ISSN 00310301, Paleontological Journal, 2015, Vol. 49, No. 5, pp. 464–473. © Pleiades Publishing, Ltd., 2015. Original Russian Text © V.V. Baranov, 2015, published in Paleontologicheskii Zhurnal, 2015, No. 5, pp. 16–23.
New Atrypids (Brachiopoda) from the Emsian (Lower Devonian) of Northeast Eurasia V. V. Baranov Diamond and Precious Metal Geology Institute, Siberian Branch, Russian Academy of Sciences, pr. Lenina 39, Yakutsk, 677007 Russia email:
[email protected] Received April 9, 2014
Abstract—New atrypid taxa (Brachiopoda) are described from the Emsian Stage, Lower Devonian of north eastern Eurasia: Copperella gen. nov. with its type species C. kaskevichi sp. nov. (subfamily Spinatrypinae Cop per); Ogilviella gerensis sp. nov., Raisiya gen. nov. with its type species R. solonchanensis sp. nov. (subfamily Atrypininae McEwan); Misensia gen. nov. with its type species M. gracilis sp. nov. (subfamily Atrypinellinae Copper); and Bifida rara sp. nov. (subfamily Anoplothecinae Schuchert). Keywords: Atrypids, brachiopods, Lower Devonian, Emsian, Northeast Eurasia DOI: 10.1134/S0031030115050044
INTRODUCTION All of the previously described taxa of Emsian atrypids from northeastern Eurasia were based on specimens obtained by the mechanical preparation. I identified new atrypid taxa described here after the dissolution of carbonate rock samples from different stratigraphic levels of the Emsian Stage of northeast ern Eurasia in acetic acid. Although spinatrypin and keeled atrypoid brachiopods are very widespread in the Emsian deposits of northeastern Eurasia, they are very poorly known. The most complete summary on the systematic composition of Emsian atrypids is presented in the collective paper of Alekseeva et al. (1996). I found very small shells of atrypids Copper ella gen. nov. with fine spines on the growth lamellae in the Geremgandzha Formation of the TasKhaya khtakh Range. The following atrypids have carinate shell shape: Ogilviella Lenz, 1968, Raisiya gen. nov. (subfamily Atrypininae) and Bifida Davidson (sub family Anoplothecinae). The type species of Ogil viella, O. gerensis sp. nov., was found in the Emsian deposits of the Chersky Mountain System (Tas Khayakhtakh Mountain Ridge). A. Lenz (1968) was the first to describe Ogilviella (O. rotunda Lenz) from the presumably Siegenian (Pragian) deposits of northern Yukon (Canada). Later N. Savage (1970) described Ogilviella prolifica from the Siegenian deposits of Australia (New South Wales). Although both researchers placed Ogilviella in the subfamily Carinatininae Rzhonsnitskaya, 1960, P. Copper (2002) tentatively included it into the subfamily
Spirigerininae Rzhonsnitskaya. In my opinion Ogil viella should be assigned to Atrypininae McEwan since it has all diagnostic features of this subfamily. I also described representatives of a new genus, Raisiya (R. solonchanensis sp. nov.), as belonging to Atrypininae and a new genus, Misensia, as belonging to the subfamily Atrypinellinae. In his diagnosis of Bifida, P. Copper (2002) mentioned the presence of dense spinose fibers on the concentric growth lamel lae and small cardinal process. I also obtained addi tional data on the shell exterior and interior of the species of this genus. Thus a new species, B. rara, have fine spines on the margins of growth lamellae. The dorsal valve of this species contains a massive hinge plate and high inner socket ridges and lacks cardinal process. No cardinal processes were found in B. ogilviensis (Perry et al., 1974, p. 1076, textfigs. 19, 21) and in the cross sections through the shell of the type species of Bifida, B. lepida (Copper, 2002, p. 1608, textfigs. 1j–1o). The geographic and stratigraphic allocations of samples are presented in the monograph of T.S. Alkhovik and V.V. Baranov (2001) and in Figs. 1 and 2. The photographs were produced by the employer of the Laboratory of Stratigraphy and Pale ontology of GM DPMGI A.G. Stepanov. The brachiopod collection is stored in the Geolog ical Museum at the Diamond and Precious Metal Geology Institute (GM DPMGI), Yakutsk with coll. no. 217.
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Fig. 1. Schematic map of the Lower and Middle Devonian outcrops with the finds of atrypids in northeastern Eurasia. Designa tions: (1)–(5) sections: (1) Khobochalo2, (2) GeremgandzhaGer, (3) DatnaII2, (4) Gon1, (5) Tebetei, (6) Izvestkovyi Kar’erII.
SYSTEMATIC PALEONTOLOGY
S p e c i e s c o m p o s i t i o n. Type species. C o m p a r i s o n. Copperella gen. nov. differs from Spinatrypa Stainbrook, 1951 in the smaller shell, more convex ventral valve, flat apsacline area and fine spines on the growth lamellae. The new genus differs from Oglu Havlicek, 1987 and Invertrypa Struve, 1961 in the presence of fine spines on the growth lamellae.
Order Atrypida Suborder Atrypidina S u p e r f a m i l y Atrypoidea Gill, 1871
ˆ
Family Atrypidae Gill, 1871 Subfamily Spinatrypinae Copper, 1978
Copperella kaskevichi Baranov, sp. nov.
Genus Copperella Baranov, gen. nov.
Plate 3, figs. 1, 2
E t y m o l o g y. In honor of the famous Canadian paleontologist P. Copper. Ty p e s p e c i e s. Copperella kaskevichi sp. nov. D i a g n o s i s. Shell very small, oval, coarsely ribbed, biconvex, with more convex ventral valve. Area flat and apsacline; delthyrium covered by deltidial plate; foramen rounded and permesothyridid. Valve surface covered with coarse ribs, which cross wide concentric growth lamellae. Surface of growth lamel lae bears fine spines. In ventral valve, dental plates absent. