The earliest known strophomenoids (Brachiopoda) from early Middle Ordovician rocks Of South China

THE EARLIEST KNOWN STROPHOMENOIDS

(BRACHIOPODA) FROM EARLY MIDDLE

ORDOVICIAN ROCKS OF SOUTH CHINA

by ZHAN RENBIN1*, JIN JISUO2 , RONG JIAYU1 and LIANG YAN1

1State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 210008, China;

e-mail: [email protected] of Earth Sciences, University of Western Ontario, London, Ontario N6A 5B7, Canada; e-mail: [email protected]

*Corresponding author.

Typescript received 19 November 2012; accepted in revised form 3 March 2013

Abstract: The upper Daguanshan Formation (middle Ex-

pansograptus hirundo graptolite biozone, Dapingian, early

Middle Ordovician) of the Shuanghe area, Changning

County, southern Sichuan Province, contains three new gen-

era and species of strophomenoids: Ochyromena plana,

Shuangheella elongata, and Primotimena globula, which are

attributed to the Strophomenidae, Rafinesquinidae and Gly-

ptomenidae respectively. These are the earliest known strop-

homenoids from the South China palaeoplate, and also the

oldest rafinesquinid and glyptomenid brachiopods world-

wide. Global review of the superfamily Strophomenoidea of

Middle Ordovician age suggests that the first diversity peak

at the species level occurred in late Darriwilian (Llanvirn)

time, mainly as a result of the rapid diversification of the

family Strophomenidae. The first appearance datum (FAD)

of strophomenoids and their possible westward dispersal

were from North China (latest Floian) and/or South China

(early Dapingian), through the Chu-Ili terrane of Kazakh-

stan, Iran, and Baltica (early Darriwilian), to Avalonia and

Laurentia (late Darriwilian). This points to the existence of

early diversification hotspots of the strophomenoid super-

family in the North and South China palaeoplates during the

early Middle Ordovician in generally shallow water (corre-

sponding to BA2) environments. The high degree of similar-

ity in the external morphology and ventral interior of the

three new genera indicates that the early diversification of

strophomenoids began with differentiation of the cardinalia,

especially in the configuration of the bilobed cardinal pro-

cess, a key evolutionary novelty for the strophomenoids.

Key words: Strophomenoidea, Brachiopoda, Diverdifica-

tion, Middle Ordovician, South China.

STROPHOMENOIDS and plectambonitoids constitute two

major superfamilies of the order Strophomenida, and

their early fossil record is of great significance for under-

standing brachiopod evolution and radiation during the

Ordovician. For the past few decades, the origin of strop-

homenoids has remained a puzzling topic. Spjeldnæs

(1957, p. 194) suggested that strophomenoids probably

originated from ‘the geologically older Plectambonitacea’,

although he also admitted the possibility of strophome-

noids being a polyphyletic group. He divided strophome-

noids into a Kjaerina-Hedstroemina group and an

Oepikina group, but contended that many genera did not

fit in any of these two groups. In a comprehensive review

of the strophomenoid phylogeny at the generic, subfami-

lial, and familial levels, Pope (1976) proposed both two

dimensional and three dimensional models of strophome-

noid evolution, but the taxonomic basis of Pope’s phylo-

genetic hypothesis has since become outdated. Williams

and Hurst (1977, pp. 95–97) suggested that the order

Strophomenida is polyphyletic and that both the Strop-

homenoidea and Plectambonitoidea superfamilies evolved

from the Nisusiidae (Kutorginida, Kutorginata). During

their revision of the strophomenides for the Treatise,

Cocks and Rong (1989) proposed that the Strophomenoi-

dea may have evolved from a primitive leptellinid (e.g.

Apatomorpha or Toquimia) before Llanvirn (late Darriwil-

ian) time (see also Rong and Cocks 1994). In describing

the earliest known strophomenoid, Hesperinia sinensis,

Rong et al. (1999) noted more specifically that key inno-

vations in the origin of the Strophomenoidea are the

development of a bilobed cardinal process, a pair of

postero-laterally curved socket ridges, and transmuscle

ridges and side septa in the dorsal valve.

Obviously, in investigating the early evolutionary his-

tory of strophomenoids, the fossil records during the

Early and Middle Ordovician are crucial.

As part of the project on the ‘Great Ordovician Biodi-

versification Event (GOBE) in South China’ conducted in

© The Palaeontological Association doi: 10.1111/pala.12039 1121

[Palaeontology, Vol. 56, Part 5, 2013, pp. 1121–1148]

the past 10 years, several classic Lower–Middle Ordovician

sections were measured in great detail and large and sys-

tematic fossil collections were made from these sections on

the Upper Yangtze Platform (South China palaeoplate). In

general, brachiopods make up 80 per cent or more of the

collections and, more importantly, fossils of different eco-

types (such as planktonic graptolites, vagile trilobites, ben-

thic brachiopods, and even nektic nautiloids) occur

together in the same bed or separately in closely spaced in-

terbeds, providing reliable biostratigraphical control on the

correlation as well as good palaeoecological data for the

measured sections. Recently, several occurrences of Middle

Ordovician strophomenoids have been reported from

South China, such as Glyptomena sp. (see Zhan and Rong

2003), Pentagomena parvicostellata Zhan and Jin, 2005a,

Glyptomena? rugulosa Zhan and Jin, 2005a, and Heterome-

na dorsiconversa Zhan and Jin, 2005a. The previously

known strophomenoid record of South China can be

traced back to the Exigraptus clavus Biozone (late Dapin-

gian). This is at least two graptolitic biozones younger than

in North China, where the earliest known strophomenoid

Hesperinia sinensis occurs in the basal and lower Sandao-

kan Formation (Baltoniodus triangularis conodont Biozone

or Azygograptus suecicus graptolitic Biozone, top Floian to

basal Dapingian). Since 2000, systematic collections from

the upper Daguanshan Formation (Expansograptus hirundo

Biozone) at Shuanghe, southern Changning County,

southern Sichuan Province, southwestern China (Fig. 1),

have yielded strophomenoids that not only extend their

earliest occurrence in South China down to the lower Da-

pingian but also fill in a gap between the stratigraphic

ranges of strophomenoids of North China and South

China. Thus the primary object of this paper is to describe

these earliest known strophomenoids from the Daguan-

shan Formation of South China palaeoplate. A global sur-

vey of Middle Ordovician strophomenoid faunas is also

attempted to investigate their diversity change and palaeo-

biogeographical implications.

LOCALITY AND GEOLOGICAL SETTING

Palaeogeographically, Shuanghe of Changning was located

on the Upper Yangtze Platform (South China palaeoplate),

in proximity to a chain of emergent highlands (known as

‘oldlands’ in Chinese literature) along the western margin

of the palaeoplate (Fig. 1C). The Ordovician sequence in

the study area, particularly the Lower to Middle Ordovi-

cian series, is ‘essentially different from that of any other

places on the Yangtze Platform’ (Mu et al. 1978, p. 106).

As a result, a separate set of lithological units (e.g. the

Wanjuanshu, the Putaojing, the Daguanshan and the

Dashaba formations) has been in use in contrast to those

for the main part of the platform. The Daguanshan Forma-

tion (originally called the Shuanghe Formation, Zhu and

Rong 1994) is approximately correlative with the Meitan

Formation in the central part, and the Dawan Formation

500km

8 km

A

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YangtzeRiver Yangtze

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C H I N A

South China

Palaeoplate

B

25°

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105° 110°

115°

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110°

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Hannan Old Land

ChuanxiOld Land

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UpperYangtzePlatform

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LowerYangtzePlatform

F IG . 1 . Geographical and palaeogeographical maps of the study

area. A, Map of China, with the Yangtze Platform and Jiangnan Slope

of the South China palaeoplate delimited by two thick lines. Solid

star indicates approximate position of the study area enlarged in B.

B, Simplified location map of the section site, which is marked by a

striped square at Shuanghe. C, Palaeogeographical reconstruction of

the Yangtze Platform and Jiangnan Slope showing the approximate

position (little solid square) where the earliest known strophome-

noids of South China are found (base map from Zhang et al. 2002).

1122 PALAEONTOLOGY , VOLUME 56

in the northeastern part, of the Upper Yangtze Platform.

Lithostratigraphically, the Daguanshan Formation is dis-

tinct in its exclusively siliciclastic facies, consisting of mud-

stone, siltstone and sandstone, locally with trough cross

stratification that indicates a relatively high-energy deposi-

tional environment (Zhan et al. 2006). At the Shuanghe

section, the Daguanshan Formation is 373 m thick (Zhan

et al. 2005), notably thicker than its coeval stratigraphical

units in other parts of the Yangtze Platform. The formation

is only locally fossiliferous but careful collections yielded

more than 1500 brachiopod specimens, as well as some tri-

lobites, graptolites, and bivalves, in 58 samples (Zhan et al.

2004). Strophomenoids occur in the siltstone and mud-

stone of the upper Daguanshan Formation (Collection

AFI57 and upwards, see details in Zhan et al. 2004, 2005).

The brachiopod assemblage of this collection comprises

mainly lingulids and orthides, such as Lingulella, Ecteno-

glossa, Desmorthis, Metorthis, Nothorthis, and Pseudo-

mimella. This assemblage has been assigned to the ‘indet.

strophomenoid Association’ that occurs also in the upper

Meitan Formation at Honghuayuan, Tongzi, northern

Guizhou Province (Fig. 1C), in a relatively shallow-water

depositional setting (middle BA2; see Zhan et al. 2006 for

detailed discussion).

EARLY DIVERSIFICATIONS OFSTROPHOMENOIDS IN SOUTH CHINA

The earliest strophomenoids are known from the mar-

ginal area of the North China palaeoplate, represented by

Hesperinia sinensis Rong et al., 1999, from the argillaceous

limestone of the basal and lower Sandaokan Formation

(upper Floian to lower Dapingian) of western Inner Mon-

golia. Hesperinia was first reported from much younger

rocks (middle to upper Darriwilian) of the United States,

typified by H. kirki Cooper, 1956. The disappearance of

Hesperinia in North China seems to have been controlled

by lithofacies where the succeeding Ordovician strata

above the Sandaokan Formation are predominantly dolo-

mitic limestone over vast areas of the North China Plat-

form (Chen et al. 1984; Y. Zhang, pers. comm. 2011).

Instead, strophomenoids reappeared on the silty or

muddy substrates of the South China palaeoplate during

the earliest Middle Ordovician, associated with the first

pulse of the GOBE, recognized in South China at several

sections (Zhan et al. 2005, 2007). At that time, South

China was in close proximity to the North China palaeo-

plate and situated also in low tropical latitudes (Cocks

and Torsvik 2004; Boucot et al. 2009). Among their first

occurrences in South China, the strophomenoids were

represented by the oldest known members of the

Rafinesquinidae and the Glyptomenidae, and the second

oldest Strophomenidae (Fig. 2), which may also indicate

that the differentiation of strophomenoids from the plec-

tambonitoids may have occurred shortly after the origina-

tion of plectambonitoids in the early Floian (Cocks and

Rong 1989; Rong et al. 1999).

These early strophomenoids in South China, although

recognized as three different genera representing three

strophomenoid families in this study, share some common

features, such as a plano-convex to gently concavo-convex

profile, a subcircular outline, densely spaced and nearly

equal-sized costellae, and thin dental plates that serve also

as postero-lateral bounding ridges of the ventral muscle

field (Fig. 3). Their cardinalia, however, are drastically dif-

ferent, spanning the entire range of Type-A (Ochyromena,

Fig. 4A, D, G, J), Type-B (Shuangheella, Fig. 4B, E, H, K)

and Type-C (Primotimena, Fig. 4C, F, I, L) respectively, as

defined by Rong and Cocks (1994) as the fundamental

diagnostic characters for the classification of the superfam-

ily Strophomenoidea. This suggests that the early diversifi-

cation of strophomenoids began with a morphological

differentiation of the cardinalia, particularly the cardinal

process, a key autapomorphic character for the strophome-

noids. Since the origination of the strophomenoid-type

bilobate cardinal process, the two lobes of the cardinal pro-

cess evolved in three different directions: (1) strong and

stout lobes that extend prominently towards the posterior

on an apparent notothyrial platform, to become positioned

mainly posterior of the hinge line, with straight or postero-

laterally curved, thick ridge-like brachiophores (Type-A);

(2) elongate and plate-like lobes that project antero-ven-

trally on a variously developed (normally weak) notothyri-

al platform, positioned mainly anterior to the hinge line,

with normally straight, thin ridge-like brachiophores

(Type-B); and (3) delicate small lobes that are located lar-

gely posterior to the hinge line, with straight, low and thin

plate-like brachiophores fused to the baso-lateral sides of

the cardinal process (Type-C).

The palaeogeographical distribution of the oldest strop-

homenoids, represented by the archetypes of three fami-

lies, implies that an evolutionary cradle may have existed

in the North China and South China region or their

vicinity during the Early Ordovician. Interestingly, the

early representatives of strophomenoids in North and

South China thrived mainly in shallow water (corre-

sponding to BA2) depositional environments (Rong et al.

1999; Zhan et al. 2006), which corroborates the ‘onshore-

offshore hypothesis’ (Jablonski et al. 1983) for the palaeo-

ecological expansion of Phanerozoic Evolutionary Faunas.

Besides the shallow water background, the successful dis-

persal and early diversification into three strophomenoid

families in South China may have been related to a num-

ber of conducive palaeoecological factors, such as soft

substrates, warm water, and sufficient nutrient supply in

an area not far away from the oldlands in the Changning

area (Mu et al. 1978; Zhan 2003; Zhan et al. 2006). This

RENBIN ET AL . : OLDEST STROPHOMENOIDS OF SOUTH CHINA 1123

pulse of diversification of pioneer strophomenoids in

South China was followed by a much greater episode of

diversification during the later Middle Ordovician (see

Zhan and Jin 2005a, b, and also Fig. 5 herein) when the

second diversity acme took place in South China (Zhan

et al. 2007). Thus, the pioneer species of the three strop-

homenoid families in South China, as reported in this

study, coincided with the first brachiopod diversity acme,

and they served as precursory stocks for their major

diversification during the second brachiopod diversity

acme (Zhan et al. 2008).

MIDDLE ORDOVICIAN RECORDS OFSTROPHOMENOIDS

Middle Ordovician strophomenoids have been reported

from at least eight tectonic plates or terranes. The level of

taxonomic study varies greatly from region to region, and

the known fossil records indicate that strophomenoids

were most abundant and diverse in Laurentia, South

China, and Baltica during late Middle Ordovician time.

North China

Hesperinia sinensis Rong, Zhan and Xu, 1999 (p. 41, pl. 1,

figs 1–16; text-figs 4–6) is the oldest known strophome-

noid, from the basal Sandaokan Formation (upper Floian

to lower Dapingian, Baltoniodus triangularis and Baltonio-

dus navis conodont biozones; An and Zheng 1990),

Zhuozishan, Wuhai City, western Inner Mongolia, North

China. It is possible that the basal Sandaokan Formation

at Zhuozishan is of late Floian age according to the latest

regional stratigraphical correlation (Y. Zhang, pers.

comm. 2012). Palaeogeographically, Zhuozishan was

located in the northwestern part of the Ordos Basin,

North China palaeoplate, belonging to the marginal plat-

form facies belt (Chen et al. 1995; Rong et al. 1999).

South China

Strophomenoids first became diverse in South China dur-

ing the middle-late Darriwilian (Zhan et al. 2008),

although the oldest known records are now traced back to

the early-middle Dapingian. Altogether, there are 17 gen-

era and 18 species reported from the Darriwilian rocks of

South China: Bellimurina, Christiania, Colaptomena,

Glyptomena, Heteromena, Kjaerina, Leptaena, Longvillia,

Ochyromena, Pentagomena, Platymena, Primotimena,

rafinesquinid gen. indet., Shuangheella, Strophomena,

strophomenid gen. indet. 1, strophomenid gen. indet. 2.

The species including their locations and horizons are

listed below from older to younger ages.

Fl o

i an

Da

pin

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arr

iwilia

n

Mid

dle

Ord

ovic

ian

L.

Ord

.

Chrono-strati-graphy Strophomenidae

Stem group of strophomenide (unknown)

Rafinesquinidae Glyptomenidae

(many other formsupward)

(evolution toconvexo-concave)


(evolution toconcavo-convex)


(evolution to plano- or concavo-convex)

Och

yro

me

na

Sh

ua

ng

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( pla

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( pla

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Oxo

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na

(co

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ve

)

(co

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vo

co

nve

x)

(co

nca

vo

co

nve

x)

(co

nve

xo

co

nca

ve

)

Three major groups of strophomenoids

(H. sinensis)

(Ochyromena gen. nov.) (Shuangheella gen. nov.) (Primotimena gen. nov.)

He

sp

rin

iasi n

esi s

Se

mn

an

ostr

op

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(pla

no

co

nve

x)

e n

(ge

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-co

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x)

F IG . 2 . Proposed origin and early

diversification of strophomenoids. The

stem-group strophomenoids may have

originated in the North China-South

China region or their vicinity during the

Early Ordovician. The picture showing

the cardinalia and dorsal muscle field of

Hesperinia sinensis is from Rong et al.

(1999, pl. 1, fig. 11).


Ochyromena plana gen. et sp. nov.; this paper.

Shuangheella elongata gen. et sp. nov.; this paper.

Primotimena globula gen. et sp. nov.; this paper.

Rafinesquinid gen. et sp. indet. (Zhan et al. 2005a), up-

permost Meitan Formation (Exigraptus clavus Biozone,

upper Dapingian), Honghuayuan, Tongzi County, nor-

thern Guizhou.

Glyptomena sp. (Zhan et al. 2005a), uppermost Meitan

Formation (Exigraptus clavus Biozone), Honghuayuan,

Tongzi, northern Guizhou. Found also in younger

rocks at several localities on the Upper Yangtze

Platform (Zhan and Jin 2005a).

Pentagomena parvicostellata Zhan and Jin, 2005a (p. 42,

pl. 12, figs 1, 13–16; pl. 13, figs 1, 2, 4, 6–13; pl. 14,

figs 1–4; text-figs 15A, 16A–B), Dashaba Formation

(upper Undulograptus austrodentatus Biozone to Didy-

mograptus murchisoni Biozone, Darriwilian) at Shuan-

ghe, Changning, southern Sichuan.

Glyptomena? rugulosa Zhan and Jin, 2005a (p. 46, pl. 11,

figs 16, 17; pl. 12, figs 2–4, 7–9; text-fig. 16F); same

locality and horizon as Pentagomena parvicostellata.

Heteromena dorsiconversa Zhan and Jin, 2005a (p. 45, pl. 14,

figs 8, 9, 11–14; text-fig. 16C–D), a rafinesquinid from the

same locality and horizon as Pentagomena parvicostellata.

Longvillia? sp. Zhan and Jin (2005a, p. 36, pl. 12, figs 5,

6, 10–12), a strophomenid from the upper Dashaba

Formation (middle Darriwilian) at Shuanghe, Chang-

ning, southern Sichuan.

Strophomenid gen. et sp. indet. 1 Zhan and Jin (2005a,

p. 36, pl. 13, figs 3, 5); from the same locality and hor-

izon as Longvillia? sp.

Strophomenid gen. et sp. indet. 2 Zhan and Jin (2005a,

p. 36, pl. 14, figs 5–7, 10); from the same locality and

horizon as Longvillia? sp.

Bellimurina sp., from the Shihtzupu Formation (upper Dar-

riwilian) at many localities on the Upper Yangtze Plat-

form, together with many other strophomenoids (e.g.,

Christiania sp., Kjaerina sp., Leptaena sp., Colaptomena

sp., Platymena sp., and Strophomena sp.) based on our large

collection made during the past decade (Zhan and Rong

2003; Zhan et al. 2005; Zhan and Jin 2007). Systematic

study of these collections is in progress.

Chu-Ili Range, Kazakhstan

Christiania hastata Rukavishnikova, 1956 (p. 149, pl. 4,

figs 10–13). Uzunbulak Formation (lower Darriwilian),

A B C

D E

F

F IG . 3 . Sketches of key specimens of new strophomenoids. A, D, F, Ochyromena plana gen. et sp. nov., NIGP149539, 149512, ventral

internal mould (A) and its local enlargement (D) showing details of dental plates and muscle field, and dorsal external mould (F)

showing multicostellae and sparse concentric laminae. B, E, Primotimena globula gen. et sp. nov., NIGP149536, ventral internal mould

and its local enlargement (E) showing details of dental plates and muscle field. C, Shuangheella elongata gen. et sp. nov., NIGP149532,

ventral external mould showing dense multicostellae. Scale bars = 2 mm.


Kujandysai, Chu-Ili Range, southern Kazakhstan. Topo-

type material redescribed by Nikitina et al. (2006, p. 174,

fig 22.1–4).

Oxostrophomena dubia (Rukavishnikova, 1956, p. 143, pl.

4, figs 1, 2; pl. 9, figs 2–8). Initially described as a

species of Strophomena from the Uzunbulak Formation

(lower Darriwilian) at Kujandysai, Chu-Ili Range, sout-

hern Kazakhstan. Subsequently designated as the type

species of Oxostrophomena by Nikitina et al. (2006, p.

173, figs 20.6–9, 21).

