-20160520-02), dorsal view; F, partially exfoliated incomplete cranidium, (PA8933), dorsal view (note well-preserved granular sculp-

ture and S1); G, internal mould, pygidium (KT-20160520-35), dorsal view; J, pygidium, (NUM-Fa218), dorsal stereo view (note well-pre-

served granular sculpture). H,I,K–Q,Ganinella oisensis (Kobayashi & Hamada, 1977); H, internal mould, paratype left librigena attached

to incomplete cranidium, (PA8942), dorsal view; I, paratype right librigena, (PA8943), dorsal view; K, L, partially exfoliated paratype

cranidium (PA8935), left anterior oblique and dorsal views; M, partially exfoliated cranidium, (PA8934), dorsal stereo view; N, partially

exfoliated paratype librigena, (PA8944), dorsal view; O, partially exfoliated paratype pygidium (PA8950), dorsal stereo view; P, partially

exfoliated pygidium (NUM-Fa219), dorsal stereo view (note well-preserved granular sculpture); Q, partially exfoliated paratype juvenile

pygidium (PA8954), dorsal view. Scale bars = 2 mm.

216 Stocker et al. FOSSILS AND STRATA

FOSSILS AND STRATA Silurian and Devonian proetid trilobites of Japan 217

broad (sag.). Anterior border convex, 15% length of

cranidium, 10% shorter than occipital ring, with shal-

low and broad (sag.) anterior border furrow. Palpebral

lobe narrow, an elongate, semi-elliptical platform 30%

as wide as long, occupying 25% length and 7% width

of cranidium, anterior margin in line with anterior of

S2. Cranidial width at δis 60% of maximum. Anterior

facial suture weakly divergent (30°); posterior facial

suture moderately divergent (140°). Eye 40% as wide

as long. Lateral and posterior borders approximately

as broad as anterior border. Librigena 60% as wide as

long and roughly 30% as wide as cranidium. Genal

spine 60% as wide as long, with gently rounded point.

Pygidium 65% as long as wide. Axial furrow deep

and narrow; axis 30% width of pygidium anteriorly,

eight axial rings that become shorter (sag.) posteri-

orly, and terminal piece; ring furrows deep, shallow-

ing posteriorly. Pleural lobe with ﬁve to six pleural

ribs that curve moderately posteriorly, separated by

deep interpleural furrows; anterior three to four ribs

with deep pleural furrows. Axis and pleural lobe of

subequal width anteriorly. Posterior border gently

convex, 10% pygidial length, with a shallow and long

posterior border furrow.

Cephalon bears pustules, and ﬁxigena small shal-

low pits. Pygidium with granules.

Ontogeny. –Cranidia, measured by posterior glabel-

lar width (the only commonly preserved feature), vary

from 3.7 to 7.5 mm; maximum pygidial width ranges

from 4.9 mm to 6.5 mm. Small cranidia (<5mm)

have a relatively broader preglabellar ﬁeld and a trans-

versely wider and longer palpebral lobe than large

specimens. Also, the ﬁxigenal pitting is weakly

expressed in smaller specimens, but this could be a

factor of preservation. The pygidial border becomes

more deﬁned as size increases, but the deﬁnition of

the pleural ribs is variable throughout ontogeny, and

this may similarly be a preservational difference.

Discussion. –Glabellar and pygidial sculpture is

only visible in those specimens with well-preserved

cuticle (e.g. Fig. 5F, J, respectively). Kobayashi &

Hamada (1977, p. 150, text-ﬁg. 3.) showed two pairs

of glabellar furrows in this species. We have also

observed faintly incised S1 and S2 (see Fig. 5D, F;

though in exfoliated specimens, furrows are not visi-

ble: Fig. 5A, C). As a lack of glabellar furrows is diag-

nostic of Coniproetus,Proetus (Coniproetus)

fukujiensis is here reassigned to Ganinella. This is

supported by other characters, including ﬁxigenal

pits and a much more elongate, conical glabella. The

occipital ring in Ganinella fukujiensis is much wider

than in G. tenuiceps, with a more prominent lateral

occipital lobe. G. fukujiensis is similar in its cephalic

characters (other than the border), to Ganinella?aus-

picata Zhou et al. (2000) from the Devonian of Inner

Mongolia, though the pygidium of G.fukujiensis is

different, having fewer axial rings (eight as opposed

to eleven). C. fukujiensis is also similar in glabellar

shape to Ejinoproetus species from the Devonian of

the same region, but Ejinoproetus has a longer and

more subtriangular pygidium with a greater number

of axial rings and pleural ribs.

Ganinella oisensis (Kobayashi & Hamada, 1977)

Figure 5H, I, K–Q

1974 ?Cyrtosymbole sp. Okazaki et al., pl. 1, ﬁgs 5–7.

1977 Unguliproetus oisensis Kobayashi and Hamada,

sp. nov. Kobayashi & Hamada, p. 134, pl. 12,

ﬁgs 1, 2, 4–25, pl. 13, ﬁg. 1; text-ﬁg. 3H (non-

pl. 12, ﬁg. 3 = G. fukujiensis).

Holotype. –Cranidium (PA8932) from Locality 4

(Table 1).

Paratypes. –Cranidia (PA8931, PA8934, PA8935,

PA8937, PA8938); juvenile cranidium (PA8936); libri-

genae (PA8943-8946); librigena attached to partial

cranidium (PA8942); hypostomes (PA8939-8941);

pygidia (PA8947-8956). All from Locality 4 (Table 1).

Other material. –Three pygidia (NUM-Fa219,

NUM-Fa221, and NUM-Fa222) from Locality 3

(Table 1) were identiﬁed during this study.

Diagnosis. –Glabella pyriform, constricted (tr.)

anteriorly and abaxially expanded (tr.) posteriorly.

Occipital furrow deep. Lateral glabellar furrows

weakly incised. Genal ridge low and broad. Moder-

ately long genal spine. Pygidium with seven or eight

distinct pleural ribs and dense granular sculpture.

Description. –Cephalon 80% as long as wide, mod-

erately convex (sag. and tr.). Cranidium about as

long as wide, 65% width of cephalon. Glabella pyri-

form, just over 50% as wide as cranidium, maximum

width at occipital ring. Occipital ring 25% as long as

wide, slightly shorter than anterior border; occipital

tubercle small, lenticular, posteriorly positioned. Lat-

eral occipital lobe 60% as wide as long and 20% the

width of occipital ring, depressed, subtriangular and

separated by moderately shallow, broad intraoccipital

furrow. Occipital furrow long (sag.) and deep. Lateral

glabellar furrows weak, S1 meets axial furrow at 60%

from anterior margin of glabella where it is 30% its

218 Stocker et al. FOSSILS AND STRATA

total width, angled posteriorly at about 25°; S2 meets

axial furrow at 45% length from the anterior margin,

parallel to and about half width of S1; S3 absent.

Preglabellar ﬁeld approximately 50% anterior border

length, with moderately deep preglabellar furrow.

Anterior border weakly convex, 20% cranidial length,

slightly longer than occipital ring; anterior border

furrow moderately shallow and moderately long.

Palpebral lobe a very narrow, elongate, semi-elliptical

platform 20% as wide as long, 25% total length and

5% total width of cranidium; anterior margin in line

with S2. Cranidial width at ais 60% of maximum.

Lateral border at genal angle is about as broad as

anterior border; posterior border 60% of anterior

border length (sag.). Librigena moderately wide, 50%

as wide as long and 60% as wide as cranidium. Genal

ridge low, broad, extends from midwidth of librige-

nal ﬁeld in line with occipital furrow to anterior

ﬁxigena slightly posterior of preglabellar furrow.

Genal spine sharply pointed, moderately long

and narrow, 25% as wide as long; genal angle

approximately 65°.

