A new species of permianellids (Brachiopoda): Taxonomic and palaeoecologic significance

A NEW SPECIES OF PERMIANELLIDS (BRACmOPODA):TAXONOMIC AND PALAEOECOLOGIC SIGNIFICANCE

SHUZHONG SHEN , BINGHENG

FAN,

CHUAN

ZHANG &

X!AoPING

ZHANG

SHEN S., FAN B., ZHANG C. & ZHANG X.. 1994. A new species of Permianellids (Brachiopoda) : taxonomic and palaeoecologic significance. [Une nouvelle espece de Brachiopode Perrnianellide : implicati on taxonomique et paleoecologique .l GEOBIOS, 27,4 : 477-485. Villeurbann e Ie 30.08.1994. Manuscrit depose le 24.02.1993 ; accepte definitivement le 04.03.1993 .

ABSTRACT

Until recently the study of Permianellids was neglect ed. Thi s paper describes a new species of permianellids brachiopod from limestones of the Changhsing Formation of the uppermost Permian in the Nantong Mining Area Sichuan Province of South China. Based on detailed stu dies of the external and internal shell morphology, shell fabric and presumed living habits of the species, the writers consider in many respects the Permianellids have affinity to the oldhaminids and may be treated as a family. The analyses of th e attachment pattern, population characteristics and associated faunas show that this group belongs to higher epizoan suspension feeders in the soft substrate community near normal wave base. KEY-WORDS : PERMIANELLIDS , OLDHAMINIDS , BRACHIOPODS , PERMIAN, PALAEOE COLOGY

RESUME

-Iusqu'a une date recente, l'etude des brachiopodes permianellides a ere neglige e. Cet article decrit une nouvelle espece des calcaires de la Formation de Changhsing du Permien superieur du District mini er de Nantong, Province de Sichuan, Chine du Sud. A partir de l'etude detaillee de la morphologie intern e et externe de la coquille , de sa structure et du mode de vie suppose, les auteurs considerent que , par beau coup d'aspect, les Permianellidss ont des affinites avec les Oldhaminides et peuvent etre consideres comme une famille a part. L'analyse des processus d'attachement, des caracteristiques populationnelles et la faune associee montrent que ce groupe appartient aux epizoaires suspensivores les plus eleves dans une communaute sur substrat meuble pres de Ia base d'action des vagues. MOTS-CLES : PERMIANELLIDES, OLDHAMINIDES, BRACHIOPODES, PERMIEN, PAL f~OECOLOGIE.

INTRODUCTION Permianellids are so peculiar in shape and structure that some brachiopodologists were puzzled while studying them. Over the past decade there has been a large increase in data published on fossil permianellids. Permianellid fossils have been found in Afghanistan, Thailand, Japan, Inner Mongolia and many localities of South China. Their ages range from the Sakamarian to the Changhsingian. Hitherto six different scheme s related to the systematic position of permianellids have been proposed. The main reason leading to confusion in permianellid classification is that specimens are usually preserved in a very

bad state, most are fossil molds and casts, so their internal structures cannot be studied. In addition, some researchers lacked a complete understanding of the relationship between permianellids and other brachiopods, especially the relationships of the permianellids to the oldhaminids. Over several years of work on the uppermost Permian brachiopods in southwestern China we collected about one hundred specimens of permianellids from limestones of the Changhsing Formation in the Nantong Mining Area, of which 87 specimens are well preserved. Based on studies of these specimens and critical remarks from Dr. Richard E. Grant we have updated knowledge of permianellids. The present paper is an attempt to give a more objective discussion of this group.

478

External features

elongated, symmetrical (PI. 1, fig. 1) or asymmetrical (PI. 1, fig. 11). Both valves are flat in longitudinal profile, but concave-convex or plano-convex in transverse profile. The maximum width is generally located at the anterior part of the shell. The ventral valve is separated into two lobes at the anterior by a deep incision but is connected end posteriorly. The incision occupies more than half of the shell length. The posterolateral sides are diverging at about 20°_30°, but the antero- lateral sides are almost parallel.