Esilia tchetvericovae Nikitin and Popov, 1985, a strop-

homenid from the Andriushenskaya Formation (top

A B C

D E F

G H I

J

K

L

F IG . 4 . Sketches of key specimens of new strophomenoids. A, D, G, J, Ochyromena plana gen. et sp. nov., NIGP149514, dorsal inter-

nal mould (A), its latex cast (G), and their local enlargements (D, J) showing details of cardinalia, notothyrial platform, and muscle

field. B, E, H, K, Shuangheella elongata gen. et sp. nov., NIGP149528, dorsal internal mould (B), its latex cast (H), and their local

enlargements (E, K) showing details of cardinal process, brachiophores, and muscle field. C, F, I, L, Primotimena globula gen. et sp.

nov., NIGP149545, dorsal internal mould (C), its latex cast (I), and their local enlargements (F, L) showing details of cardinal process,

brachiophores and muscle field. Scale bars = 2 mm.


Darriwilian), Ishim River, northern Kuprianovka, cen-

tral Kazakhstan.

Eastern Alborz Mountains, northern Iran

Semnanostrophia lata Ghobadi Pour, Popov, Kebria-Ee

Zadeh and Baars, 2011c (p. 270, fig. 3), lower Lashkarak

Formation (lower to middle Darriwilian), Deh-Molla and

Simeh-Kuh, eastern Alborz Mountains, northern Iran.

This is the earliest occurrence of strophomenoids outside

China with certain age determination.

Baltica

Up to now, there are nine genera and 12 species of Dar-

riwilian strophomenoids documented from Baltica,

mainly from Estonia. The nine genera are: Actinomena,

Bekkerina, Christiania, Estonomena, Kiaeromena, Pande-

rites, Septomena, Tallinnites, and Trotlandella. The 12 spe-

cies and their locations and horizons are listed below in

ascending order according to their ages.

Christiania oblonga (Pander, 1830), systematic revision

by Spjeldnaes (1957, p. 122, pl. 5, figs 17–22; pl. 6,

fig. 14; text-figs 5, 26B, 27, 31), horizon 4aa of Eiker-

Sandsvaer, Gullerud, Norderhov, and Ringerike

districts, Norway. This horizon is correlative mostly to

the early Darriwilian (G. Baarli, pers. comm. 2008)

and, therefore, this is the earliest known strophome-

noid in Baltica.

Trotlandella loki Neuman in Neuman and Bruton, 1974

(p. 96, figs 6, 12 A–G, 13 A–L), a furcitellid from a silt-

stone block of middle Darriwilian age, Hølonda,

Trondheim, Norway. This is one of the most primitive

strophomenids in Baltica, characterized by cardinal

process lobes impressed on the notothyrial platform,

elevated sockets, and an unbranched median ridge.

Panderites imbrex (Pander, 1830), a furcitellid from the

Aseri Stage (middle Darriwilian) of Pavlovsk, St. Peter-

sburg, Russia, and from the Kandle Formation (Aseri

Stage, middle Darriwilian) of northern Estonia (R~o~om-

usoks 2004, p. 24, pl. 6, figs 1–6).

?Septomena senecta R~o~omusoks, 2004 (p. 48, pl. 17, figs

10, 11), a rafinesquinid from the lower V€ao Formation

(Lasnam€agi Stage, upper Darriwilian) of Vahik€ula,

V€a€ana riverbank, northern Estonia.

Estonomena kalevi R~o~omusoks, 2004 (p. 53, pl. 22, figs

1–7), a rafinesquinid from the V€ao Formation of

Kadaka quarry and V€a€ana riverbank, northern Estonia.

?Estonomena lindae R~o~omusoks, 2004 (p. 54, pl. 22, figs

8–11), a rafinesquinid from the V€ao and K~orgekallas

formations (upper Darriwilian) of Lasnam€agi, town of

Tallinn, Estonia.

Tallinnites imbrexoidea (Sokolskaya, 1954) (R~o~omusoks

1993, p. 50, pl. 2, figs 1–4; 2004, p. 25, pl. 6, figs 7–13),

a furcitellid from the K~orgekallas Formation and the

upper V€ao Formation (upper Darriwilian), Kohtla-J€arve

Gymnogr.linnarssoni

Didymogr.murchisoni

Didymogr.artus

Undulogr.intersitus

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dentatus

Exigr.clavus

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.

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?

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He

sp

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ki r

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nsis

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l og

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en

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an

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me

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ne

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Laurentia

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(1) (17,18) (3,3) (9,12) (8,16) (4,5) (6,6)

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n

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ph

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p.

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acty

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ia a

stu

r ica

F IG . 5 . Stratigraphical ranges of strophomenoid species in eight palaeoplates (see text for details of each species). Graptolitic bioz-

ones are based on Zhang and Chen (2003, 2006) and Zhang Yuandong (pers. comm. 2012). Conodont biozones are based on Zeng

et al. (1987) and Wang Zhihao and Zhang Yuandong (pers. comm. 2012). Numbers in brackets of each block are the number of gen-

era and species, respectively. Abbreviations: Sp., Spain; Avalo., Avalonia.


region, northern Estonia. Originally assigned to Oepik-

ina by Sokolskaya (1954).

Kiaeromena estonensis (Bekker, 1921), a rafinesquinid

from the Kukruse Formation (top Darriwilian) of

Kukruse, northeastern Estonia. Originally assigned to

Leptaena by Bekker (1921); transferred to Kiaeromena

by Spjeldnaes (1957, p. 183).

Actinomena orta €Opik, 1930, a strophomenid from the Kuk-

ruse Formation of Kukers, northwestern Jewe, Estonia.

Bekkerina dorsata (Bekker, 1921), a rafinesquinid from

the Kukruse Formation at Kuders, J€arve, Estonia. Origi-

nally assigned to Rafinesquina; designated as the type

species of Bekkerina by R~o~omusoks, 1993.

?Septomena aff. juvenilis (€Opik, 1930) (R~o~omusoks 2004,

p. 48, pl. 17, figs 12, 13), a rafinesquinid from the K~or-

gekallas Formation and the upper V€ao Formation (top

Darriwilian), northern Estonia.

Septomena crypta (€Opik, 1930), a rafinesquind from the

Viivikon na Formation (top Darriwilian) of Estonia;

revised by R~o~omusoks (1989, p. 112, pl. 2, figs 4, 5).

Laurentia (North America and Scotland)

Strophomenoids were diverse in Laurentia, including

eight genera and 14 species of strophomenoids in the per-

icratonic areas: Christiania, Dactylogonia, Glyptomena,

Hesperinia, Kirkina, Rhipidomena, Strophomena, and Ter-

atelasma, all of which are of late Darriwilian age. The

confirmed 16 species, together with Toquimia kirki, are

listed below in ascending stratigraphical order.

Hesperinia kirki Cooper, 1956 (p. 822, pl. 213E, fig. 25;

pl. 229C, figs 9–15), Tank Hill Formation, and the

upper Pogonip Formation, Nevada. Hesperinia kirki is a

rare species in Laurentia.

Toquimia kirki Ulrich and Cooper, 1936 (see also Ulrich

and Cooper 1938, p. 184, pl. 38C, figs 9–16; and Coo-

per 1956, p. 698, pl. 164B, figs 4–14; pl. 195E, fig. 32);

upper Pogonip Formation, Nevada. Originally assigned

to the Plecambonitoidea. Ross (1970, p. 63, pl. 8, figs

16–18) suggested that ‘Toquimia is more closely related

to Strophomenidae than to Leptellinidae’ because he

found a bilobed cardinal process in T. kirki, which was

not adopted by Cocks and Rong (2000, p. 326) who

retained Toquimia as a leptellinid (the illustrated speci-

mens in the revised brachiopod Treatise are apparently

of plectambonitoid affinity). In this study, Toquimia

kirki is not included in the discussion because of its

taxonomic uncertainty.

Dactylogonia alternata Cooper, 1956 (p. 825, pl. 218D,

figs 11–14; pl. 218C, figs 22–30), a strophomenid from

the Lenoir Formation, Tennessee, and the Tumbez For-

mation, Virginia. The conodont data of Bergstr€om

et al. (1988) suggest that Cooper’s Marmorian stage

correlates approximately to the upper Llanvirn and

Llandeilo (upper Darriwilian).

Dactylogonia extensa Cooper, 1956 (p. 827, pl. 219B, figs 2–5),

from the Mingan Formation of Bald Island, Quebec.

Dactylogonia geniculata Ulrich and Cooper (1942, p. 624,

pl. 90, figs 19–23); Strasburg Limestone or the upper

Lenoir Formation, Tennessee; Arline Formation,

Virginia; Little Oak Formation, Alabama (Cooper 1956,

p. 827, pl. 216D, figs 14–30; pl. 217M, figs 38, 39; pl.

218B, figs 4–7; pl. 219E, fig. 11; pl. 219F, figs 12, 13).

Dactylogonia incrassata (Hall, 1847); originally described

as a Leptaena from the Middle Ordovician of New

York; transferred to Dactylogonia by Cooper (1956,

p. 828, pl. 219I, figs 16–23; pl. 219J, figs 24–27; pl. 220B,

figs 6–8; pl. 226C, figs 5–9) based on material from the

Crown Point Formation in New York and Vermont.

Dactylogonia vespertina Ross, 1970 (p. 67, pl. 9, figs 17–2-

2); upper Antelope Valley Limestone, Nevada.

Glyptomena distans (Raymond, 1906), originally named as

a species of Rafinesquina, and reassigned to Glyptomena

by Cooper (1956, p. 883, pl. 231B, fig. 8), Crown Point

Formation and Valcour Formation, New York.

Glyptomena minganensis (Twenhofel and Stiles in Twenho-

fel, 1938, p. 50, pl. 8, figs 3–6), originally described as a

subspecies of Rafinesquina champlainensis; questionably

reassigned to Glyptomena by Cooper (1956, p. 883)

based on material from the Mingan Formation of

Mingan Islands, St. Lawrence River, Quebec, Canada.

Glyptomena prisca (Raymond, 1905), originally described

as a species of Strophomena; transferred to Glyptomena

by Cooper (1956, p. 884, pl. 235A, fig. 1; pl. 235D,

figs 3, 4) based on new material from the Crown Point

Formation of New York and Vermont.

Kirkina millardensis Salmon, 1942 (p. 599, pl. 87, figs 34,

35); Pogonip Limestone, Utah (Cooper 1956, p. 866).

It was suggested to be an intermediate between

Oepikina and Rafinesquina (Salmon 1942).

Christiania subquadrata (Hall, 1883); generic assignment

to Christiania by Hall and Clarke (1892, p. 298, pl. 15,

figs 32, 33; pl. 15A, fig. 36). Top Darriwilian to lower

Katian (Mamorian to Chatfieldian), eastern and

western pericratonic regions of North America. For a

summary see Jin and Norford (1996).

Rhipidomena tennesseensis (Willard, 1928, p. 285, pl. 2, figs

17, 18), originally described as a species of Strophomena;

designated as the type species of Rhipidomena by Cooper

(1956, p. 870, pl. 252A, figs 1–5; pl. 252B, figs 6–14; pl.

253A, figs 1–14). Benbolt Formation (Porterfieldian,

approximately coeval with top Darriwilian; see Bergstr€om

et al. 1988), Virginia and Tennessee.

Strophomena filitexta (Hall, 1847); Sandbian to lower Kat-

ian (Turinian to Chatfieldian) strata, eastern North

America (e.g. Hall and Clarke 1892, p. 251, pl. 9A,

fig. 11; Wilson 1946, p. 102, pl. 9, fig. 13).


Teratelasma neumani Cooper (1956, p. 824, pl. 225B,

figs 5–23), from the Sevier Formation at Old Kagley

Church, Binfield Quadrangle, Tennessee.

Christiania sulcata Williams, 1962 (p. 194, pl. 18, figs

34–39); Stinchar Limestone, Girvan, Strathclyde.

Colaptomena macullumi (Reed, 1917, p. 865, pl. 11, figs

17–20); first described as Rafinesquina expansa from

the top of the Confinis Flags, Girvan; reassigned

questionably to Rafinesquina by Spjeldnaes (1959),

and further to Macrocoelia by Williams (1962), a junior

synonym of Colaptomena (Cocks and Rong 2000).

Avalonia

Only four genera and seven species of strophomenoids

were reported from the late Darriwilian rocks of Avalonia

mainly in Wales and Girvan districts. The genera include

Christiania, Colaptomena, Murinella and Rafinesquina,

and the species are listed as follows.

Christiania elusa Lockley and Williams, 1981 (p. 66, figs

231–240); sandy ashes beds, top of the Main Volcanic

Series (Didymograptus murchisoni Biozone), southwest-

ern Wales. This is one of the three earliest known stro-

phomenoid species of Avalonia.

Colaptomena llandeiloensis elongata (Lockley and Williams

1981, p. 65, figs 227–230), a rafinesquinid from the same

locality and horizon as Christiania elusa. This subspecies was

originally assigned to Macrocoelia, synonymized as a junior

synonym of Colaptomena by Cocks and Rong (2000).

Colaptomena llandeiloensis (Lockley and Williams 1981,

p. 62, figs 216–226); argillaceous shell beds, Flags and

Grits Formation and its equivalents (Didymograptus

murchisoni Biozone and Gymnograptus linnarssoni Bio-

zone), southwestern Wales. Originally described by

Davidson (1871, p. 316, pl. 46, figs 11–14) as a

Strophomena; questionably reassigned to Rafinesquina

by Spjeldnaes (1959); transferred to Macrocoelia by

MacGregor (1961), a junior synonym of Colaptomena

(Cocks and Rong 2000).

Murinella sp. Lockley and Williams (1981, p. 61, figs 213–

215), a furcitellid from the Flags and Grits Formation

in the middle of the Ffairfach Group, southwest-

ern Wales; also known from the Meadowtown Beds,

Shelve District, Shropshire (Williams 1974, p. 141, pl.

25, figs 2, 3).

Rafinesquina delicata Williams, 1974 (p. 141, pl. 25, figs

6–13); Meadowtown Beds, Shelve District, Shropshire.

Spain

Dactylogonia sp. nov., Reyes et al. (2011), from the

Darriwilian dark shales of the Central-Iberian Zone,

Central Spain (the Didymograptus artus Biozone, mid-

dle Darriwilian).

Dactylogonia asturica (Villas in Villas et al., 1989), Reyes

et al. 2011, p. 466, pl. 1, fig. B, from the El Castro For-

mation of the Asturian coast of northern Spain. This

species was originally described by Villas (in Villas et al.

1989) as Hesperinia asturica (p. 561, figs 2, 5.6–5.13,

6.1–6.13) and thought to be Ashgillian (late Katian) in

age. But Truyols et al. (1996) dated the rocks yielding

this species as Dobrotivian (late Darriwilian), coincid-

ing with the biostratigraphic correlation scheme of

Reyes et al. (2011).

Australia

There are six strophomenoid genera and species reported

from the uppermost Darriwilian of Tasmania, Australia.

Bellimurina aff. compressa Cooper, 1956 (Laurie 1991, p.

78, fig. 43B), from the upper Cashions Creek Lime-

stone, Settlement Road, Tasmania. Although similar to

North American material from the Bromide Formation

(Sandbian) Oklahoma (Cooper 1956, p. 855, pl. 221D,

figs 23–28) in several aspects, the Australian shells are

nearly twice as large as those from North America

(Laurie 1991).

Dactylogonia rara Laurie, 1991 (p. 71, figs 40D, 41A);

same locality and horizon as above.

Maakina sp. Laurie, 1991 (p. 74, fig. 42B); same locality

and horizon as above. Maakina is a furcitellid from the

Baksansk Horizon (Caradoc, Upper Ordovician) of Sib-

erian Platform (Andreeva in Nikiforova and Andreeva

1961), and the Australian record is its only occurrence

outside Siberia.

Oepikinid gen. et sp. indet. Laurie (1991, p. 76, fig. 45B);

same locality and horizon as above.

?Strophomena sp. Laurie, 1991 (p. 80, fig. 44C); same loc-

ality and horizon as above.

Teratelasmella plicata Laurie, 1991 (p. 84, figs 44D, 45A);

same locality and horizon as above. An endemic taxon to

Australia, characterized by an exceptionally high dorsal

median septum, a short well-developed ventral median

septum and a strongly plicate anterior commissure.

CHARACTERISTICS OF MIDDLEORDOVICIAN STROPHOMENOIDS ANDTHEIR PALAEOBIOGEOGRAPHICALIMPLICATIONS

From the strophomenoid data discussed above (see

also Fig. 5), several broad patterns and trends can be

recognized regarding the generic diversity change and


palaeobiogeographical affinities among the strophome-

noid faunas in several tectonic plates or terranes (Fig. 6).

The oldest known strophomenoids appeared along the

margin of the North China Platform, in a shallow-water,

inner shelf setting (BA2), with calcareous to argillaceous

mud substrate during the latest Early Ordovician to the

earliest Middle Ordovician (Rong et al. 1999; Y. Zhang,

pers. comm. 2012). They are represented by Hesperinia

sinensis, a strophomenid with a Type-A cardinalia (Rong

and Cocks 1994). Strophomenoids disappeared from

North China for most of the Middle Ordovician,

although this may have been due, at least partially, to

facies control and preservation/collection bias in the pre-

dominantly massive dolostone facies.

In South China, strophomenoids first appeared during

the early–middle Dapingian (Expansograptus hirundo

Biozone, a biozone younger than in North China and not

two biozones as it was previously considered, see Zhan

et al. 2005), also in a near shore, shallow-water environ-

ment (BA2), represented by three morphotypes attribut-

able to three different strophomenoid families,

respectively. In contrast to their occurrence in North

China, however, the strophomenoids radiated rapidly

shortly after their first appearance in South China and

became widespread over the vast area of the Yangtze

Platform rather than being confined to marginal settings.

The first major diversification of the early strophome-

noids occurred in middle Darriwilian time (Didymograp-

tus artus Biozone), marked by the rapid increase in

strophomenids and rafinesquinids, as part of the second

pulse of brachiopod radiation in South China (see Zhan

et al. 2007). This radiation lasted through two biozones

(D. artus and D. murchisoni biozones) in South China,

when strophomenoids were poorly known elsewhere in

the world.

South China has the most diverse strophomenoids

through Dapingian to Darriwilian, but only five out of the

17 genera were reported from slightly younger rocks of

other palaeoplates within Darriwilian. These include Chris-

tiania, Glyptomena, Bellimurina, Colaptomena and Strop-

homena, which may have served as the precursory stock of

the strophomenoids elsewhere in the world (Fig. 7). Their

initially restricted palaeogeographical range suggests that

faunal exchange among different blocks was very limited

during the early stage of strophomenoid evolution, and

each palaeoplate developed its own characteristic faunas,

particularly in South China, Laurentia and Baltica.

Iran has only one record of Darriwilian strophome-

noids, Semnanostrophia lata. This is also the earliest reli-

able strophomenoid outside North and South China

Gymnogr.linnarssoni

Didymogr.murchisoni

Didymogr.artus

Undulogr.intersitus

Undulogr.austro-

dentatus

Exigr.clavus

Expansogr.hirundo

Azygogr.suecicus

Corymbogr.deflexus

Are

nig

ian

Lla

nvir

ian

Ibe

xia

nW

hit

ero

ckia

n

Fl o

ian

Da

pin

gia

nD

arr

iwilia

n

Mid

dle

Ord

ovic

ian

L.

Ord

.

Pygodusserra

Eoplaco-gnathussuecicus

Lenodusvariabilis

Micro-zarkodina

parva

Paroistodusoriginalis

Baltoniodusnavis

Baltoniodustriangularis

Oepikodusevae

Chrono-strati-graphy N

ort

hA

me

rica

Bri

tish

Graptolitebiozones

Conodontbiozones

No

rth

Ch

ina

SouthChina

Chu-Ili

Kazakh-stan

Baltica Avalonia

Au

str

alia

Laurentia

1(S1)

1(S1)

3(S1,R1,G1)

5(S1,R2,G2)

5(S1,R2,G2)

3(R2,G1)

12(S4,R5,G2,C1)

11(S3,R5,G2,C1)

7(S2,R3,G1,C1)

2(S1,C1)

2(S1,C1)

1(S1)

2(S1,C1)

?

9(S5,R3,C1)

5(S2,R2,C1)

3(S2,C1)

1(C1)

4(S1,R2,C1)

2(R1,C1)

8(S4,R1,G2,C1)

5(S3,G1,C1)

1(S1)

6(S6)

Total

1(S1)

4(S2,R1,G1)

5(S1,R2,G2)

8(S3,R2,G2,C1)

6(S2,R2,G1,C1)

18(S10,R5,G2,C1)

18(S8,R7,G2,C1)

29(S17,R8,G3,C1)

Ira

n

1(S1)

1(S1)

1(S1)

?

?

Sp.

1(S1)

1(S1)

?

F IG . 6 . Generic diversity change of Middle Ordovician strophomenoids in eight palaeoplates, showing stepwise first appearance

datum (FAD) in increasingly younger strata from North China to Australia. Number in each graptolite biozone is the number of gen-

era of each palaeoplate, and the numbers in brackets are the number of genera of each particular given family: S, Strophomenidae; R,

Rafinesquinidae; G, Glyptomenidae; C, Christianiidae. Graptolite and conodont biozones are based on Zhang and Chen (2003, 2006),

Zeng et al. (1987), and Zhang Yuandong and Wang Zhihao (pers. comm. 2012). Abbreviation: Sp., Spain.


palaeoplates, which implies a certain degree of palaeogeo-

graphical affinity between North China, South China and

Iran. Such a palaeobiogeographical relationship was also

suggested in recent studies (e.g. Ghobadi Pour 2008;

Popov et al. 2008, 2009; Ghobadi Pour et al. 2011a, b, c).

Globally, strophomenoid radiation during Darriwilian

time occurred in two steps: the first in South China dur-

ing the middle Darriwilian, and the second in Laurentia,

Baltica, and Avalonia during the latest Darriwilian (Gym-

nograptus linnarssoni Biozone; see Figs 5–7). The diversity

increase manifested at both the generic and specific levels,

mostly within the family Strophomenidae as well as in

some groups of the Rafinesquinidae. Such radiation coin-

cided with the first major diversification of plectamboni-

toids (Cocks and Rong 1989; Harper et al. 2004; Zhan

et al. 2008), but slightly postdates the first global diversity

acme of the GOBE (Webby 2000) which occurred just at

the beginning of the Darriwilian (Undulograptus austro-

dentatus Biozone, Harper et al. 2004).

There is an apparent trend of progressively younger

first appearance datum (FAD) for the Strophomenoidea

across eight tectonic plates or terranes (Fig. 6), although

it is uncertain whether or not the pattern represents

actual dispersal pathways of the early strophomenoid fau-

nas (Fig. 7). The earliest known strophomenoids in

southern Kazakhstan and northern Iran occur at a similar

age, although the Kazakhstanian occurrences need to be

further assessed. The centre of origin may have been an

unknown island in the vicinity of the South China and

North China palaeoplates, followed by two dispersal

routes (Fig. 7). On the one hand, it migrated to higher

latitudes represented by only strophomenids such as the

occurrences in Iran and Spain (Villas et al. 1989; Ghobadi

Pour et al. 2011c; Reyes et al. 2011). On the other hand,

its migration to South China (lower latitude) was proven

to be very successful followed by several strong diversifi-

cations in South China, Baltica, Laurentia, etc. (see the list

of species in above section).

Among the Dapingian–Darriwilian strophomenoids

worldwide, only seven genera occur in two or more

blocks among 38 genera analysed in this study. Five of

seven genera (Bellimurina, Colaptomena, Dactylogonia,

Glyptomena and Hesperinia) are known in just two palae-

oplates or terranes, and one in three (Strophomena) and

one in five (Christiania) blocks, respectively. None of the

studied paired blocks have a similarity coefficient >0.4

(using several similarity measures such as Dice, Simpson,

Jaccard, and Raup-Crick). Such a low degree of faunal

similarity is in agreement with the hypothesis of Williams

(1973) that the late Middle Ordovician was a time of

strong faunal provincialism. This also supports the notion

that each diversity acme of the GOBE coincided with

strong global provincialism (Zhan and Jin 2008; Zhan

and Liu 2010).

SC

NC

KZ

BA

LA

AS

?

Strophomenoids from Dapingian to Darriwilian

30 30

6060

30

30

60

AV

TM

latest Floian

Dapingian

early Darriwilian

middle-late Darriwilian

N

IR

SP

F IG . 7 . Global distribution and possible expansion of the strophomenoids from late Floian to Darriwilian. Triangle: latest Floian to

earliest Dapingian, Azygograptus suecicus Biozone. Solid triangle: Dapingian, Expansograptus hirundo Biozone to Exigraptus clavus Bioz-

one. Circle: early Darriwilian, Undulograptus austrodentatus Biozone to Undulograptus intersitus Biozone. Solid circle: late Darriwilian,

Didymograptus artus Biozone to Gymnograptus linnarssoni Biozone. NC, North China; SC, South China; KZ, Kazakhstan; BA, Baltica;

AV, Avalonia; LA, Laurentia; TM, Tasmania; AS, Australia; IR, central and northern Iran; SP, central and northern Spain.


SYSTEMATIC PALAEONTOLOGY

Repository. Nanjing Institute of Geology and Palaeontology

(NIGP), Chinese Academy of Sciences.

Order LINGULIDA Waagen, 1885

Superfamily LINGULOIDEA Menke, 1828

Family PSEUDOLINGULIDAE Holmer, 1991

Genus PSEUDOLINGULA Mickwitz, 1909

Pseudolingula sp.

Figure 8A

Remarks. Two broken pieces of ventral internal moulds

are in the studied collection. From their general valve

shape, particularly the rounded posterior end and the

weak, narrow pedicle groove in the central posterior part,

they are provisionally identified as Pseudolingula. It is

about 6 mm wide with some clear concentric growth lines.

Order STROPHOMENIDA €Opik, 1934

Superfamily STROPHOMENOIDEA King, 1846

Family STROPHOMENIDAE King, 1846

Subfamily STROPHOMENINAE King, 1846

Genus OCHYROMENA gen. nov

Derivation of name. Greek, ochyros, strong, stout, referring to

the robust bilobed cardinal process of the type species.

Type species. Ochyromena plana gen. et sp. nov., upper Daguan-

shan Formation (lower to middle Dapingian), Shuanghe,

Sichuan Province, South China.

Diagnosis. Shell gently concavoconvex, multicostellate.

Dental plates thin, divergent. Ventral muscle field subcir-

cular to rhomboidal. Notothyrial platform present. Cardi-

nal process stout, bilobed. Socket ridges thick, short, with

antero-laterally extended ends in some specimens. Dorsal

muscle field lacking transverse and longitudinal ridges.

Species included. The type species only.

Remarks. The new genus is assigned to the Strophomeni-

dae because of its Type A cardinalia (Rong and Cocks

1994), characterized by a well developed notothyrial plat-

form, a postero-ventrally projecting, bilobed cardinal pro-

cess. The socket ridges are generally thick and short,

diverging at about 100 degrees, but in some specimens

they are laterally extended, subparallel to the hinge line

(e.g. Figs 8O, P, 9I–L). The absence of a median septum

and transmuscle ridges from the dorsal valve distinguishes

the new genus from most of the other genera of the fam-

ily. In the Strophomenidae, the new genus belongs to a

group with nearly planoconvex to concavoconvex shells,

such as Drummuckina, Biparetis, Dactylogonia, Geniculina,

Kirkina, Mansina, Molongcola, Oepikina, Panderites, Tal-

linnites, and Titanomena. Kirkina Salmon, 1942 from

the Pogonip Limestone (Chazyan, upper Darriwilian) of

Utah is particularly similar to Ochyromena gen. nov. in

its shell outline and profile, but differs in having less

numerous costellae, a weaker notothyrial platform,

much weaker cardinal process, and the presence of

transmuscle ridges. Molongcola Percival, 1991 from the

Trilobite Hill Limestone Member (Caradoc, Upper

Ordovician) of the Cliefden Caves Limestone of New

South Wales has a planoconvex shell approaching those

of the new genus, but it has much stronger dental

plates and a well developed dorsal median septum and

transmuscle ridges.

Semnanostrophia Ghobadi Pour, Popov, Kebria-Ee

Zadeh and Baars, 2011c is similar to Ochyromena gen.

nov. in their dorsal interiors. They both have planoconvex

lateral profile, but the Iranian genus has a much wider

shell outline, more clearly differentiated costellae (multi-

plying several times to produce costellae of different

sizes), and more strongly striated ventral muscle field (i.e.

with clear longitudinal muscle ridges). When established,

Semnanostrophia was assigned to the family Glyptomeni-

F IG . 8 . A, Pseudolingula sp., NIGP156553, posterior half of a ventral internal mould. B, Nothorthis perplexa Xu and Liu, 1984,

NIGP149508, dorsal internal mould. C–X, Ochyromena plana gen. et sp. nov. C, D, NIGP149509, paratype, ventral internal mould (C)

and its local enlargement (D) showing details of dental plates and muscle field. E–H, NIGP149510, paratype, ventral internal mould

(E), its latex cast (G), and their local enlargements (F, H) showing details of pseudodeltidium, teeth, dental plates, and muscle field.

I–K, NIGP149511, paratype, dorsal external mould (I), its latex cast (J), and local enlargement (K) showing evenly sized and spaced

multicostellae. L, NIGP149516, paratype, dorsal internal mould. M, N, NIGP149512, paratype, dorsal external mould (M) and its local

enlargement (N) showing evenly sized and spaced multicostellae. O, P, NIGP149513, paratype, dorsal internal mould (O) and its local

enlargement (P) showing details of cardinal process, socket ridges, and muscle field. Q–T, NIGP149514, holotype, dorsal internal

mould (Q), its latex cast (S), and their local enlargement (R, T) showing details of cardinal process, socket ridges, notothyrial plat-

form, myophragm and muscle field. U–X, NIGP149515, paratype, dorsal internal mould (U), its latex cast (W) and their local enlarge-

ment (V, X) showing details of cardinalia and muscle field. Scale bars = 1 mm unless otherwise noted.


A B C D

E

I

F G H

J K L

M

Q

U V W X

R S T

N O P


dae ‘because it has a bilobed cardinal process fused with

socket ridges and situated posterior to the hinge line’

(Ghobadi Pour et al. 2011c). It has a well developed not-

othyrial platform continuous antero-medially with the

low and wide median ridge, and two stout cardinal pro-

cess lobes projecting strongly towards the posterior, form-

ing a typical Type-A cardinalia (sensu Rong and Cocks

1994; Cocks and Rong 2000). In this regard, Semnanostro-

phia and Ochyromena gen. nov. should be assigned to the

family Strophomenidae.

Ochyromena plana sp. nov.

Figures 3A, D, F, 4A, D, G, J, 8C–X, 9A–N, 10, 11I–R, 12C, I–N

Derivation of name. Latin, planus, even, flat; with reference to

the nearly flat dorsal valve and very gently convex ventral valve

of this species.

Type specimens. Holotype, NIGP149514; paratypes, NIGP149-

507–149513, 149515–149522, 149539, 156513–156516, 156523,

156529–156532, 156533, 156534, from the upper Daguanshan

Formation (lower to middle Dapingian), Shuanghe, Changning

County, southern Sichuan Province.

Material. Six ventral internal and four external, 15 dorsal inter-

nal and seven external moulds, upper Daguanshan Formation

(lower to middle Dapingian), Shuanghe, Changning.

Diagnosis. Shell medium-sized, plano- to gently concavo-

convex, multicostellate, with well-developed pseudodeltidi-

um and incipient chilidium. Dental plates thin, widely

divergent. Ventral muscle field subcircular to rhomboidal,

without antero-lateral bounding ridges. Notothyrial platform

present but variously developed. Cardinal process bilobed,

robust, projecting towards posterior. Socket ridges thick,

extending mainly antero-laterally. Dorsal muscle field clearly

impressed, without any transverse and longitudinal ridges.

Description. Shell medium to large, subcircular to longitudinally

semielliptical in outline, with average length/width ratio of 0.78

(see Appendix S1); planoconvex to gently concavoconvex, with

ventral valve deepest in posteromedian portion. Maximum width

at hinge line or at about one-third of shell length; cardinal

extremities ranging from acute, rectangular, to rounded. Dorsal

geniculation weak, poorly developed in concavo-convex shells.

Anterior commissure rectimarginate. Ventral interarea planar,

apsacline, about 12 per cent length of shell; delthyrium covered

posteriorly by pseudodeltidium, with submesothyrid foramen.

Dorsal interarea planar, slightly hypercline, notably lower than

ventral interarea, normally <1 mm high; notothyrium covered

by thin, strongly arched chilidium. Multicostellae of similar size

(6–8 per 1 mm) and rounded crest, increasing in number anteri-

orly mainly by intercalation; similar width between costellae and

interspaces. Concentric fila not observed, except for several con-

centric lamellae developed anteriorly (Fig. 3F).

Delthyrial cavity large, deep. Teeth delicate, wedge-shaped,

with rounded crest. Dental plates thin, short, diverging from

each other at about 90 degrees, extending antero-laterally to

form weak lateral bounding ridges of muscle field. Lateral cavi-

ties narrow and very deep (Fig. 8F). Muscle field rhomboidal to

subcircular in outline, about one-third length and width of shell;

pair of oval adductor scars in posteromedian part of muscle

field, separated by weak median ridge; diductor scars subtriangu-

lar to transversely semicircular in outline, with their anterior

ends diverging at about 40 degrees (Figs 3A, D, 8C, D). Mantle

canal system saccate, poorly impressed; vascula media originat-

ing from anterior ends of diductor scars, diverging anteriorly at

narrow angle.

Cardinalia robust, about 12 per cent length and 28 per cent

width of dorsal valve; notothyrial platform well developed, mod-

erately elevated; cardinal process stout, bilobed, projecting poste-

ro-ventrally beyond hinge line; each lobe wedge-shaped, with

short, thick shaft, swollen myophore, and deep and narrow

groove between two lobes (Fig. 4A, D, G, J). Sockets shallow,

open antero-laterally; socket ridges low, thick, diverging from

each other antero-laterally at about 95–100 degrees, and fused

medially to base of cardinal process. Myophragm low, thick,

merging posteriorly with notothyrial platform. Muscle field sub-

circular to inverted trapezoidal in outline, about one-third

length and width of valve, without transmuscle ridges or bound-

ing ridges; posterior pair of adductor scars subcircular, widely

separated by thick myophragm; anterior pair slightly smaller and

elongate. Mantle canal system saccate, weakly impressed; area of

vascula genitalia with some very weak longitudinal ridges.

Both valves marked by peripheral crenulations for about

10 per cent of shell length or less (e.g. Figs 4G, 8S).

Variations. Several morphological variations are present within

a relatively small sample available for study:

F IG . 9 . A–N, Ochyromena plana gen. et sp. nov. A–D, NIGP149517, paratype, dorsal internal mould (A), its latex cast (C) and their

local enlargement (B, D) showing details of cardinalia and muscle field. E–H, NIGP149518, paratype, dorsal internal mould (E), its

latex cast (G) and their local enlargement (F, H) showing details of cardinalia and muscle field. I, J, NIGP149519, paratype, dorsal

internal mould (I) and its local enlargement (J) showing cardinal process and socket ridges. K, L, NIGP149520, paratype, dorsal inter-

nal mould (K) and its local enlargement (L) showing details of cardinal process and socket ridges. M, NIGP149521, paratype, dorsal

internal mould. N, NIGP149522, paratype, dorsal internal mould. O–X, Shuangheella elongata gen. et sp. nov. O, P, NIGP149523, para-

type, dorsal internal mould (O) and its latex cast (P). Q, R, NIGP149524, paratype, dorsal internal mould (Q) and its local enlarge-

ment (R) showing details of cardinalia and socket ridges. S, NIGP149525, paratype, dorsal external mould. T, NIGP149526, paratype,

dorsal external mould. U–X, NIGP149527, dorsal internal mould (U), its latex cast (W) and their local enlargement (V, X) showing

details of cardinal process, socket ridges and muscle field. Scale bars = 1 mm unless otherwise noted.


A B C D

E

I

F G H

J K L

M

Q

U V W X

R S T

N O P


1. Shell outline. Most shells are semielliptical in outline

(L/W ratio 0.66), with acute to rectangular cardinal

extremities; but some are subcircular (L/W ratio 0.89)

with rounded cardinal extremities.

2. Notothyrial platform and myophragm. Most dorsal

valves have a noticeably elevated notothyrial platform

and a low and broad myophragm, but in some speci-

mens the notothyrial platform is weak, and myo-

phragm is very faint (Fig. 9I, J, M, N).

3. Socket ridges. They vary from strong and high

(Fig. 8O–X) to thin and low (Fig. 9A–H). The distal

portion usually extends anterolaterally, but may

become subparallel to the hinge line in a few speci-

mens (Figs 8O, P, 9I, J, 11I, J, Q, R).

Remarks. Ochyromena plana gen. et sp. nov. occurs in the

silty mudstone of the upper Daguanshan Formation at

Shuanghe of Changning which was palaeogeographically

on the near-shore part of the Upper Yangtze Platform

(Fig. 1). It is quite abundant in the rocks together with

the other two new strophomenoids described in this

paper. Other major groups of brachiopods preserved in

the same horizon are less common. These include Pseudo-

lingula sp., Nothorthis perplexa Xu and Liu, 1984, Metor-

this sp., Taphrorthis guizhouensis (Xu and Liu, 1984),

Pseudomimella sp., and others.

Family RAFINESQUINIDAE Schuchert, 1893

Subfamily RAFINESQUININAE Schuchert, 1893

Genus SHUANGHEELLA gen. nov

Derivation of name. Shuanghe, type locality of the type species

of this new genus.

Type species. Shuangheella elongata gen. et sp. nov., upper Da-

guanshan Formation (lower to middle Dapingian), Shuanghe,

Changning County, southern Sichuan Province.

Diagnosis. Shell plano-convex to gently concavo-convex,

evenly multicostellate. Dental plates weak or absent. Ven-

tral muscle field lacking bounding ridges. Cardinalia

Type-B; bilobed cardinal process projecting antero-

ventrally; socket ridges extending antero-laterally; dorsal

muscle field inverted subtriangular.


Remarks. Most genera of the Rafinesquininae have a

concavo-convex profile, but the shell curvature of Shuan-

gheella gen. nov. is usually weak while the ventral valve is

slightly convex and the dorsal valve is nearly flat or gently

concave. Other characters of the rafinesquinids, such as

the multicostellate ornamentation, dorsal median ridge,

and transmuscle septa, are also absent in the new genus.

It is assigned to the family Rafinesquinidae mainly

because of its Type-B cardinalia. Hedstroemina Bancroft

(1929) from the Cheney Longville Flags (lower Caradoc,

Sandbian) of Shropshire, England, may develop nearly

even-sized costellae and similar cardinalia as in Shuanghe-

ella, but it differs from the new genus in having a larger

shell with a long dorsal geniculation, postero-lateral ru-

gae, and a smaller ventral muscle field. The unequal parvi-

costellae of Rafinesquina Hall and Clarke, 1892 may

become subequal in some specimens making their external

y = 0.7014x + 1.6374

R² = 0.6647

y = 0.2204x + 1.9547

R² = 0.5144

0

4

8

12

16

20

24

0 4 8 12 16 20 24

L/W

WMF/W

0

4

8

12

16

20

24Ochyromena plana gen. et sp. nov.dorsal valve: 14 specimens measured

mm mm

mm

L=W

WM

F=W

Shell width (W)

sh

ell le

ng

th (

L)

wid

th o

f m

uscle

fie

ld (

WM

F)

y = 0.179x-0.6947

R² = 0.9188

y = 0.0193x + 0.3481

R² = 0.1138

0

4

8

12

16

20

0 4 8 12 16 20

LC/L

HI/L

0

4

8

12

16

20

mm

mmmm Ochyromena plana gen. et sp. nov.dorsal valve: 14 specimens measured

Shell length (L)

Le

ng

th o

f ca

rdin

alia

(L

C)

He

i gh

t o

f d

ors

al in

tera

r ea

(H

I)

LC=L

HI=

L

B

A

F IG . 10 . A, B, Shell measurements of Ochyromena plana gen.

et sp. nov. All specimens from the upper Daguanshan Formation

(lower-middle Dapingian), Shuanghe. For abbreviations, see

Appendix S1.


A B C D

E

I

F G H

J K L

M

Q

U V W X

R S T

N O P

F IG . 11 . A–H, Primotimena globula gen. et sp. nov. A–D, NIGP149545, holotype, dorsal internal mould (A), its latex cast (C) and

their local enlargement (B, D) showing details of cardinal process, socket ridges and muscle field. E, F, NIGP149546, paratype, dorsal

internal mould (E) and its latex cast (F). G, H, NIGP149547, paratype, dorsal internal mould (G) and its latex cast (H). I–R, Ochyrom-

ena plana gen. et sp. nov. I–P, NIGP156513–156516, paratypes, dorsal internal moulds and their local enlargements (J, L, N, P). Q, R,

NIGP156517, paratype, dorsal external and internal moulds. S–X, Shuangheella elongata gen. et sp. nov. NIGP156518–156520, dorsal

internal moulds and their local enlargements (T, V, X). Scale bars = 1 mm unless otherwise noted.


A B C D

E

I

F G H

J K L

M

Q

U V W X

R S T

N O P

F IG . 12 . A, B, Shuangheella elongata gen. et sp. nov. NIGP156521, 156522, paratypes, dorsal internal moulds. C, I–N, Ochyromena

plana gen. et sp. nov. C. NIGP156523, paratype, dorsal internal mould. I–L, NIGP156529–156532, paratypes, dorsal external moulds.

M, N, NIGP156533, 156534, paratypes, ventral external moulds. D–H, Primotimena globula gen. et sp. nov. D, NIGP156524, paratype,

dorsal internal mould. E–H, NIGP156525–156528, paratypes, ventral internal moulds. O–X, Taphrorthis guizhouensis (Xu and Liu,

1984). O, P, NIGP156535, dorsal internal mould and its local enlargement (P) showing details of cardinalia and muscle field. Q–T,

NIGP156536–156539, dorsal internal moulds with one of the specimens (R) showing clearly impressed muscle field and narrowly

divergent vascula media. U, V, NIGP156540, 156541, ventral internal moulds. W, X, NIGP156542, 156543, dorsal external moulds.

Scale bars = 1 mm unless otherwise noted.


appearance similar to the new genus, but its prominent

dorsal transmuscle ridges are not known in Shuangheella.

The two rafinesquinids, Pentagomena and Heteromena

described by Zhan and Jin (2005a) from the lower Dashaba

Formation (lower Darriwilian), which overlies the Daguan-

shan Formation of the same section, differ from the new

genus in having larger shells with irregular concentric ru-

gae, strongly unequal parvicostellae, prominent dental

plates, and a different ventral muscle field.

Shuangheella elongata sp. nov.

Figures 3C, 4B, E, H, K, 9O–X, 11S–X, 12A, B, 13A–O

Derivation of name. Latin, elongatus, prolonged, referring to the

longitudinally semielliptical shell of this species.

Type specimens. Holotype, NIGP149528; paratypes, NIGP-

149523–149527, 149529–149532, 156521, 156522, from the upper

Daguanshan Formation (lower to middle Dapingian), Shuanghe,

Changning, southern Sichuan.

Material. One ventral internal, 11 dorsal internal and five dorsal

external moulds, upper Daguanshan Formation (lower to middle

Dapingian), Shuanghe, Changning, southern Sichuan.

Diagnosis. Shell medium-sized, subcircular, planoconvex

to gently concavoconvex, evenly multicostellate, with

incipient pseudodeltidium and chilidium. Dental plates

absent. Ventral muscle field weakly impressed, lacking

bounding ridges. Notothyrial platform absent. Cardinalia

Type-B; two cardinal process lobes projecting antero-ven-

trally, separate and divergent from bases; socket ridges

extending antero-laterally; dorsal muscle field inverted

subtriangular in outline, bearing wide myophragm.

Description. Shell medium-sized, longitudinally semielliptical to

subcircular in outline, with average length/width ratio of 0.80

(see Appendix S1). Dorsal valve usually flat, gently concave in

small number of specimens. Ventral valve evenly and moderately

convex. Anterior commissure rectimarginate. Maximum width at

or slightly anterior of hinge line; cardinal extremities rectangular

or rounded. Ventral interarea planar, apsacline, with height

equal to 12 per cent length of shell; pseudodeltidium thin, mod-

erately convex, covering posterior half of delthyrium; dorsal in-

terarea planar, hypercline, with height equal to 4 per cent length

of valve; chilidium thin, covering posterior part of notothyrium.

Multicostellae fine, increasing anteriorly by intercalation, averag-

ing seven per 1 mm.

Teeth small, wedge-shaped, with rounded crest; dental plates

absent. Muscle field rhomboidal in outline, about 34 per cent

length and 38 per cent width of shell, lacking surrounding

ridges; adductor scars very small, subtriangular in outline,

located in posteromedian part of muscle field, separated from

diductor scars by weak ridges; diductor scars also subtriangular,

with their longitudinal axes diverging at about 30 degrees. Man-

tle canal system not observed.

Cardinalia occupying 13 per cent length and 28 per cent

width of valve; notothyrial platform poorly developed or absent;

cardinal process lobes projecting antero-ventrally from hinge

line, with plate-like shaft and swollen myophore; bases of cardi-

nal process lobes discrete and slightly divergent from each other

(Fig. 4B, E, H, K). Socket ridges straight, short, low, diverging

from each other antero-laterally at 90–100 degrees, not fused to

cardinal process medially (Figs 4B, E, H, K, 13A–D, I–L). Sock-

ets open antero-laterally, without outer ridges or socket plates.

Muscle field broadly inverted subtriangular in outline, about

29 per cent length and 34 per cent width of valve, bearing low,

wide and anteriorly tapering myophragm, lacking transmuscle

ridges; posterior pair of adductor scars subcircular, widely sepa-

rated; anterior pair longer but narrower, longitudinally elliptical.

Mantle canal system saccate, poorly impressed; vascula media

originating from anterior ends of anterior adductor scars,

extending anteriorly for short distance before turning and multi-

branching; some very weak ridges in area of vascula genitalia.

Ventral and dorsal valves often with peripheral rims at about

85 per cent and 90 per cent of shell length, respectively.

Remarks. Longitudinally semielliptical shell outline with

length/width ratio up to 0.98 and densely populated and

evenly sized and spaced multicostellae are two distin-

guishing characters of the new species. Its notothyrial

platform is usually absent, but the notothyrial area is

weakly elevated and merges anteriorly with the low med-

ian elevation between adductor muscle scars of both sides.

It is not a real myophragm but confined to the muscle

field. Its non-differentiated shell ornamentation, undevel-

oped dental plates and dorsal muscle field without any

bounding and transmuscle ridges suggest that this new

species is a primitive form of rafinesquinid, which is con-

sistent with its early biostratigraphical occurrence.

Family GLYPTOMENIDAE Williams, 1965

Subfamily GLYPTOMENINAE Williams, 1965

Genus PRIMOTIMENA gen. nov

Derivation of name. Latin, primotinus, original, early, with refer-

ence to the primitive nature of the new genus for glyptomenids.

Type species. Primotimena globula gen. et sp. nov., upper Da-

guanshan Formation (lower to middle Dapingian), Shuanghe,


Diagnosis. Shell nearly planoconvex, multicostellate. Den-

tal plates short, thin. Cardinalia Type-C; cardinal process

lobes small, projecting postero-ventrally. Socket ridges

thin, short, straight. Dorsal muscle field subtriangular in

outline, lacking transmuscle ridges.


A B C D

E

I

F G H

J K L

M

Q

U V W X

R S T

N O P



Remarks. This genus is established based on a combination

of external and internal characters: plano- to gently conc-

avo-convex lateral profile; almost evenly sized and spaced

multicostellae; well-developed dental plates; relatively large,

triangular ventral adductor scar; two pillar like cardinal

process lobes entirely beyond hinge line (Fig. 4C, F, I, L);

thin, low and short socket ridges normally without lateral

distal extensions. In North America, there are some early

glyptomenids of late Darriwilian age, such as Glyptomena

Cooper, 1956, Pionomena Cooper, 1956, and Teratelasma

Cooper, 1956. The four species of Glyptomena described by

Cooper (1956) have strongly unequal parvicostellae, ventral

adductor enclosed completely by diductor scars in most

forms, and socket ridges widely divergent, with distal ends

subparallel to the hinge line. Pionomena has a gently bicon-

vex shell, irregularly differentiated multicostellae, and nearly

obsolescent dental plates. Teratelama differs from the new

genus in having strong, well-developed transmuscle ridges,

and strong dorsal myophragm and median ridge (Cooper

1956; Cocks and Rong 2000). Some shells of Hesperinia sin-

ensis resemble the new genus in its flat dorsal valve and

poorly differentiated parvicostellate ornamentation (Rong

et al. 1999), but differ in their dorsal interiors. Hesperinia

has typical Type-A cardinalia with a pair of stout, strongly

posteriorly extended cardinal process lobes, and generally

postero-laterally extending brachiophores. Here we follow

Rong et al. (1999) to treat it as a strophomenid genus rather

than a glyptomenid as did Cocks and Rong (2000). But,

Primotimena is treated as the earliest known representative

of glyptomenid because of its Type-C cardinalia.

Primotimena globula sp. nov.

Figures 3B, E, 4C, F, I, L, 11A–H, 12D–H, 13P–X, 14

Derivation of name. Latin, globulus, ball, spherical; with refer-

ence to the subcircular outline of this species.

Type specimens. Holotype, NIGP149545; paratypes, NIGP-

149533–149544, 149546, 149547, 156524–156528, from the upper

Daguanshan Formation (lower to middle Dapingian), Shuanghe,


Material. Twelve ventral internal, eight dorsal internal and six

dorsal external moulds from the upper Daguanshan Formation

(lower to middle Dapingian), Shuanghe, Changning, southern

Sichuan.

Diagnosis. Shell nearly plano-convex to gently concavo-

convex, multicostellate,with incipient pseudodeltidium

and chilidium. Dental plates short, thin, extending anteri-

orly as bounding ridges of muscle field. Two small lobes

of cardinal process projecting postero-ventrally with

inflated crests, located entirely posterior of hinge line.

Socket ridges thin, short, straight, merging medially with

cardinal process bases. Notothyrial platform lacking. Dor-

sal muscle field subtriangular in outline, without trans-

muscle ridges.

Description. Shell medium-sized, subcircular to longitudinally

semielliptical, with average length/width ratio 0.87 for ventral

valve and 0.78 for dorsal, widest along hinge line or slightly

anterior of it; planoconvex to weakly concavoconvex. Cardinal

extremities rectangular to rounded. Anterior commissure recti-

marginate. Ventral interarea planar, apsacline, with height equal

to about 12 per cent length of shell; delthyrium small, covered

by gently convex pseudodeltidium. Dorsal interarea planar, ana-

cline, about 5 per cent as high as dorsal length; notothyrium

posteriorly covered by incipient chilidium. Multicostellae nearly

evenly spaced, 3–4 per 1 mm, increasing anteriorly by both

intercalations and bifurcations; size differentiation of costellae

inconspicuous, about four finer costellae between two slightly

coarser ones. Concentric lamellae very weak, sparse, usually

developed in shell anterior half.

Teeth stout, wedge-shaped. Delthyrial cavity small, deep

(Figs 3B, E, 13V, 14D, F); lateral cavities narrow, deep (Figs 3B,

E, 12E, H, 13Q–X). Dental plates thin, short, normally with

short anterior extensions serving as postero-lateral bounding

ridges of muscle field. Muscle field elongate-oval, about

34 per cent length and 30 per cent width of shell, without ante-

ro-lateral bounding ridges or inner ridges; adductor scar subtri-

angular in outline, located in posteromedian part of muscle

field, slightly deeper than diductor scars; diductor scars elon-

gated subtriangular in outline, longer than adductor scar, with

F IG . 13 . A–O, Shuangheella elongata gen. et sp. nov. A–D, NIGP149528, holotype, dorsal internal mould (A), its latex cast (C) and

their local enlargement (B, D) showing details of cardinal process, socket ridges and muscle field. E, F, NIGP149529, paratype, ventral

(left) and dorsal (right) internal moulds (E) and enlargement of the dorsal one (F). G, H, NIGP149530, paratype, dorsal external

mould (G) and its local enlargement (H) showing details of evenly sized and spaced multicostellae. I–L, NIGP149531, paratype, dorsal

internal mould (I), its latex cast (K) and their local enlargement (J, L) showing cardinal process, socket ridges and muscle field. M–O,

NIGP149532, paratype, dorsal external mould (M), its local enlargement (N) and latex cast (O). P–X, Primotimena globula gen. et sp.

nov. P, NIGP149533, paratype, ventral internal mould. Q, R, NIGP149534, paratype, ventral internal mould (Q) and its local enlare-

ment (R) showing details of lateral cavities, dental plates, and muscle field. S, T, NIGP149535, paratype, ventral internal mould (S)

and its local enlargement (T) showing details of dental plates and muscle field. U–X, NIGP149536, paratype, ventral internal mould

(U), its latex cast (W) and their local enlargement (V, X) showing details of psedudodeltidium, delthyrial cavity, lateral cavities, teeth,

dental plates, and muscle field. Scale bars = 1 mm unless otherwise noted.


A B C D

E

I

F G H

J K L

M

Q

U V W X

R S T

N O P


two lobes subparallel or diverging anteriorly at very small angles.

Mantle canal system poorly impressed; vascula media originating

from both anterior ends of diductor scars, extending subparallel-

ly for a short distance before branching; vascula genitalia not

observed.

Cardinalia occupying 11 per cent length and 25 per cent

width of valve; notothyrial platform poorly developed or absent

(Figs 4C, F, I, L, 11A–H, 14Q–S, U–X,); two cardinal process

lobes small, separated by deep groove; each lobe with pillar-like

shaft and swollen, longitudinally grooved myophore (Fig. 14T,

X), projecting postero-ventrally, positioned entirely beyond

hinge line. Socket ridges short, thin, diverging from each other

at about 95 degrees, medially fused with bases of cardinal pro-

cess, extending antero-laterally. Sockets narrow, shallow, open

antero-laterally. Muscle field V-shaped, about 27 per cent length

and 29 per cent width of valve, lacking bounding and transmus-

cle ridges; two pairs of adductor scars divided by medial eleva-

tion: posterior pair subcircular, just anterior of distal ends of

socket ridges, slightly deeper than anterior pair; anterior pair

subcircular or longitudinal oval, slightly smaller than posterior

pair. Myophragm weakly developed, originating from notothyrial

cavity, widest at level of distal ends of socket ridges, then taper-

ing anteriorly to anterior margin of muscle field. Mantle canal

system saccate, poorly impressed; vascula media originating from

both anterior ends of anterior pair of adductor scars, extending

anteriorly subparallel to each other before branching at about

two-thirds length of shell.

Peripheral crenulations on valve interior usually extending up

to 10 per cent length of shell, but occupying nearly entire shell

interior (except muscle field and vascula genitalia) in some spec-

imens (e.g. Fig. 11A–D).

Remarks. Two other glyptomenid species occur in the

overlying Dashaba Formation of the same section (about

10 m, or two graptolite biozones, above the horizon of cur-

rent species), Glyptomena? rugulosa Zhan and Jin (2005a, p.

46, pl. 11, figs 16, 17, pl. 12, figs 2–4, 7–9) and Glyptomena

sp. A Zhan and Jin (2005a, p. 45, pl. 14, fig. 15, pl. 15,

figs 1–9, 14), both of which are distinguishable from

Primotimena globula in having strongly differentiated parv-

icostellae and variably developed concentric rugae. Their

ventral and dorsal interiors are also quite different from

those of Primotimena globula gen. et sp. nov.

Order ORTHIDA Schuchert and Cooper, 1932

Superfamily ORTHOIDEA Woodward, 1852

Family ORTHIDAE Woodward, 1852

Genus TAPHRORTHIS Cooper, 1956

Taphrorthis guizhouensis (Xu and Liu, 1984)

Figures 12O–X, 15A–E, I, J

1984 Multicostella guizhouensis Xu and Liu, p. 184, pl. 6,

figs 3, 4, 10–12.

1984 Multicostella obesa Xu and Liu, p. 185, pl. 6, figs 1,

2, 5–7, 9.

Material. Four ventral external and five internal, six dorsal

external and 13 internal moulds.

Remarks. The cardinalia and ventral interiors of the two

species assigned to Multicostella Schuchert and Cooper,

1931 by Xu and Liu (1984) are more typical of Taphrorthis

Cooper, 1956. Their material was collected from the upper

Meitan Formation (Dapingian to lower Darriwilian) of

Tongzi, northern Guizhou, about 150 km east of the study

area of this paper (Fig. 1). Specimens from the Daguan-

shan Formation have external and internal characters

similar to the Tongzi species, such as a longitudinally

semielliptical shell with multicostellate ornamentation, an

elongated ventral muscle field that may be bilobate in

some specimens, a small, thin, plate-like cardinal process

confined to the notothyrial cavity which is slightly elevated

by the clearly developed notothyrial platform, short bra-

chiophore supports merging antero-medially to continu-

ous with thick and low median ridge, all of which are

typical of Taphrorthis. In our collection, this species is the

fourth most abundant brachiopod constituent except for

the three strophomenoids described above. Some popula-

tion variations could be observed, particularly the

development of cardinalia including the cardinal process,

brachiophores, brachiophore supports and notothyrial

platform, and the dorsal median ridge substantially

variable between individuals (see those figured specimens).

F IG . 14 . A–X, Primotimena globula gen. et sp. nov. A, B, NIGP149537, paratype, ventral internal mould (A) and its local enlarge-

ment (B) showing details of dental plates and muscle field. C, D, NIGP149538, paratype, ventral internal mould (C) and its local

enlargement (D) showing details of dental plates and muscle field. E–H, NIGP149539, paratype, ventral internal mould (E), its latex

cast (G) and their local enlargement (F, H) showing details of pseudodeltidium, teeth, dental plates, and muscle field. I, M, N,

NIGP149540, paratype, dorsal external mould (I), its latex cast (M) and local enlargement (N) showing details of multicostellae. J–L,

NIGP149541, paratype, dorsal external mould (J), its latex cast (K) and local enlargement (L) showing details of multicostellae. O, P,

T, NIGP149542, paratype, dorsal internal mould (O), its latex cast (P) and local enlargement (T) showing details of cardinal process

and socket ridges. Q–S, NIGP149543, paratype, dorsal internal mould (Q), its latex cast (R) and local enlargement (S) showing details

of cardinal process, socket ridges and muscle field. U–X, NIGP149544, paratype, dorsal internal mould (U), its latex cast (W) and their

local enlargement (V, X) showing details of cardinal process, socket ridges, and muscle field. Scale bars = 1 mm unless otherwise

noted.


Family NANORTHIDAE Havl�ı�cek, 1977

Genus NOTHORTHIS Ulrich and Cooper, 1938

Nothorthis perplexa Xu and Liu, 1984

Figures 8B, 15L

1984 Nothorthis? perplexa Xu and Liu, p. 171, pl. 11, figs

22–25.

Material. One ventral and one dorsal internal moulds.

Remarks. Xu and Liu (1984) reported the species from

the lower Meitan Formation (Floian) of Yanhe, northeast-

ern Guizhou. The Daguanshan specimens are larger in

size, and slightly younger in age (from lower Dapingian

beds of the upper Daguanshan Formation), but both of

them have a semicircular outline, multicostellae, a small

cardinal process confined to the posterior end of notothy-

rial cavity, and a pair of short, thin and divergent bra-

chiophores.

Superfamily PLECTORTHOIDEA Schuchert in Schuchert and

LeVene, 1929

Family PLECTORTHIDAE Schuchert in Schuchert and LeVene,

1929

Genus PSEUDOMIMELLA Xu and Liu, 1984

Pseudomimella sp.

Figure 15F, G

Material. One dorsal internal mould.

Remarks. The dorsal valve is strongly convex, almost glob-

ular, and about 7–8 mm in length and width. Its cardinalia

includes a thin plate-like cardinal process confined to the

posteromedian part of the notothyrial cavity, a pair of thin

and low brachiophores diverging at about 120 degrees, and

a weakly but clearly elevated notothyrial platform which is

continuous with the low and wide myophram. Adductor

muscle scars are clearly impressed, and inverted trapezoidal

in outline; posterior pair larger and slightly deeper than the

A B C D

E F G H

I J K L

F IG . 15 . A–E, I, J, Taphrorthis guizhouensis (Xu and Liu, 1984). A, B, NIGP156544, 156545, ventral external moulds. C–E, I, J,

NIGP156546–156548, 156551, dorsal internal moulds, and local enlargement (J) showing the damaged cardinalia. F, G, Pseudomimella

sp., NIGP156549, dorsal internal mould and its local enlargement showing details of cardinalia and muscle field. H, Neseuretus concav-

us Lu, NIGP156550, cranidium of an adult trilobite. The occurrence of this trilobite at the Collection AFI57d indicates a Dapingian to

earliest Darriwilian age for the rocks and a shallow water benthic regime for the living environmental background (Z. Zhou, pers.

comm. 2012) which further supports the inference made by Zhan et al. (2006) according to their synecological analysis for brachio-

pods. K, Camerellid gen. et sp. indet., NIGP156552, ventral internal mould. L, Nothorthis perplexa Xu and Liu, 1984, NIGP149507,

ventral internal mould. Scale bars = 1 mm unless otherwise noted.


anterior pair. The type species of this genus, Pseudomimella

formosa (Wang, 1955) (Xu and Liu 1984, p. 180, pl. 5, figs

21–23, 25–32) from the Dawan Formation and its equiva-

lents on the Upper Yangtze Platform, is similar to our pres-

ent material but with stronger brachiophore bases and

cardinal process continuous anteriorly with the strong

myophragm. They might be conspecific, but we are not

confident with just one specimen. The valve shape, cardi-

nalia and muscle field are reminiscent of Xinanorthis,

which is common in the Floian rocks of South China but

usually has a stronger cardinal process.

Order PENTAMERIDA Schuchert and Cooper, 1931

Superfamily CAMERELLOIDEA Hall and Clarke, 1895

Family CAMERELLIDAE Hall and Clarke, 1895

Camerellid gen. et sp. indet.

Figure 15K

Remarks. One internal mould probably represents a ventral

valve of a camerellid on the basis of its elongated ontline

and a very weak median sulcus, but no spondylium or med-

ian septum is visible. It is about 3.1 mm long and wide with

its widest position at about two-thirds of shell. About

3 weak costae on both slopes. At the same section, another

dorsal internal mould of a camerellid, Maydenella sp. (Zhan

and Jin, 2005a, p. 48, pl. 16, figs 6, 7) was reported from the

basal Dashaba Formation (lower Darriwilian). Stratigraphi-

cally, it is a continuous section and it is about 10 m above

the horizon where the current specimen is collected.

Acknowledgements. Chen Xu, Zhou Zhiyi, Wang Yi, Zhang

Yuandong, Liu Jianbo, and Cheng Jinhui helped in several seasons

of field work. Zhou Zhiyi identified the trilobite specimens, and

Zhang Yuandong provided data on graptolite biostratigraphy.

Gudvig Baarli provided some stratigraphical information about

western European species, particularly species from Estonia. The

constructive criticism and careful editing by the two reviewers,

Enrique Villas and Ian Percival, and the journal Editor Fernando

Alvarez, greatly helped improve the clarity of our discussions.

Financial supports for this project are from the National Natural

Science Foundation of China (40825006, 41221001, 41290260),

and the State Key Laboratory of Palaeobiology and Stratigraphy

(LPS). This paper is a contribution to the IGCP project 591

‘The Early to Middle Paleozoic Revolution’.

Editor. Fernando Alvarez

SUPPORTING INFORMATION

Additional Supporting Information may be found in the online

version of this article:

Appendix S1. Statistical data of shell measurements.

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The earliest known strophomenoids (Brachiopoda) from early Middle Ordovician rocks Of South China