Hypostome poorly preserved and incomplete, elon-

gate, width across anterior wings approximately 85%

of length. Posterior wing not preserved. Anterior lobe

subparallel sided. Narrow (tr.) maculae, orientated

adaxially at 140°. Posterior lobe reniform and with

moderate independent convexity. Anterior border

poorly preserved, posterior and lateral borders unpre-

served. Middle body with poorly preserved, coarse ter-

race ridges forming a Bertillon pattern.

Pygidium 60% as long as wide. Axial furrow deep

and narrow; axis 35% width of pygidium anteriorly,

with eight axial rings that become shorter posteriorly,

and a short terminal piece; ring furrows are deep,

becoming shallower posteriorly. Pleural lobe formed

of seven or eight ribs curving moderately strongly

backwards, separated by deep interpleural furrows;

anterior three to four ribs with deep pleural furrows,

shallowing posteriorly; ribs 60% longer in anterior

part of pygidium. Posterior border gently convex,

10% of maximum pygidial length, with shallow, long

posterior border furrow.

Glabellar and pygidial sculpture is visible in speci-

mens of this species with well-preserved cuticle (e.g.

Fig. 5K, L, P). Cephalon bears densely packed pus-

tules and ﬁxigenal pits. Pygidium with dense granu-

lar sculpture.

Ontogeny. –Cranidia measured by glabellar width

vary from 1.4 to 6.7 mm; cranidia 3 mm or less have

a relatively broader preglabellar ﬁeld and larger

palpebral lobes. Maximum pygidial width ranges

from 2.0 to 10.3 mm, and the pygidial border is bet-

ter deﬁned as size increases, but the deﬁnition of the

pleural ribs is variable throughout ontogeny, perhaps

due to differences in preservation.

Discussion. –Kobayashi & Hamada (1977) assigned

this species to Unguliproetus but nevertheless

claimed that because in that genus the preglabellar

ﬁeld is typically short and the pleural ﬁeld relatively

distinct, the species was closely related to Coniproe-

tus. However, the species shows the following differ-

ences from Coniproetus: a much more elongate and

pyriform glabellar outline, more incised glabellar fur-

rows and a narrower pygidial axis. Therefore, it is

here assigned to Ganinella.

Ganinella oisensis is similar to Ganinella elegantula

(Yolkin, 1968) from the Devonian of southwest

Siberia,but the latter has a shorter preglabellar ﬁeld

and differs in possessing a longer cephalon, pyriform

glabella with a narrow, rounded anterior margin, dee-

per occipital furrow, better deﬁned and larger occipi-

tal lobe, more incised glabellar furrows, larger eye,

longer preglabellar ﬁeld, much more pronounced

genal ridge, longer genal spine, more convex pygidial

axis and less distinct pygidial pleural ﬁeld.

Genus Gomiites P

ribyl & Vanĕk, 1978

Type species. –Decoroproetus granulatus Kobayashi

& Hamada, 1974 from the Silurian Fukata Formation

of Gomi, Yokokurayama, K^

ochi Prefecture, Shikoku,

Japan (Locality 8, Table 1). By original designation.

Other species. –Gomiites latiaxis (Kobayashi &

Hamada, 1986) from the Fukata Formation of Gomi,

Yokokurayama, Japan (Locality 8, Table 1).

Diagnosis. –Cephalon strongly convex (sag. and tr.);

S1 deep deﬁning a prominent L1; occipital ring with

lateral lobes. Short preglabellar ﬁeld may be present.

Pygidium with ﬁve axial rings and four to ﬁve pleural

ribs with a ﬂat-topped proﬁle; pygidial border short

and weakly convex with broad border furrow. Sculp-

ture of ﬁne to coarse granules on cephalon, thorax

and pygidium, but variable throughout.

Discussion. –P

ribyl & Vanĕk (1978) assigned their

monospeciﬁcGomiites to the Tropidocoryphinae,

which is characterized by a broad preglabellar ﬁeld,

often with tropidial ridge, and an absence of or

reduction in the lateral occipital lobes. Gomiites is

here placed in the Proetinae, based on well-devel-

oped S1 and S2 and lateral occipital lobes, and the

absence of a tropidium. It is most similar to Cypho-

proetus, but differs notably in its strongly sagittally

FOSSILS AND STRATA Silurian and Devonian proetid trilobites of Japan 219

and transversely convex cephalon and the presence

of a pygidial border. Several characters, for example

its ﬂat-topped pygidial ribs, are shared with members

of the Warburgellinae (though it should be noted

that it is difﬁcult to determine the pygidial rib cross-

section in many Gomiites species due to indifferent

preservation), but differences, such as the lack of a

preglabellar ridge or tropidium, suggest Gomiites is

better placed in Proetinae. Gomiites resembles Luoji-

ashania Zhang, 1974 from the Silurian of Sichuan

and Hubei provinces, China, in glabellar outline,

short preglabellar ﬁeld and broad anterior border.

The main differences are that in Luojiashania, L1 is

more poorly deﬁned and the pygidial axis is narrow

and long. There are some similarities between Gomi-

ites and Latiproetus in the deeply incised S1 glabellar

furrow and the broad pygidial border, but the former

is more tuberculate, S1 is deeper and the preglabellar

ﬁeld is much shorter. Several juvenile pygidia

(KA007.6, KA007.13 to KA007.15, KA007.17,

KA007.19, KA007.22, KA-009.2 to KA-009.4, KA-

010.2 to KA-010.4), all from Locality 8 (Table 1), are

herein tentatively assigned to Gomiites.

Stratigraphical and geographical range. –Known

only from the Fukata Formation (Silurian), Japan.

Gomiites granulatus (Kobayashi & Hamada, 1974)

Figure 6A–F, J, M

1974 Decoroproetus granulatus Kobayashi and

Hamada, sp. nov. Kobayashi & Hamada,

pp. 114, 119, pl. 12, ﬁgs 10–13; text-ﬁg. 8G.

1978 Gomiites granulatus (Kobayashi & Hamada,

1974); P

ribyl & Van

ek, p. 179, pl. 2, ﬁgs 6–8.

Holotype. –Cranidium (PA7377), from Locality 8

(Table 1).

Paratypes. –Left librigena (PA7378), thoracopygon

(KPFM15465); pygidium (KPFM15230). All from

Locality 8 (Table 1).

Other material. –Juvenile cranidium (YFM-

1101007), and two juvenile cephalothoraces (KA-

008, KA-010.1), both from Locality 8 (Table 1), iden-

tiﬁed during this study.

Diagnosis. –Anterior border furrow long. Pygidium

with ﬁve axial rings and four pleural ribs; posterior

pygidial border furrow broad and deep, with weakly

convex border. Glabella with coarsely granular sculp-

ture, ﬁner granules on preglabellar ﬁeld and libri-

gena. Thoracic segments with pits on the surface of

axial rings and pleural ribs; moderately ﬁne granules

on anterior two pygidial axial rings and pleural ribs.

Description. –Glabella subquadrate in outline,

rounded frontally, about 70% as wide (at L1) as long

and 70% width of cranidium; moderately strongly

convex (sag. and tr.). Occipital ring 30% as long as

wide, about twice the length (sag.) of anterior border,

with small, triangular lateral occipital lobe (see left

side of holotype, Fig. 6A) and deep intraoccipital fur-

row. S1 meets axial furrow at about midlength of gla-

bella and occupies 20% of total glabellar width,

forming a moderately deep incision trending posteri-

orly at about 150°. S2 meets axial furrow at 25%

glabellar length from anterior margin, and occupies

17% of glabellar width, trending posteriorly at about

135°. Preglabellar ﬁeld short, approximately as long

as anterior border, with deep, short preglabellar fur-

row. Anterior border ﬂat, upturned and 8% of crani-

dial length, with long, deep anterior border furrow

twice as long as anterior border. Anterior facial

suture moderately divergent (33°); indistinct posteri-

orly. Anterior margin of palpebral lobe opposite

anterior of S1. Librigena 62% as wide as long and

approximately 30% as wide as cranidium. Eye 40% as

wide as long; eye socle absent, ocular furrow deep

and broad with a ridge comprising two concentric

rows of granules. Posterior border broader than lat-

eral and anterior borders, and due to carapace exfoli-

ation border furrow narrower than lateral and

anterior border furrows. Genal spine as long as pos-

terior border, slightly wider than lateral border; genal

angle 65°. Holotype cranidium has parts of two exfo-

liated thoracic axial rings attached.

Pygidium semicircular, about twice as wide as

long; moderately convex (tr.). Axial furrow shallow.

Axis 24% of pygidial width anteriorly, with seven

axial rings that become shorter posteriorly, with a

short terminal piece; ring furrows shallow and

Fig. 6. Silurian proetids from the Fukata Formation of Yokokurayama, Kochi Prefecture, Shikoku. A–F,J,M,Gomiites granulatus

(Kobayashi & Hamada, 1974); A, B, F, partially exfoliated holotype incomplete cranidium, (PA7377), dorsal stereo and left anterior obli-

que and anterior views; C, partially exfoliated paratype pygidium with thoracic segments attached, (KPFM15465), dorsal view; D, partially

exfoliated paratype pygidium, (KPFM15230), dorsal view; E, partially exfoliated paratype left librigena, (PA7378), dorsal view; J, M, par-

tially exfoliated juvenile incomplete cranidium (YFM-1101007), anterior and dorsal stereo views. G–I,Gomiites latiaxis (Kobayashi &

Hamada, 1986); G, H, K, L, partially exfoliated holotype incomplete cephalon (PA18078), dorsal stereo, anterior, left lateral and left ante-

rior oblique views; I, paratype pygidium (PA18079), dorsal stereo view. Scale bars = 2 mm.

220 Stocker et al. FOSSILS AND STRATA

narrow. Pleural lobe 33% of pygidial width anteri-

orly, with four, ﬂat-topped ribs which curve gently

backward, more strongly so and shorter posteriorly.

Pleural furrows deep, shallowing anteriorly;

interpleural furrows indistinct. Pleural lobe 20%

wider than axis anteriorly. Posterior border with low

convexity is 8% of pygidial length, with deep poste-

rior border furrow almost twice as long.

FOSSILS AND STRATA Silurian and Devonian proetid trilobites of Japan 221

Glabella is coarsely granulose; preglabellar ﬁeld with

ﬁner granules; ﬁne granules on axial rings and thoracic

pleurae and least ﬁrst two pygidial pleural ribs.

Ontogeny. –A juvenile cephalothorax is assigned to

this species based on similarities with adults in the

glabellar outline, glabellar furrows, broad anterior

border furrow, ﬂat anterior border and coarse tuber-

culation on the glabella and preglabellar ﬁeld. The

major difference between juvenile and adult is in the

preglabellar ﬁeld length, which is relatively shorter in

mature individuals of G.granulatus. However, this

feature has been shown to undergo reduction during

ontogeny in different proetid groups (e.g. Cyrtosym-

bolinae; Lerosey-Aubril & Feist 2005).

Discussion. –Kobayashi & Hamada (1974) com-

pared Decoroproetus granulatus to the type species of

Decoroproetus:Decoroproetus decorus (Barrande,

1846) from the Lite

n Formation (Wenlock Series) of

the Prague District and claimed that the ‘frontal bor-

der’of their new Japanese species was considerably

broader and the pygidium shorter with a broader

and longer axis. Also, they suggested a tropidial ridge

was present, but our examination indicates it is

absent. Further, they indicated that the preglabellar

ﬁeld in D. granulatus is divided into a smooth inner

and a granulose outer band separated by a furrow,

but this difference simply represents exfoliation.

P

ribyl & Vanĕk (1978) described the same features as

Kobayashi & Hamada (1974), but they did not ﬁgure

the holotype, and their illustrations appear to be bor-

rowed from that paper. Nevertheless, they reassigned

D.granulatus, making it the type species of their

new genus Gomiites.

Kobayashi & Hamada (1974) described only the

S2 furrow in D.granulatus, yet in their text ﬁgure,

the posterior part of the glabella is straight-sided with

no furrow. There is, however, evidence for an S1 on

the right side of the holotype (Fig. 6A), although it is

poorly preserved. D. granulatus is maintained in

Gomiites based on its deep, well-developed lateral

occipital lobe, the absence of a tropidium and pygi-

dial ribs with a ﬂat-topped proﬁle. It is similar to

G. latiaxis in its deeply incised S1 glabellar furrow;

sagittally narrow preglabellar ﬁeld with granular

sculpture; sagittally wide anterior border furrow;

small eye; broad posterior pygidial border furrow;

and ﬂat-topped pygidial pleural ribs. Differences in

G. granulatus from G. latiaxis include a less sagit-

tally and transversely convex cephalon, better-

rounded glabella and better developed S2.

A juvenile specimen (Fig. 6J, M) has been assigned

to this species based on its glabellar outline, deeply

incised and diagonal S1, weakly incised S2, position

of the palpebral lobe, deep preglabellar furrow,

glabellar and preglabellar ﬁeld sculpture of coarse

granules. The only major differences are that this

juvenile shows a less convex glabella and a larger

palpebral lobe. Also, there is a poorly preserved med-

ian occipital tubercle on this specimen, which is not

preserved in any other Gomiites specimen, probably

due to incomplete cuticle preservation.

Gomiites latiaxis (Kobayashi & Hamada, 1986)

Figure 6G–I, K, L

1986 Cyphoproetus latiaxis Kobayashi and Hamada,

sp. nov. Kobayashi & Hamada, p. 453, pl. 91,

ﬁgs 1a–g, 2a–c.

Holotype. –Cephalon (PA18078), from Locality 8

(Table 1).

Paratypes. –Pygidium (PA18079), from Locality 8

(Table 1).

Diagnosis. –Cephalon with wide, subtrapezoidal

glabella with deep, short S1 furrow that shallows

abaxially and posteriorly. Small, triangular lateral

occipital lobe. Very small eye situated at midglabellar

length. Small pygidium with long, broad, concave

posterior border furrow; pygidial pleural ribs with

ﬂat-topped proﬁle. Cephalon with coarse granules.

Description. –Cephalon 65% as long as wide,

strongly convex (sag. and tr.). Cranidium approxi-

mately as long as wide, 70% width of cephalon, maxi-

mum at ω. Glabella subtrapezoidal, 70% width of

cranidium, 55% as long as wide with maximum

width across occipital ring, tapers gently forwards to

a weakly convex, subtransverse anterior margin.

Occipital ring 35% as long as wide, about twice as

long as anterior border; the exfoliated cuticle reveals

a striated doublure of the median lobe (Fig. 6G, K,

L); lateral lobe small, triangular, anteriorly sited,

comprising 20% of width of ring, deﬁned by deep

intraoccipital furrow. S1 deep and wide medially,

shallows abaxially and posteriorly, meets axial furrow

at midglabellar length, occupies 30% of glabellar

width, angled posteriorly at 35°; S2 weakly incised,

30% from anterior margin of glabella, occupying

18% of glabellar width, subparallel to S1. Narrow

preglabellar ﬁeld 50% length of anterior border, with

deep, narrow preglabellar furrow. Anterior border

ﬂat, narrow, approximately 10% length of cranidium,

with shallow, moderately broad anterior border fur-

row, approximately half as broad as anterior border.

222 Stocker et al. FOSSILS AND STRATA

Cranidial width at δis 83% of maximum. Anterior

facial suture strongly divergent (125°). Palpebral lobe

semi-elliptical, very small, as long as lateral occipital

lobe, with anterior margin in line with anterior of S2;

eye very small, eye socle narrow and convex (tr.).

Lateral and anterior borders similar, posterior border

unpreserved; posterior border furrow broad and

deep.

Pygidium semi-elliptical in outline, about half as

long as wide. Axial furrow shallow; axis approximately

35% pygidial width anteriorly, comprises ﬁve axial

rings and short terminal piece 10% of axial length; ring

furrows moderately deep, shallowing posteriorly. Pleu-

ral lobe with ﬁve ribs, straight, separated by deep pleu-

ral furrows; interpleural furrows moderately deep; ribs

with ﬂat-topped proﬁle. Pleural lobe 10% narrower

than axis at maximum width. Posterior border weakly

convex, 10% of pygidial length; border furrow long

and broad, slightly longer than border.

Cephalon with coarse granules; pygidial axis and

ﬁrst two pleural ribs with sparse granules.

Discussion. –Kobayashi & Hamada (1986, p. 454)

claimed that this species belonged to ‘aCyphoproetus

group with a narrow preglabellar area and granulose

sculpture, as in Cyphoproetus strabismus, but with

coarser granulation, a broader cranidium and gla-

bella, and smaller eyes’. The holotype of C. strabis-

mus Owens, 1973 (Owens 1973, pl. 6, ﬁg. 15a–d),

from the Lite

n Formation (Wenlock Series) of the

Czech Republic, has a much broader preglabellar

ﬁeld (although the specimen of Owens 1973, pl. 6,

ﬁg. 13 has a narrow preglabellar ﬁeld similar to that

in G. latiaxis), and the lateral occipital lobe is much

larger in C. strabismus.G. latiaxis is similar to

Cyphoproetus facetus Tripp, 1954, from the Upper

Ordovician Craighead Limestone Formation, Girvan,

Scotland, in its narrow preglabellar ﬁeld and small

lateral occipital lobe. However, the cephalon of G.la-

tiaxis is signiﬁcantly more convex than that of any

Cyphoproetus species.

G. latiaxis is also similar to the type species of

Gomiites,G. granulatus, in its deeply incised S1

glabellar furrow, short preglabellar ﬁeld with granu-

lar sculpture, long anterior border furrow, small eye

and broad posterior border furrow. Differences from

G.granulatus include a more sagittally and trans-

versely convex cephalon, more ﬂattened anterior

margin to the glabella, the outline of which is con-

stricted opposite the anterior margin of the eye. The

possible eye socle that Kobayashi & Hamada (1986)

described may be an indeterminate cuticle fragment,

with this feature being the narrow indistinct ridge

that they described behind the left eye.

Subfamily Crassiproetinae Osm

olska, 1970

Genus Hedstroemia P

ribyl & Vanĕk, 1978

Type species. –Proetus delicatus Hedstr€

om, 1923,

from the Halla Formation, Silurian (Wenlock Series),

Horsne Canal, Gotland, Sweden. By original designa-

tion.

Stratigraphical and geographical range. –Silurian

(Llandovery to Pridoli series), Europe, North Amer-

ica, central Asia, Australia and Japan.

Hedstroemia sugiharensis (Kobayashi & Hamada,

1974)

Figure 7A–C

1974 Proetus (Gerastos)sugiharensis Kobayashi and

Hamada, sp. nov. Kobayashi & Hamada,

p. 116, pl. 12, ﬁgs 5, 6; text-ﬁg. 8C.

1985 Proetus (Gerastos)sugiharensis Kobayashi &

Hamada, 1974; Kobayashi & Hamada, p. 208,

pl. 29, ﬁg. 1a-c.

1990 Hedstroemia?sugiharensis (Kobayashi &

Hamada, 1974); L€

utke, p. 49.

2006 Hedstroemia sugiharensis (Kobayashi &

Hamada, 1974); Owens, p. 126, ﬁg. 5.4.

Holotype. –Pygidium (PA7375), from Locality 8

(Table 1).

Paratypes. –Pygidium (KPFM809), from Locality 8

(Table 1).

Other material. –Pygidium ﬁgured in Kobayashi &

Hamada (1985b, pl. 29, ﬁg. 1), from Locality 8

(Table 1). No repository number was given for this

specimen.

Diagnosis (emended from Owens 2006). –Pygid-

ium strongly convex (tr.) with long (sag.), convex

border and broad, gently tapering axis with ten rings

plus terminal piece. Pleural lobe with seven ribs with

a scalloped proﬁle and distinct pleural furrows. Pygi-

dial sculpture ﬁnely granulose.

Description. –Pygidium 75% as long as wide,

strongly convex (sag. and tr.). Axial furrow moder-

ately shallow and narrow; axis with seven rings,

45% of pygidial width anteriorly, becoming

FOSSILS AND STRATA Silurian and Devonian proetid trilobites of Japan 223

gradually less well-deﬁned posteriorly, with a poorly

deﬁned terminal piece; ring furrows shallow and

narrow, becoming less distinct posteriorly. Pleural

lobe strongly convex (tr.), comprising seven ribs that

curve moderately strongly backwards, separated by

distinct pleural furrows that become poorly deﬁned

posteriorly; interpleural furrows weaker, broaden

(sag.) slightly abaxially and terminate at border fur-

row; ribs with scalloped proﬁle; postaxial ﬁeld is 6%

pygidial length (sag.); border strongly convex with

moderately shallow and moderately broad border

furrow. Pygidium bears ﬁne granules on pleural

ribs.

Discussion. –In referring this species to Proetus

(Gerastos), Kobayashi & Hamada (1974) indicated

that its pygidium had ‘about 10’axial rings, which

however exceeds that in the diagnosis for Gerastos

(a maximum of eight). In addition, there are no

prominent subparallel terrace ridges on the pygidial

border, and no evidence of single rows of small

perforations there as noted in Gerastos by Adrain

(1997). The holotype pygidium however has only

seven rings, which places it within the diagnosis of

Hedstroemia P

ribyl & Vanĕk, 1978. Other charac-

ters in line with this generic position include the

nine pleural ribs with well-deﬁned pleural and

interpleural furrows, the clavate swellings at the

distal ends of pleural ribs and a distinct pygidial

border. Therefore, we agree with L€

utke (1990) and

Owens (2006) that this species better belongs in

Hedstroemia.

Subfamily Cornuproetinae Richter et al. in

Moore, 1959

Genus Interproetus



Snajdr, 1977

Type species. –Proetus intermedius Barrande, 1846,

p. 63, from the Kopanina Formation (Silurian,

Ludlow Series), Dlouh

a Hora, Prague Basin, Czech

Republic. By original designation.

Stratigraphical and geographical range. –Silurian

(Wenlock and Ludlow series), Ireland, Czech Repub-

lic, Uzbekistan and Japan.

Interproetus mizobuchii n. sp.

Figure 7D–H, K

Derivation of name. –Named for Mr Mizobuchi,

Curator of Sakawa Geology Museum, Kochi Prefec-

ture, Shikoku, collector of the holotype.

Holotype. –A cephalon (SGM1301), from Locality

8 (Table 1).

Other material. –Cranidium (KA-019) and pygid-

ium (KA-002) from Locality 8 (Table 1), identiﬁed

during this study.

Diagnosis. –Cephalon with moderately long (3 mm)

genal spines. Cranidium narrow, with short palpebral

lobe. Glabella with very long occipital ring and weakly

impressed lateral furrows. Anterior border long and

convex with short, deep border furrow. Preglabellar

ﬁeld less than 50% length of anterior border. Eye large.

Description. –Cephalon moderately strongly convex

(sag. and tr.). Cranidium 15% longer than wide and

75% width of cephalon, with 65% cranidial width at δ

and maximum width at ω. Glabella weakly convex (sag.

and tr.), subquadrate, 75% as long as wide with maxi-

mum width across anterior of occipital ring and 55%

width of cranidium; Occipital ring 25% as long as wide,

twice as long as anterior border; occipital tubercle small,

anteriorly placed, weak; lateral occipital lobe small and

weak. Lateral glabellar furrows weakly incised. S1 meets

axial furrow at midglabellar length and expands adaxi-

ally posteriorly to a point opposite posterior margin of

Fig. 7. Silurian proetids from the Fukata Formation (A–K, -N), Nakazato Formation (M), Gionyama Formation (P), and Kawauchi Forma-

tion (R) and a Devonian aulacopleurid from the Fukuji Formation (L, O, Q, S). A–C,Hedstroemia sugiharensis (Kobayashi & Hamada,

1974), holotype pygidium, (PA7375), dorsal, posterior and left lateral views. D–H,Interproetus mizobuchii n. sp.; D-G,holotype,

(SGM1301), right anterior oblique, dorsal stereo, anterior and right lateral views, H, incomplete cranidium (KA-019), dorsal view. I,J,

Eremiproetus?subcarinatus (Kobayashi & Hamada, 1974); I, partially exfoliated holotype incomplete cranidium (PA7373), dorsal view; J, par-

tially exfoliated paratype incomplete cranidium (PA07374), dorsal view. K, Interproetus mizobuchii n. sp., incomplete pygidium (KA-002),

dorsal view. L,O,Q,S,Maurotarion megalops (Kobayashi & Hamada, 1977); L, internal mould, paratype cranidium (KT-20160520-03C),

dorsal view; O, internal mould, holotype cephalon (KT-20160520-03A), dorsal view; Q, cephalon, silicone cast of external mould, (OUMNH

DY.15), dorsal stereo view; S, partially exfoliated paratype thoracopygon (KT-20160520-03B), dorsal view. M,Dechenella minima (Okubo,

1951), holotype cranidium (PA08006), dorsal stereo view. N,Eremiproetus?magnicerviculus (Kobayashi & Hamada, 1974), internal mould,

holotype cranidium, (PA7376), dorsal view. P, partially exfoliated pygidium possibly referable to Latiproetus (NUM-Fa220), dorsal view. R,

incomplete cephalothorax possibly referable to Latiproetus (OCM.G.000647), dorsal view. Scale bars = 2 mm.

224 Stocker et al. FOSSILS AND STRATA

FOSSILS AND STRATA Silurian and Devonian proetid trilobites of Japan 225

eye; S2 meets axial furrow 30% from anterior glabella

margin, and S3 15% from anterior margin. Preglabellar

ﬁeld <50% length of anterior border, with short, moder-

ately shallow preglabellar furrow. Anterior border

strongly convex (sag.), 10% of cranidial length, 50% as

long as occipital ring, with deep, broad anterior border

furrow. Palpebral lobe very narrow and semi-elliptical,

posteriorly placed, with posterior margin adjacent to

posterior of L1, 25% as wide as long and occupying 35%

length and 7% width of cranidium. Facial suture diver-

gent anteriorly at 40°and divergent posteriorly at 125°.

Librigena narrow, 20% as wide as long. Lateral and pos-

terior borders approximately as broad as the anterior

border. Genal spine 15% as wide as long. Eye large; eye

socle narrow (tr.) with deep, narrow (tr.) furrow and

broader subocular furrow lacking an abaxial ridge.

Sculpture of granules on glabella; ﬁne terrace

ridges on anterior border.

Discussion. –This species is assigned here to Inter-

proetus based on its subquadrate glabella, long occipi-

tal ring with reduced lateral lobe and moderately long

genal spines. The genus is commonly represented in

Europe, in particular the Czech Republic, with

numerous species described from Wenlock to Ludlow

strata (



Snajdr 1980). The only other non-European

occurrence of this genus is Interproetus pentaxus Iva-

nova & Owens, 2009 (in Ivanova et al. 2009) from

Uzbekistan, which differs from I. mizobuchii in its

shorter glabella, narrower occipital ring, wider and

more rounded adaxially S1, slightly longer genal spine

and coarser terrace ridges on the cephalic border.

Subfamily Eremiproetinae Alberti, 1967

Genus Eremiproetus Richter & Richter, 1919

Type species. –Proetus eremita Barrande, 1852 from

the Devonian (Eifelian Stage), of the Czech Republic.

By original designation.

Stratigraphical and geographical range. –Ordovi-

cian to Devonian, Sweden, Czech Republic, Germany,

Morocco, and possibly Inner Mongolia and Japan.

Eremiproetus? subcarinatus (Kobayashi & Hamada,

1974)

Figure 7I, J

1974 Proetus (Gerastos)subcarinatus Kobayashi and

Hamada, sp. nov. Kobayashi & Hamada, 1974,

p. 115, pl. 12, ﬁgs 3, 4; text-ﬁg. 8D.

Holotype. –Cranidium (PA7373), from Locality 8

(Table 1).

Paratypes. –Cranidium (PA07374), from Locality 8

(Table 1).

Diagnosis. –Cranidium with wide subquadrate

glabella, long (sag.) occipital ring, long (sag.)

convex anterior border and deep anterior border

furrow.

Description. –Cranidium incomplete. Glabella

weakly convex (sag. and tr.), subquadrate with

rounded anterior margin, 70% as wide as long

with maximum width across L1. Occipital ring

25% length of glabella; weakly convex (sag. and

tr.). Occipital tubercle weak and anteriorly placed;

occipital lobe absent; occipital furrow shallow and

broad. Glabellar furrows effaced except for very

poorly deﬁned S1 marked by a slight impression

in the lateral glabellar margin. Preglabellar ﬁeld

very short, with moderately deep preglabellar fur-

row. Anterior border longer medially, representing

10% length of the cranidium, with deep furrow.

Fixigenae absent from both specimens, except for

slight remnant on left side of holotype at just

posterior of midlength. Carapace smooth.

Discussion. –Kobayashi & Hamada (1974) based

this species on two incomplete specimens that are

mostly internal moulds with otherwise poorly pre-

served cuticle. The holotype is a small juvenile

with an incompletely preserved occipital ring; the

paratype has a glabella with the same outline and

a similarly short (sag.) preglabellar ﬁeld and long

border. Kobayashi & Hamada (1974) compared

E.?subcarinatus to the type species of Gerastos,

whilst indicating that in the former the glabella is

larger, less convex, subparallel sided and subcari-

nate axially, and lacks lateral furrows and with a

longer occipital ring. The weak convexity of the

glabella is possibly a result of tectonic deforma-

tion, this also leading to a subcarinate appear-

ance. However, the long (sag. exsag.) occipital

ring, glabellar shape and longer median anterior

border are all characters found in Eremiproetus.

Nevertheless, there is no occipital spine preserved,

and without a pygidium, it is difﬁcult to make a

ﬁrm generic assignation. This Japanese species

does not belong to Gerastos but, based on the

characters available, is closer to Eremiproetus and

we tentatively assign it to that genus. In compar-

ison with E.?magnicerviculus, which is also from

the Fukata Formation of Shikoku, the glabella of

226 Stocker et al. FOSSILS AND STRATA

E.?subcarinatus is much less convex and margin-

ally wider, with a shorter occipital ring.

Eremiproetus? magnicerviculus (Kobayashi &

Hamada, 1974)

Figure 7N

1974 Proetus (Bohemiproetus)magnicerviculus

Kobayashi and Hamada, sp. nov. Kobayashi &

Hamada, p. 117, pl. 12, ﬁg. 7; text-ﬁg. 8E.

Holotype. –Incomplete cranidium (PA7376), from

Locality 8 (Table 1) (the only specimen).

Diagnosis. –Glabella with very long occipital ring,

40% of its length and with both median and posterior

median tubercle. Anterior border slightly inﬂated

(sag.) medially and occupies 10% of length of cranid-

ium.

Description. –Glabella subovate with straight lateral

margins, moderately convex (sag. and tr.), 70% as

wide as long with maximum width posteriorly. Long

occipital ring, moderately convex (sag. and tr.) with a

shallow, gentle slope on the anterior margin to form

a long occipital furrow; median tubercle small and

central; another tubercle may be present on the med-

ian posterior margin; occipital lobe absent. S1 very

weak, other glabellar furrows effaced. Anterior bor-

der furrow moderately deep and short. Preglabellar

ﬁeld short, approximately 25% as long as anterior

border, with short, shallow preglabellar furrow.

Discussion. –The diagnosis and description are

based only on the holotype –an internal mould of an

incomplete cranidium. Kobayashi & Hamada (1974)

placed E. magnicerviculus in Bohemiproetus Pillet,

1969, while Owens (1973) considered Bohemiproetus

to be a junior synonym of Proetus (Coniproetus)

Alberti, 1966; which has subsequently been elevated

to generic status (



Snajdr 1980).

E.?magnicerviculus differs from Coniproetus spe-

cies in that the glabella is roughly parallel sided and

subquadrate, the lateral furrows are not effaced, S1 is

poorly expressed and isolates a small L1 and the

occipital ring is very long and bears a median tuber-

cle anteriorly. Based on its subquadrate glabella with

long occipital ring, and medially long anterior bor-

der, E.?magnicerviculus is very similar to Eremiproe-

tus species, but it is not clear in the Japanese

specimen if there is an occipital spine at the poste-

rior, and it is not possible to conﬁdently place it in

this genus.

In comparison with E.?subcarinatus, from the

same formation, the glabella of E.?magnicerviculus is

much less convex and marginally wider, with a

shorter occipital ring.

Subfamily Dechenellinae P

ribyl, 1946

Genus Dechenella Kayser, 1880

Type species. –Phillipsia verneuili Barrande, 1852

from the Devonian (Givetian) of Germany. By origi-

nal designation.

Stratigraphical and geographical range. –Devonian

(Emsian to Givetian stages), Europe, North America,

and Morocco.

Dechenella minima Okubo, 1951

Figure 7M

1951 Dechenella minima, sp. nov. Okubo, p. 136, pl.

1, ﬁg. 6a–c.

1957 Dechenella (Dechenella)minima Okubo;

Kobayashi, p. 7, pl. 1, ﬁgs 1a, b, 2a, b.

1977 Dechenella (Dechenella)minima Okubo;

Kobayashi & Hamada, p. 143, pl. 8, ﬁg. 8; text-

ﬁg 3F.

2007 Dechenella minima Okubo, 1951; Kaneko, pl.

3, ﬁgs 12, 13.

Holotype. –Cranidium (PA08006), from Locality 1

(Table 1).

Other material. –A pygidium ﬁgured by Kaneko

(2007, pl. 3, ﬁg. 13) from Locality 1 (Table 1).

Diagnosis. –Glabella short, subtriangular, strongly

convex (sag.) with deeply incised S1 and S2; L1 and

L2 independently convex. Preglabellar ﬁeld short,

anterior border long. Pygidium with narrow axis of

twelve rings, and nine pleural ribs, interpleural fur-

rows lacking.

Description. –Cranidiumalmostaslongaswide,

moderately convex (sag. and tr.). Glabella moderately

convex (tr.); 15% longer than wide, constricted in ante-

rior half with maximum width over L1; 70% length

and 75% width of cranidium. Occipital ring weak and

low;20%aslongaswide,occupying15%glabellar

FOSSILS AND STRATA Silurian and Devonian proetid trilobites of Japan 227

length and 65% glabellar width; median third slightly

wider than lateral third, median occipital tubercle ante-

riorly placed; lateral occipital lobe absent. Lateral

glabellar lobes have distinct independent convexity,

separated by furrows trending adaxially forwards at

about 45°. S1 meets axial furrow at approximately 70%

from anterior glabellar margin, and occupies 40% of

glabellar width, meeting occipital furrow at 30% of its

width; S2 meets axial furrow at 55% length from ante-

rior margin and occupies 25% of glabellar width; S3

meets axial furrow at 40% length from anterior margin

and occupies 5% of glabellar width. Preglabellar ﬁeld

absent. Anterior border long, convex (sag.), strongly

upturned and 15% cranidial length, with long shallow

anterior border furrow. Palpebral lobe large, 45% as

wide as long, occupying 25% cranidial length and 10%

cranidial width; posterior margin adjacent to posterior

of L1.

Pygidium conical, long and narrow, 15% longer

than wide. Axis long and narrow, 40% pygidial width

anteriorly, comprising twelve (possibly thirteen) axial

rings separated by narrow, deep ring furrows. Pleural

lobe about 40% of pygidial width anteriorly; much

wider than axis, with at least nine ribs separated by

narrow, deep interpleural furrows; ribs narrow, lack-

ing pleural furrows.

Carapace lacks sculpture.

Discussion. –In the only ﬁgured pygidium (Kaneko

2007, pl. 3, ﬁg. 13), it is impossible to count the

number of rings and ribs and to determine the pres-

ence or absence of a posterior border. This pygid-

ium may be distorted, as it is unusually narrow and

elongate, with a very narrow axis; we have been

unable to locate this specimen in any museum col-

lection. D. minima resembles Dechenella ormistoni

Yolkin, 1979 from the Devonian of south-west

Siberia, in its short glabella with deeply incised lat-

eral furrows, but D. ormistoni has coarse granular

sculpture and a more convex anterior border with a

deeper border furrow. The broad, ﬂat anterior bor-

der with a broad, shallow anterior border furrow of

D.minima is a diagnostic character of Basidech-

enella Yolkin, 1968, and in this character, it espe-

cially resembles Basidechenella arctica Maximova,

1977, but in the latter species, the occipital lobe is

well developed, and the frontal lobe is more elon-

gate. Of the dechenellids described by Zhou et al.

(2000) from the Devonian of Inner Mongolia, the

most similar to D. minima is Basidechenella?exqui-

sita which has a glabella with a similar dorsal out-

line, but is much less convex, with poorly incised

furrows; in addition, the anterior cephalic border of

B.?exquisita is much longer, the lateral occipital

lobe better developed and the pygidium much

shorter and wider.

Subfamily Warburgellinae Owens, 1973

Genus Latiproetus Lu, 1962

Type species. –Proetus latilimbatus Grabau, 1924;

from the Silurian of western Hubei, China (see Lu

1962).

Stratigraphical and geographical range. –Silurian

(Llandovery to Ludlow series), China, Australia,

Canada.

Discussion. –We follow Sun (1990) in considering

Latiproetus distinct from Astroproetus (see Lane &

Wu 2002), based on the sigmoidal proﬁle of the

preglabellar ﬁeld and differences in lateral occipital

lobes. A single pygidium (Fig. 7P) from the Sil-

urian Gionyama Formation of the Kurosegawa Ter-

rane (Locality 7) may belong to Latiproetus.A

single, incomplete cephalothorax (Fig. 7R) from the

Silurian Kawauchi Formation of the South Kita-

kami Terrane (Locality 2, Table 1) is similar to

Latiproetus in the shape of the glabella and the

deeply incised S1. Furthermore, it is possible that

some juvenile pygidia (KA-006.1 –KA-006.5, KA-

007.1, KA-007.5, KA-007.7, KA-007.18, KA009.5

and KA-010.1) from the Silurian Fukata Formation

(Locality 8) may belong to Latiproetus, particularly

those lacking a broad pygidial border furrow and

border.

Latiproetus bilobus (Kobayashi & Hamada, 1974)

1974 Prantlia biloba Kobayashi and Hamada, sp.

nov. Kobayashi & Hamada, pp. 114, 118, pl.

12, ﬁgs 8, 9; text-ﬁg. 8F.

1985b Latiproetus biloba (Kobayashi & Hamada, 1974);

Kobayashi, p. 422.

Holotype. –Cranidium (OCU PA0006), from

Locality 7 (Table 1).

Paratype. –Pygidium (OCU PA0002), from Local-

ity 7 (Table 1).

Diagnosis. –Glabella with deeply incised S1;

preglabellar ﬁeld and anterior border short.

228 Stocker et al. FOSSILS AND STRATA

Pygidium narrow, subtriangular, with anterior two

ribs expanding abaxially.

Description. –Cranidium almost as long as wide,

moderately convex (sag. and tr.). Maximum width

at ω, with 83% at δ. Glabella subquadrate, widens

slightly anteriorly, moderately convex (tr.); 80% as

long as wide, maximum width across occipital

ring, and 75% length and 67% width of cranid-

ium. Occipital ring is 25% as long as wide, forms

20% of glabellar length and is 5% longer than

anterior border; occipital tubercle posteriorly

placed. Lateral occipital lobe large, narrowly trian-

gular, 45% as long as wide, occupies 30% width

of occipital ring; intraoccipital furrow deep. S1

deep, trends at about 25°, meets axial furrow at

midglabellar length, occupies 40% of glabellar

width; S2 meets axial furrow at 35% length from

anterior glabellar margin, occupies 12% of glabel-

lar width; S3 is absent. Palpebral lobe long and

narrow, 35% as wide as long, occupies 30% crani-

dial length and 12% cranidial width, posterior

margin in line with occipital furrow. Preglabellar

ﬁeld gently convex, 11% cranidial length. Anterior

border 15% cranidial length, ﬂat and strongly

upturned.

Pygidium narrow and subtriangular. Axis

approximately 30% pygidial width anteriorly com-

prises eight rings and a terminal piece that is 12%

of axial length; ring furrows narrow. Pleural lobe

with ﬁve ribs that widen abaxially and are sepa-

rated by narrow, deep pleural furrows that reach

posterior border; pleural furrows incised abaxially

on ﬁrst two ribs which are ﬂat-topped in proﬁle.

Posterior border long, weakly convex, 15% of pygi-

dial length sagittally and about 50% this laterally.

Cephalon and pygidium smooth.

Discussion. –We have been unable to locate the

type specimens of Prantlia biloba, and this

description is based on the original illustrations

of Kobayashi & Hamada (1974, p. 114, text-ﬁg.

8F; pl. 12, ﬁgs 8, 9). Kobayashi (1985) reassigned

P.biloba to Latiproetus, due to difference from

Prantlia in the size and position of the palpebral

lobes. Sun (1990) considered these characters to

have no generic value, but highlighted the follow-

ing differences of Latiproetus from Prantlia:a

shorter preglabellar ﬁeld, the presence of an ante-

rior and lateral cephalic border furrow (and not

an epiborder furrow), a longer and wider glabella,

a less pronounced S1, a shorter occipital ring,

weaker pleural and interpleural pygidial furrows

and the lack of a broad pygidial border furrow

and border. Based on its possession of these

characters, we retain this species in Latiproetus.

Order Aulacopleurida Adrain, 2011

Family Aulacopleuridae Angelin, 1854

Subfamily Otarioninae Richter & Richter,

1926

Genus Maurotarion Alberti, 1969

Type species. –Harpidella maura Alberti, 1967,

from the Ludlow of Morocco.

Stratigraphical and geographical range. –Silurian of

the USA, Canada, Europe, Morocco and Australia;

Devonian of the USA, Europe, Morocco, Turkey,

Australia, Bolivia and Japan.

Maurotarion megalops (Kobayashi & Hamada,

1977)

Figure 7L, O, Q, S

1974 Otarion sp. Okazaki, pl. 9, ﬁgs 10, 11.

1977 Otarion megalops, Kobayashi and Hamada, sp.

nov. Kobayashi & Hamada, pl. 3, ﬁgs 2–4; text-

ﬁg3K

Holotype. –A cephalon (both internal and external

moulds, KT-20160520-03A), from Locality 3

(Table 1).

Paratypes. –Thoracopygon (KT-20160520-03B)

and cephalon (KT-20160520-03C), from Locality

Other material. –External mould of a juvenile

cranidium (OUMNH DY.15), from Locality 3, iden-

tiﬁed during this study.

Diagnosis. –Cephalon with broad, gently convex

anterior and lateral borders, and long robust

genal spine. Interocular ﬁxigenae very narrow.

Glabella moderately inﬂated, not overhanging the

preglabellar ﬁeld. L1 small, approximately 15% of

total glabellar width; S1 meets axial furrow at

62% length from anterior margin of glabella and

30% of its maximum width. S2 very short (tr.);

S3 absent. Thorax lacks axial spine on sixth

FOSSILS AND STRATA Silurian and Devonian proetid trilobites of Japan 229

segment. Pygidium very small with two axial

rings and two pleural ribs.

Description. –Cephalon 60% wider than long, mod-

erately convex (tr. and sag.). Cranidial width at ω

approximately 75% total width of cephalon. Glabella

subquadrate to subovate with well-rounded anterior

margin, moderately convex (tr.), 55% width of crani-

dium with maximum width across anterior of L1.

Occipital ring moderately convex, 15% glabellar

length; slightly longer medially than laterally; median

tubercle about twice as coarse as other tuberculation

on the occipital ring, posteriorly positioned. The cen-

tral area of the pre-occipital glabella is subpyriform

and strongly convex (sag. and tr.). S1 deep, diagonal,

meets axial furrow at approximately 62% from ante-

rior margin of glabella; L1 represents approximately

15% of total glabellar width, with moderate lateral

protrusion from outline of glabella. Preglabellar ﬁeld

moderately short; preglabellar furrow incised. S2 very

short (sag.), in line with anterior margin of eye.

Anterior border weakly convex, about as long as

preglabellar ﬁeld; anterior border furrow shallow and

broad. Interocular ﬁxigenae very narrow. Lateral and

anterior borders of equal breadth; posterior border

half as broad as anterior border. Eye platform large;

eye socle narrow (tr.). Librigenal spine long, curved.

Thorax has 11 segments. Axis roughly 70% wider

than pleural ﬁeld and moderately convex (tr.). Axial

rings essentially exfoliated except for ninth ring on

left side; axial furrow shallow. Pleurae widening

(exsag.) abaxially from about 50% width of segment.

Pleural furrows broad (exsag.), moderately shallow;

weak boss on anterior pleural band at adaxial edge of

articulating facet.

Pygidium very small, subovate in dorsal view, 25%

as long as wide. Axis with two axial rings, moderately

convex (tr.), approximately 50% as long as wide and

approximately 40% of maximum pygidial width.

Pleural lobe slightly wider than axis, with two poorly

preserved ribs; furrows not discernible on the inter-

nal mould. Posterior border not preserved.

Pre-occipital glabella with dense, moderately

coarse tubercles, coarsening medially; occipital ring

with two transverse rows of ﬁve coarse tubercles,

coarsening medially. Librigena and ﬁxigena with

sparse, coarse, rounded tubercles with interspersed

ﬁne tubercles.

Discussion. –We agree with Kobayashi & Hamada

(1977) that the cephalothorax and thoracopygon on

the same block which they described and which they

assigned to O. megalops belong to one individual. In

this specimen, the detached thoracopygon has ten

segments whilst the cephalothorax has one attached

thoracic segment. This species was assigned to Otar-

ion, without any supporting reasons. However,

based on the following characters, it is herein reas-

signed to Maurotarion: moderately convex (tr.) gla-

bella; prominent L1 with moderate protrusion from

lateral glabellar margin; broad anterior border; large

palpebral lobe and eye; and the absence of an axial

spine on the sixth thoracic segment (present only in

some species of Maurotarion –see Adrain & Chat-

terton 1994).

Maurotarion megalops has a more sculptured

cephalon and slightly more convex (sag.) glabella

than most species of Maurotarion (see Adrain &

Chatterton 1994; Adrain 2009). In the sculpture of

coarse granules, it is similar to M. struszi (Chatter-

ton, 1971) from the Emsian Waroo Limestone of the

Yass Basin of New South Wales, Australia, but

M. struszi has a much longer and more curved genal

spine and a thoracic axial spine.

Acknowledgements

We are grateful to The Leverhulme Trust (Interna-

tional Network) Grant IN-2014-025, ‘Assembling

the Early Palaeozoic terranes of Japan’, awarded to

Williams, for funding this research. We thank

Allaart Van Viersen (Natuurhistorisch Museum

Maastricht) for discussion on aulacopleurid system-

atics; Yujing Lin (Yunnan University) for translat-

ing Chinese literature; the curators of Tokyo

University Museum, Kyoto University Museum,

Yokokurayama National Forest Museum, Sakawa

Geology Museum, Iwate Prefectural Museum and

Ofunato City Museum, for help and access to spec-

imens; Mr Yoshiaki Mizuno of the Tokai Fossil

Society for the donation of his trilobite specimens

to the University Museum, Nagoya University. We

also thank James Mawson, Aqqid Saparin, Thomas

Gray, Harrison Bush and Michael Sekula for tech-

nical assistance at Leicester University. We are very

grateful to Bob Owens and Alan Thomas for their

very thorough reviews of an earlier version of this

manuscript.

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232 Stocker et al. FOSSILS AND STRATA

Proetid trilobites from the middle Telychian (Llandovery, Silurian) Ningqiang Formation, Shaanxi, China

Article

Full-text available

Dec 2020
Palaeoworld

Four proetid trilobite species, Chuanqianoproetus guizhouensis Yin in Yin and Li, 1978, C. shuangheensis Wu, 1977, C. sp., and Latiproetus guizhouensis Yin in Yin and Li, 1978, are described from the Ningqiang Formation in Ningqiang County, Shaanxi, China. They are middle Telychian (Llandovery, Silurian) in age. Chuanqianoproetus and Latiproetus are both regarded as members of the subfamily Warburgellinae; the former has been considered to be a junior subjective synonym of Astroproetus

Papers from the 6th International Conference on Trilobites and their Relatives

Chapter

Apr 2019

This volume arises from the 6th International Conference on Trilobites and their Relatives held in Tallinn, Estonia, in July 2017. Seven papers on trilobites are included in the volume and are briefly summarized here. They range from systematic descriptions of taxa to considerations of ontogeny, biofacies, biostratigraphy and taphonomy, and together, they encompass trilobites from the Early Cambrian to the Late Devonian. The volume also includes a report of the Tallinn conference and a review of those that went before it.

Trilobites of the suborder Illaenina from the Silurian of north Queensland, Australia

Article

Full-text available

Jul 2016

The trilobite fauna of the middle Silurian (Telychian to possibly earliest Sheinwoodian) Tomcat Creek limestone in the Broken River Province of north Queensland is dominated by the suborder Illaenina, including illaenimorphs (Illaeninae and Bumastinae) and members of the Scutelluidae. Scutelluidae are most diverse, with eight genera, of which Dolabrapex, Iotoryx, Perizostra, and Quintonia are new. Perizostra is the first scutelluid with a cephalon that may be described as of phacomorph appearance. Illaenimorphs are represented by three genera, including Opsypharus, which is regarded as a senior synonym of Paracybantyx but distinct from Failleana with which it has been placed in synonymy by some authors. Thirteen species are new: Cybantyx? ergodes, Opsypharus pandanensis, Australoscutellum talenti, Dolabrapex acomus, Illaenoscutellum psephos, Iotoryx clarksoni, Japono-scutellum mawsonae, J. drakton, J. fractum, Kosovopeltis avita, Perizostra campbelli, Quintonia arata, and Q. pavo. A species of Stenoparia is placed in open nomenclature. The species of Australoscutellum, Illaenoscutellum, and possibly Kosovopeltis are the oldest known representatives of those genera. These genera and Japonoscutellum are also common in faunas from limestones of Wenlock to Ludlow age in central western New South Wales, reflecting the similarity in lithofacies. The monotypic Late Ordovician genus Craigheadia, which has been regarded as a scutelluid, belongs to the Lichidae and is probably a junior synonym of Leiolichas.

Proetida — a new order of trilobites

Chapter

Jul 1975

Class Trilobita Walch, 1771. In: Zhang, Z.-Q. (Ed.) Animal biodiversity: An outline of higher-level classification and survey of taxonomic richness

Article

Dec 2011

Jonathan M. Adrain

Biogeographical and Biostratigraphical Significance of a New Middle Devonian Phacopid Trilobite from the Naidaijin Formation, Kurosegawa Terrane, Kyushu, Southwest Japan

Article

Jan 2018

A newly discovered trilobite from the Naidaijin Formation in the Kurosegawa Terrane of southwest Japan is referred to Toxophacops (Atopophacops) fujiwara sp. nov. The trilobite occurs in strata 2 m below a level with detrital zircons that yield an age of 383.9±4.4 Ma that is likely Givetian (late Mid-Devonian). Elsewhere, Early to Mid-Devonian trilobite species of T. (Atopophacops) and T. (Toxophacops) have been recorded from the Nakazato Formation of the South Kitakami Terrane of northeast Japan, and from the Zhusilenghaierhan region of western Inner Mongolia, North China. The new trilobite species extends the geographical range of the phacopid subfamily Echinophacopinae, and supports the affinities of some Devonian Japanese trilobites with those of north China. The occurrence of Toxophacops in the Lower Member of the Naidaijin Formation, combined with other trilobite evidence, confirms a clear biostratigraphical distinction between the Lower Member (upper Lower and Middle Devonian) and Upper Member (Upper Devonian) of the Naidaijin Formation.

Neue obersilurische sowie unter- und mitteldevonische Trilobiten aus Marokko, Deutschland und einigen anderen europäischen Gebieten. 2

Article

Jan 1967

G.K.B. Alberti

Silicified Lower Devonian trilobites from New South Wales

Article

Jan 1979
Palaeontology

Bohemian Silurian and Devonian Proetidae (Trilobita)

Article

Jan 1980

M. Šnajdr

The aulacopleurid trilobite Otarion, with new species from the Silurian of northwestern Canada

Article

Mar 1994

The genus Otarion Zenker, 1833, first appears in the Wenlock simultaneously with Cyphaspis Burmeister, 1843, as the oldest known species of each occur together in the southern Mackenzie Mountains of the Canadian Northwest Territories. The genera are unambiguous sister groups, a relationship supported most compellingly by a uniquely derived and distinctive pattern of juvenile cephalic spines, shared also with the Carboniferous genus Namuropyge Richter and Richter, 1939. This sister group relationship permits the development of a robust and stratigraphically correlated hypothesis of relationship among the adequately known species of Otarion, Otarion, Cyphaspis , and Namuropyge constitute the tribe Otarionini. The Mississippian genus Dixiphopyge Brezinski, 1988, may also belong to Otarionini. Namuropyge is a paedomorph, likely derived from a Degree Six or Seven meraspid of an older species of uncertain position in the Otarion–Cyphaspis clade. Three Wenlock species of Otarion occur in stratigraphic succession in a single section in the Mackenzie Mountains. Analysis of morphological change with time, and of sequential ontogenies, suggests that the Silurian history of the genus was dominated by incidents of peramorphosis. New species are Otarion huddyi, O. beukeboomi , and O. coppinsensis. Otarion brauni Perry and Chatterton, 1979, is revised.

Ontogeny, hypostome attachment and trilobite classification

Article

Jan 1990

Richard Alan Fortey

The high level classification of trilobites has proved particularly difficult. This paper discusses the classification of those trilobites which have been placed in the Order Ptychopariida, together with other relevant groups, including Agnostida. Although often considered "generalized', the ptychoparioids have a distinctive derived character: the hypostome is not exoskeletally connected to the cephalic doublure (natant hypostomal condition). The wide distribution within the Trilobita of the natant hypostomal condition is established. -from Author

The Encrinuridae and related trilobite families, with a description of Silurian species from southeastern Australia

Article

Jan 1980

Desmond Leslie Strusz

The Silurian and Devonian proetid and aulacopleurid trilobites of Japan and their palaeogeographical significance

Abstract

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