ISSN 00310301, Paleontological Journal, 2013, Vol. 47, No. 4, pp. 363–365. © Pleiades Publishing, Ltd., 2013. Original Russian Text © A.S. Biakov, 2013, published in Paleontologicheskii Zhurnal, 2013, No. 4, pp. 16–19.
New Permian Pteronites (Bivalvia, Pinnidae) from the Lower Permian of the Omolon Massif, Northeastern Asia A. S. Biakov Shilo Northeast Interdisciplinary Scientific Research Institute, Far East Branch, Russian Academy of Sciences, Portovaya ul. 16, Magadan, 685000 Russia email:
[email protected] Received October 22, 2012
Abstract—Distribution of members of the thermophilic genus Pteronites in the Upper Paleozoic beds of northeastern Asia is briefly considered. A new species, Pteronites magnus sp. nov., from the Lower Permian of the Omolon Massif is described. Keywords: Bivalvia, Pinnidae, new taxa, Lower Permian, Omolon Massif, Russian, Asia DOI: 10.1134/S0031030113040060
INTRODUCTION Until recently, bivalves were believed to play a minor role in benthic communities of the Early Per mian (Asselian–Artinskian) seas of northeastern Asia. During the last decade, new extensive paleontological material from a number of sections of the Omolon Massif provided a better understanding of this faunal group. The knowledge of the taxonomic composition of Lower Permian communities and their stratigraphic distribution essentially expanded. Some results have been published (Biakov, 2005, 2009, 2010, 2011). In contrast to brachiopods, Asselian–Artinskian communities of which include a significant proportion of endemic taxa (Ganelin, 1984), the bivalve fauna has much in common with contemporaneous communi ties of western Australia (Dickins, 1963) and is domi nated by the genera Schizodus, Solemya, Oriocras satella, Pyramus, Myophossa, Cosmomya, Wilkingia, Palaeocosmomya, Vacunella, Astartella, and Cypricar dinia. Many of these genera show bipolar distribution. The presence of some thermophilic genera, such as Myalina and Pteronites is rather indicative; in the Per mian, they are only known from lowlatitude basins of the Boreal Superrealm (Volga–Ural and West Euro pean basins) and the Tethys (North America). Members of the genus Pteronites are rather rare in the Upper Paleozoic of northeastern Asia. Almost all of them are known from sections of the Omolon Mas sif and its southeastern surroundings (Gizhiga Folded Zone). From the Middle Carboniferous (Olcha For mation), Muromtseva (1974) described the species P. muticus (MacCoy) and, from the middle part of the Magiveem Formation (presumably Verchojania expositus Brachiopod Zone, Orochian Horizon of the Lower Permian), an extraordinary representative of this genus, P.? costatus (Muromzeva), with a rough
concentric ornamentation atypical for the genus, which probably deserves generic rank. Members of Pteronites in our collection, except for the species considered in the present study, are also determined from the Olcha Formation of the Middle Carboniferous and the lower part of the Koargy chanian Horizon of the Lower Permian (Edmondia gigantea Bivalve Zone, middle part of the Artinskian Stage). These are unusual singular forms determined only to genus in open nomenclature. In younger Per mian bivalve assemblages of northeastern Asia, Ptero nites has not been recorded. The present study describes a new species of the genus Pteronites from the Asselian beds of the Omolon Massif (Euchondria? mira Bivalve Zone). The material was collected by N.I. Karavaeva (Central Complex Thematic Expedition of the Production Geological Association “Sevvostgeologiya”) on the right bank of the Omolon River (Ledyanaya River). Remains of Pteronites come from sandy limestones of the lower part of the Nam Formation along with the brachiopods Verchojania expositus (Ganelin), Costatumulus ex gr. grandis (Solomina), and Anidanthus ex gr. bojkovi (Stepanov) (identified by V.G. Ganelin) and the bivalves Solemya cf. holmwoodensis Dickins, “Aviculopecten” fre derixi Lutkevich et Lobanova, Vacunella praecurvata AstafievaUrbajtis, Grammysiopsis omolonicus Muromzeva, Myophossa subarbitrata (Dickins), etc. The geographical position of the section which has yielded the material described here is shown in Fig. 1. A very important point is the fact that a complete specimen of the new species was found in the collec tion stored in the Geological Museum of the Stuken berg Kazan (Volga Region) State University, Kazan (KGU), which probably comes from the same locality as Karavaeva’s specimens. The following abbreviations are used in the description: (H) shell height, (Vc) valve convexity,
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BIAKOV 168° E
Bolshoi An yui River
Srednekolymsk
156°
Circle
Arctic
Olo i
od Kork
r ve Ri
er Riv
n olo Om
a lym Ko n ska Ta
iver on R
64° N er Riv
Gi zh iga
Inya Riv er
Penzhina River
Pa ren ’R
Ri ve r
ive r
r Rive cha hap Bak
r ve Ri ma y l Ko
Che lomd zhaR iver
Riv er
Magadan
100 km
Sea of Okhotsk
Fig. 1. Locality of the new species of the genus Pteronites (designated by a black circle) in northeastern Asia.