The present species has a grotesque shape. General outline is bilobate, the two lobes are greatly

The posterior part of the ventral valve usually has an attachment ring by which these permia-

SYSTEMATICS AND DESCRIPTIONS Suborder OLDHAMINIDINA Williams, 1953 Superfamily LYTTONIACEA Waagen, 1883 Family PERMIANELLIDAE He & Zhu, 1979 Genus Laterispina WANG & CHING, 1991

LATERISPINA PARALLELA 1-12 ; PI. 2, figs. 1-11, 14.

SP. NOV. :

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Figure 1 - Section of Laterispina parallela (sp, nov.), Dorsal valve top, looking posteriorly, distance from ventral umbonal tip indicated in mm. x 3. Sections transversales dans La coquille de L. parallela (nov. sp.). Valve dorsale uers le haut, en vue posterieure ; distance a l'exiremite du crochet exprimee en mm.

479 c.pr,

a.r.

i. s.

s. f.

Figure 2 - Morphological reconstruction of Laterispina parallela (After Wang & Ching 1991 ; emended by authors). a.r., attachment ring; t., tooth; m.s., median septum; c. pl., central platform; i.s., internal septum; c. pr., cardinal process; s., socket; b.p., brachiophore process; l.r., longitudinal ridge; f., flange; Po. view of ventral interior; B, view of dorsal interior. Reconstitution de l'interieur des valves de Laterispina parallela. a.r., anneau de fixation; t., dent; m.s., septum median; c. pl., plateforme centricale ; i.s., septum interne; c.pr., processus cardinal ; s., fossette; b.p., processus du brachiophore ; l.r., crete longitudinale ; f, rebord. A, vue de l'interieur ventral; B, vue de l'interieur dorsal.

nellids attached to crinoid stems. Its internal diameter is 3-6 mm and the external diameter is 6.5-8 mm. The median sulcus originates at the umbonal region and widens anteriorly. The hinge is typically lyttoniid. A short and straight hinge line and two small ears at the extremities are visible from the dorsal side (PI. 1, fig. 11). The dorsal valve is slightly concave or flat. The beak is inconspicuous but there is a conical process on the umbonal region (PI. 1, figs. 10, 11). The shell surface is smooth except for a few prominent growth lines. Many small circular lines can be seen under the stereomicroscope, numbering 11 per 2 mm, which are arranged linearly along the concentric lines. The front lateral regions of the ventral valve have fence-shaped margins (PI. 1, figs. 5,1 ; Fig. 3). The posterior end of each lobe has an acute longitudinal ridge (Fig. 1,4.2-3.4).

Internal structures He & Zhu (1979) and Wang & Ching (1991) considered that permianellids possessed teeth and sockets, whereas Mu & Liu (1989) and Yang (1984) thought that they lacked them. Careful observation of the type specimens and the figures reported by Wang & Ching confirmed the existence of two degenerate teeth (Wang & Ching 1991 : PI. 2, fig. 6) and two ovally triangular sockets (He & Zhu 1979 : PI. 1, fig. 1b). The interior of the ventral valve has a longitudinal, hollow central platform as wide as the sulcus, probably developed from the median lobe of the valIum of oldhaminids. Its cross sections are trapezoidal in shape anteriorly (PI. 2, fig. 2), triangular posteriorly (PI. 2, figs. 7,8). No previously published papers report any internal structures within the central platform. Systema-

tic sections of the specimens from the Nantong Mining Area prove the presence of complicated internal structures. The platform within the pseudopunctate layer possesses one to three irregular horizontal or oblique internal septa (PI. 2, figs. 1,9). The form of these septa may not have significance for distinction of species within the permianellids. An oblique median septum is well developed on the central platform. Generally its anterior part is knife-edged, but the top of the posterior part is strongly thickened to support the weight of the dorsal valve (PI. 2, fig. 6 ; Fig. 1). Musculature is probably asymmetrical, located on the right side (Fig. 1,3.8,3.4). The interior of the dorsal valve has a spherical bilobate cardinal process formed from the convergence of the two inner socket ridges in the cardinalia. Cross sections reveal that the dorsal valve possesses two strong brachiophore processes similar to the crura of rhynchonellids. The brachiophore processes are 1-4 mm long, unequally develped and asymmetrically disposed, extending forward to the pedicle cavity (PI. 2, figs. 4, 6 ; Fig. 1, 2b). Each lobe has a longitudinal ridge extending from the posterior to near the anterior commissure on the middle, and a flange on the lateral margin (PI. 1, figs. 2,9 ; Fig. 2b).

Shell fabric Both valves of the new species are composed of two layers, of which the inner is a laminar layer, occupying about 1/2 to 1/5 of the shell thickness and the outer is a pseudopunctate layer (PI. 2, Fig. 10). The pseudopunctae do not extend through the laminar layer, and are about 7-14 urn in diameter (PI. 2, figs. 1,11). Liang (1990) considered that the permianellids possess both pseudopunctae and punctae, but he did not give

480 any proofs in his book. We recognize that the permianellid pseudopunctae are different from the punctae of the terebratulids (PI. 2, figs. 12, 13). Perhaps Liang mistook the pseudopunctae for punctae.

Measurements (in mm). CHNT9054(holotype) CHNT9020 CHNT9058 CHNT9056 CHNT9061 CHNT9023 CHNT9027 CHNT9067 CHNT9063 CHNT9089

length 98,0 50.0 62.7 65.5 >50 .0 >52.0 86.0 >32.4 >41.2 >38.8

widthfmax) 25 ,0 23.0 23.1 21.0 22.0 21.0 13.0 17.3 16.0 16.3

thickness 5.8 ? ? ? ? ? ? ? 3.0 ?

Occurrence All specimens were collected from the uppermost part of the Changhsing Formation in the Nantong Mining Area of Sichuan Province , South China.

COMPARISONS AND DISCUSSIONS Permianellid fossils were first described by Termier et al in 1974, named Dicystoconcha and assigned to the Family Lyttoniidae Waagen , 1883 of Oldhaminidina Williams 1953. After then, several authors proposed some genera based on their own specimens and referred them to different orders. He & Zhu (1979) proposed the new order Permianellida according to their studies on

the specimens from Jiangxi in southeastern China. Liang (1982) described some permianellid specimens from the Middle Permian in Chekiang Province, proposed the new genus Dipunctella and assigned it to Productacea Gray 1840 It is interesting that Liang (1990) proposed a new suborder Dipunctellinina including two new superfamilies and five families following his studies of the permianellids. On the basis of a comparison between the permianellids and Falafer GRANT, 1972 ; Yang (1984) established the Genus Guangjiayanella and placed it in the Family Cooperinidae Paj aud 1968 of the Strophalosiacea Schuchert 1913 Mu & Liu (1989) studied a dozen of permianellid fossils from the Maokouan near Guangzhou City (Guangdongina) . They introduced the Superfamily Permianellacea He & Zhu and placed them in the Terebratulida Moore 1952. Based on a study of shell shape, ornamentation, interior structure and shell fabric of the permianellids, Wang & Ching (1991) treated them as an independent family (Permianellidae He & Zhu) and assigned them to Oldhaminidina Williams 1953. The differences between the permianellids and the tereberatulids are that the former have pseudopunctate shells and the complicated central platform, whereas the latter possess endopunctate shells and a loop. Mu & Liu '1989) placed the permianellids in the Terebatulida for two important reasons : the presence of incurved hinge line and the well-developed palintrope. Their specimens , preserved in mudstones, are all interior casts. Therefore, no ears could be preserved and the palintrope looks well developed. The permia-

PLATE 1 Fig. 1-12 . Laterispina parallela, nov. sp. : 1, vent ral view, holotype, CHNT9054 x 1, showing the double-belted shape, attachment ring and fence. 2, interior view of a dorsal valve, CHNT9020 x 2, showing the longitudinal ridge in the middle lobe and the flan ge in the lateral margin. 3, a print of specimen, CHNT9058 x 1. 4, dorsal view of an incomplete specimen, CHNT9056 x 1. 5 , vent ral view of a fragment of vent ral va lve, CHNT9025 x 2, showing the fence on the lateral surface . 6 , extern al surface of a dorsal valve, CHNT9061 x 1, showing the concentric lines. 7, external mold of an incomplete specimen, CHNT9023 x 1. 8, vent ral view of an incomplete specimen, CHNT9027 x 1. 9, interior view of a dorsal valv e, CHNT9067 x 1, showing two longitudinal ridges. 10, dorsal view of an incomplete specimen, CHNT9022 x 1, showing a conical process on the umbonal region. 11, dorsal view of an asymmetrical specimen, CHNT9063 x 2, showing the attachment ring, two small ears and the short and straight hinge line . 12, ventral view of specimen, CHNT9089 x 2. 1, vue uenirale, holotype, montrant la forme en double vourroie, l'anneau d'attachement et le bourrelet. 2, vue interne d'une valve dorsale montrant la crete longitudinale dan s le lobe median et le bourrelet du bord lateral. 3, vue generale. 4, vue dorsale d 'un specimen incomplet. 5, vue ventral e d 'un fragment de valve ventrale montrant et le bourrelet de la surface laterale. 6, surface externe d'une valve dorsale montrant les lignes concentriques. 7, moule externe d'un specimen incomplet. 8, vue ventrale d'un specimen incomplet. 9, vue interne d'une valve dorsale montrant les deux cretes longitudinales. 10, vue dorsal e d'un. specimen incomplet montrant un pr ocessus conique dans la region umbonale. 11, vue dorsal e d'un. specimen asymetrique montrant l'anneau d'atta chem ent, deux petites oreillettes et la charniere courte et droite. 12, vue ventrale du specimen. All specimens described in this paper are preserved in the Department of Geology, China University of Mining & Technology. Les specimens decrits dans cette note sont deposes au Department of Geology, China Univ ersity of Mining & Technology.

Geobios n° 27, fase. 4

Pl.} S. Shen, B. Fan, C. Zhang & X. Zhang

482 nellids, except for the slightly similar concavoconvex cavity and the strong sulcus, are totally unrelated to the Genus Falafer because the latter is a spinose strophalosiid. Permianellids seemingly resemble productids in having a concavo-convex shell cavity and the pseudopunctate shell. However, they lack hollow spines on the surface of the shell and inner spines in the shell , which are the most important characters possessed by productids. Laterispina WANG & CHING, 1991 has a fence-shaped marginal brim on the ventral valve , but completely different from productid spines since the fences do not penetrate the shell and may be rolled up by the marginal brim. Detailed comparisons indicate that the permianellids have affinity to the oldhaminids in many respects including the distinctive hinge region, the short and straight hinge-line, the concavoconvex cavity, the highly specialised shape and outline, the pseudopunctate shell and the lack of spines. The habit of living attached to crinoids is also well reported in the Superfamily Lyttoniacea Waagen 1883 (e.g. Wanner & Sieverts 1935 : p. 243, 248 ; pl. VI-IX ; Stehli 1954 : pl. 19, fig. 1 ; Cooper & Grant 1974 : pl. 127, figs. 19-21 ; pl. 164, figs. 9-11 ; Grant 1976 : p. 166, pl. 30, figs. 19-23 etc). So it is normal to assign the permianellids to the Lyttoniacea. Nevertheless, we think the following characters including the bilobate shape, the total lack of a septal apparatus, the possession of the complicated central platform in the ventral valve, the strong brachiophore processes in the dorsal valve and the pseudopunctatae

of both valves indicate differences between the permianellids and the existing families of Lyttoniacea. Therefore we treat the permianellids as a Family and the family Permianellidae He & Zhu is retained. Laterispina differs from Permianella and Dicystoconcha in having a complicated fence-shaped margin. Up to now one species from Guangxi Procince (L. liaoi WANG & CHING, 1991) was described in this genus. The main differences between the present new species and L. liaoi are that the latter has a triangular outline and an umbonal angle of about 55°, but the former has an elongately double-belted outline and a smaller umbonal angle (about 20°_30°).

PALAEOECOLOGY AUTECOLOGY All of the permianellids, like many lyttoniids, were attached throughout life, fixed to foreign objects by their posterior attachment ring (Fig. 3). Continuous sections reveal that the fabric of the attachment ring (pseudopunctate) is completely different from that of inner columns of crinoid stems (single crystal), in which the rhombohedral cleavage can be clearly observed . Therefore, it can be supposed that the free swimming or floating larvae, once they met some cylindrical objects (mostly crinoid stems) could settle on them. Afterwards the mantle began secreting the calcareous shell , forming the attachment ring and the

PLATE 2 Fig. 1-11, 14 - Laterispina parallela, nov. sp. 1, a cross section of a trapezoidal central platform x 50, CHNT9030, showing the irregular septa wihtin the central platform and the median septum on the central platform and the pseudopunctatae in the lower part of the central platform. 2, cross section of a complete specimen x 5, CHNT9030, showing the central platform and the concavo-convex cavity. 3, cross section of a central platform without internal septum x 30, CHNT9101, showing the med ian septum and the pseudopunctate layer, and the laminar fabric layer. 4, x 17, CHNT9101, the strong brachiophore process on the dorsal valve. 5, x 14, CNHT9101, the pseudopuncate layer and the laminar layer. 6, cross section of a compl ete specimen x 4.5 , CHNT9101, showing the strong brachiophore process in the dorsal valve, the central platform and the thickened median septum. 7, cross section x 4.5, CHNT9029, showing the central platform and the two layers of both valves. 8, the central platform x 16,CHNT9029. 9 , x 40, CHNT9029, the internal septa in the central platform. 10, x 20, CHNT9029, the two layers of both valves. 11, x 250, CHNT9101 , pseudopunctatae. 14, section of the posterior part x 4, CHNT9031, showing the attachment rig and the crinoid stem. 12·13, living terebratulids ; 12, longitudinal section of the punctatae, x 100 ; 13 tranverse section of the punctatae, x 200 , CHNT9028. 1, coup e transversale d'une plate-forme centrale trapezoidale montrant les septes irreguliers, le septum median sur la plate-forme et les pseudopunctuations dans la partie inferieure de la plate-forme. 2, section transversale d'un specimen complet montrant la plate-forme centrale et la cauite concavo-con vexe. 3, section transversale d'une plate-forme centrale sans septum interne, montrant le septum median, la couche pseudoponctuee et la couche lamellaire. 4, ph oto du fort processus du brachiophore de la valv e dorsal e. 5, couche pseudoponctuee et couche lamellaire. 6, section transversale d'un specimen compl et montrant le processus du brachiophore, a la valve dorsale, la plate-forme centrale et le septum median epaissi. 7, section transversal e montrant la plate-forme centrale et les deux couches de chaque valve. 8, plate-forme centrale. 9, les septes internes dans la plate-forme centrale. 10, les deux couches des deux valves. 11, pseudoponctuations. 12-13, terebratulide actuel : 12, coupe longitudinale des ponctuations ,. 13, coupe transversale.

PI. 2 S. Shen, B. Fan, C. Zhang & X. Zhang

Geobios n° 27, fase. 4

,.

484 advanced function as a prop. By of that me ans the permianellids could not only freel y rotate around the crinoid stems, but also move upward and downward along the crinoid stems according to changes in the environment. However, the cross sect ion (PI. 2, fig. 14) reveals that the permianellids did not have this adv anced function because the attached portion of the crinoid stems is usually more slender than t he adjacent portions. The permianellids, often as sociated with a great number of benthic organisms including bryozoans, bivalves, corals and fusulinids etc. , generally are found in thin - bedd ed mudstones or limestones. The associated brachiopods usually have a high diversity and are preserved in abnormal living states. Sh ell fragments are often seen and all crinoids are preserved as detached ste ms. POPULATION STRUCTURE

Figure 3 • Paleoecologic reconstruction of L. parallela. Reconstitution du mode de vie.

elongated extended valves, possibly indicating that they grew in declined or pendant directions. The different attachment states probably determined the variable morphology of this species, including symmetry and asymmetry which were considered as the characters of the superfamily by Liang (1990). At the 3rd Chinese Brachiopod Conference in 1990 , Liang thought that permianellids had an

Th e Laterispina parallela population is a local breeding one. Determining the age of shell is difficult within a population. Th e a uthors use the length of permianellids to indicat e their age . Examination of 87 specimens produces the size frequency distribution histogram of Figure 4, and the surv ivorshi p curve of Figure 5. The size freque ncy distribut ion is typically bell and the s urvivorship curve is negatively skewed, showing sh aped the population increas ing mortality with age. Fagerstorm (1964) considered th at if large are as of the sea floor were swept by relatively weak currents of low competence, th e small empty shells of uncemented benthic and pelagic sp ecies would be removed by currents in th ese areas . Th e residue consists mostly of large sh ells wh ich, upon burial, become residual fossil communities . The effect of this selective removal of large num-

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485 A.J. Boucot and Dr. M. Pickford, Dr. P.R Racheboeuf and Prof. K. Nakamura for carefully checking the English manuscript.

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REFERENCES

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COOPER G.A. & GRANT RE. 1969 - New Permian brachiopods of West Texas. Smithsonian contributions to Paleobiology, 1 : 1-20. COOPER G.A & GRANT RE. 1974 - Permian brachiopods of West Texas, II. Smithsonian contributions to Paleobiology, 15 : 384-450. GRANT RE. 1972 - The lophophore and feeding mechanism of the Productidina. Journal of Paleontology, 46, 2: 213-249. GRANT RE. 1976 - Permian brachiopods from Southern Thailand. Journal of Paleontology, 50, supplement to 3, 9 : 160-173. HE X.L & ZHU M.L. 1979 - A new form of brachiopods and its systematical classification. Journal of China Institute of Mining and Technology, 4 : 131-140. LIANG W.P. 1982 - Brachiopoda. In : Palaeontological atlas in East China (in Chinese). Geological Pu-

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bers of small, empty shells is to change right-skewed size frequency distribution of unwinnowed populations to distributions that are bell-shaped or normal. The L. parallela population should have a higher juvenile mortality. It depended on whether they could find a suitable host that could bear the weight of their shells. According to the preserved states of fossils, the paleoenvironment at that time was undoubtedly influenced by waves or currents. Thus the small and thin shells were transported easily. We think that the size frequency curve of the L. parallela population was altered by currents or waves. All above analyses show that the individuals of this population belong to higher epizoan feeders in the soft substrate community near normal wave base.

Acknowledgements - The authors would like to express their gratitude to Dr. Richard E. Grant of the Smithsonian Institution, who kindly provided critical opinions on the classification of the permianellids, and to Prof. He Xilin for his important supervision of some aspects of permianellids. The authors also thank Prof.

LIANG W.P. 1990 - Lengwu Formation of Permian and its brachiopod fauna in Chekiang Province (in chinese with English summary). People's Republic of China Ministry of Geology and Mineral Resources. Geological Publishing House, Beijing, 2, 10. Mu C.J. & Lnr C.L. 1989 - Guangdongina and its ecological environment (in Chinese). Acta palaeoniologica Sinica, 28, 4 : 460-470. STEHLI F.G. 1954 - Lower Leonardian Brachiopoda of the Sierra Diablo. American Museum of Natural History Bulletin, 105, 3 : 263-358. TERMIER H. et al. 1974 - Monographie du Permo-Carbonifere de Wardak (Afghanistan Central). Documents des Laboratoires de Geologie de la Faculte des Sciences de Lyon, 2. WANG H.Y. & CHING Y.G. 1991 - On Permianellids (Brachiopoda). Acta Palaeontologica Sinica, 30, 4 :

481-501. WANNER J. & SIEVERTS H. 1935 - Zur Kenntnis der Permischen Brachiopoden von Timor, 1 : Lyttoniidae und ihre Biologischen und Stammes-geschichtliche Bedeutung. Neues Jahrbuch [iir MineraLogie, Geologie und Paliiontologie, 74, B : 201-281. WILLIAMS A. 1953 - The morphology and classification of the oldhaminid brachiopods. Washington Academy of Sciences Journal, 43, 9 : 279-287. YANG D.L. 1984 - Brachiopoda. In : Biostratigraphy of the Yangtze Gorge area (in Chinese). Geological Publishing House, Beijing. SHEN S. & FAN B. Department of Geology China University of Mining & Technology Xuzhou City Jiangsu Province 221008, China ZHANG C. & ZHANG X. Winjiang Archaeology Institute Urumchi City, Xinjiang Uygur Autonomous Region, 830011 China