(MD) length of the main shell diagonal, (L) shell length, (LHL) hinge line length, (AA) apical angle, and (OA) valve obliquity angle. Most of the material investigated is stored in the Museum of the Shilo Northeast Interdisciplinary Sci entific Research Institute of the Far East Branch of the Russian Academy of Sciences (SVKNII), Magadan, collection no. 0206.98, and the holotype is housed in the Geological Museum of Stukenberg Kazan (Volga Region) State University (KGU), collection no. 14639. SYSTEMATIC PALEONTOLOGY Family Pinnidae Leach, 1819 Genus Pteronites MacCoy in Griffith, 1844 Pteronites magnus Biakov, sp. nov.
E t y m o l o g y. From the Latin magnus (large).
H o l o t y p e. KGU, no. 39/14639, mold of a two valve specimen with fragmentarily preserved shell; Omolon Massif, Ledyanaya River, left bank of the Bol’shaya Avlondya River, right tributary of the Omo lon River; Lower Permian, Asselian Stage, Orochian Horizon, Euchondria? mira Bivalve Zone, lower part of the Nam Formation. D e s c r i p t i o n (Figs. 2a, 2b). The shell is very large, MD is about 200 mm, extended triangular (L : H = 2.71), wedgeshaped, strongly oblique (OA = 15°–18°), expanding evenly posteroinferiorly, and rel atively thickwalled. The cross section of the shell is rhomboid, with convex sides. The hinge line is very long, much more than half as long as the shell (LHL : L = 0.72), connected to the anterior margin, forming an abrupt arch of small radius. The anterior margin is very short, abruptly passes into a very long, almost straight or slightly con vex lower margin. The last passes abruptly into a rela tively short, slightly rounded (judging from growth lines) posterior margin, which is connected to the hinge margin at a blunt angle about 110°. The shell is moderately convex (Vc : H = 0.19), the point of the greatest convexity is in the middle part of the valve and approximately equidistant from the hinge and lower margins. The beaks are subterminal, very small, not overhanging, poorly discernible, smoothed. The anterior ear is small, poorly differenti ated. The anteroinferior field adjoining it is somewhat flattened. Judging from the molds, the shell surface was almost smooth; the posterior field has weak, relatively uniform growth lines. They begin close to the hinge line and extend posteroinferiorly at a blunt angle about 100°; then, at a distance from the lower margin, they abruptly curve and pass anteriorly almost in parallel to it. The scar of the posterior muscle is distinct, large, rounded oval, up to 25 mm high, located in the poste rior onethird of the valve and shifted towards the hinge line. The scar of the anterior muscle is small, about 3 mm long, round, located in the anterior field of the shell close to the lower margin. The prismatic layer is up to 1.5 mm thick, a thin nacreous layer is also present.
M e a s u r e m e n t s i n m m a n d r a t i o s: Specimen Holotype KGU, no. 39/14639 SVKNII, no. 202/0206.99
L
H
Vc
MD
LHL
OA
AA
L:H
Vc : H
LHL : L
ca.190
70
13
ca. 200
136
18°
25°
2.71
0.19
0.72
>75
ca. 54
ca. 7*
–
–
15°
22°
–
ca. 0.13*
–
Note: (*) with some distortion.
C o m p a r i s o n. The new species differs from all known congeners in the large size and the shell expanding considerably posteroinferiorly. In particu
lar, it differs from P. timanicus (Maslennikow) from the Middle Permian of southern Timan (Maslenni kow, 1935) in the somewhat larger and much more PALEONTOLOGICAL JOURNAL
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(a)
(b) Fig. 2. Pteronites magnus sp. nov., ×1: (a) holotype KGU, no. 39/14639, right valve view; (b) specimen SVKNII, no. 202/0206.99, left valve view.
posteroinferiorly expanded shell (in P. timanicus, L : H is more than 4) and in the larger (by 4°–7°) apical angle. It differs from the specimen determined by Muromtseva as P. muticus (MacCoy) from the Middle Carboniferous (Khayam Formation) of the southeast ern marginal area of the Omolon Massif (Gizhiga Folded Zone) in the more posteroinferiorly widened shell (in this specimen of P. muticus, L : H is about 3.4) and in the more regular character of the growth lines. O c c u r r e n c e. In addition to the type region, it probably occurs in the Lower Permian (Khorokytskian Horizon) of the southern Verkhoyansk Region, where from a representative of the new species (collected by A.G. Klets) is recorded. M a t e r i a l. Two molds with fragmentarily pre served shell (one of them is the posterior part), a mold fragment of the left valve, and two fragments of shell imprints from one locality. ACKNOWLEDGMENTS I am sincerely grateful to the director of the Geo logical Museum V.V. Silant’ev and the former major keeper S.V. Kurkova for great help in my work with the bivalve collection housed in Kazan. This study was supported by the Russian Founda tion for Basic Research, project nos. 110500053 and 110500950.
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REFERENCES Biakov, A.S., New species of astartids and pholadomyids (Bivalvia) and beds with fauna from the Lower Permian of the Omolon Massif, Northeastern Asia, Paleontol. Zh., 2005, no. 2, pp. 30–37. Biakov, A.S., New zonal bivalve species from the Permian of northeastern Asia, Vestn. Sev.Vost. Nauchn. Tsentra Dal’nevost. Otd. Ross. Akad. Nauk, 2009, no. 4, pp. 23–26. Biakov, A.S., Zonal’naya stratigrafiya, sobytiinaya korre lyatsiya, paleobiogeografiya permi SeveroVostoka Azii (po dvustvorchatym mollyuskam) (Zonal stratigraphy, event correlation, and paleobiogeography of the Permian of northeastern Asia, based on bivalves), Magadan: Sev.Vost. Kompl. NauchnoIssled. Inst. Dal’nevost. Otd. Ross. Akad. Nauk, 2010. Biakov, A.S., New species of Inoceramuslike bivalves of the genus Aphanaia Koninck from the Lower Permian of north east Asia, Paleontol. Zh., 2011, no. 1, pp. 7–13. Dickins, J.M., Permian pelecypods and gastropods from western Australia, Bull. Bur. Miner. Res. Geol. Geophys. Aus tralia, 1963, no. 63, pp. 1–203. Ganelin, V.G., Taimyr–Kolyma Subregion, Tr. Vsesoyuz. Geol. Inst. Nov, Ser., 1984, vol. 286 (Main stratigraphic fea tures of the Permian System of the USSR), pp. 111–142. Maslennikow, D.F., Upper Permian lamellibranchiates of the Northern Region, Tr. Tsentr. NauchnoIssled. Geol. Razved. Inst., 1935, vol. 29, pp. 1–124. Muromtseva, V.A., Bivalves from the Carboniferous of Kazakhstan and Siberia, Tr. Vses. NauchnoIssled. Geol. Razved. Inst., 1974, no. 336, pp. 1–150.
Translated by G. Rautian
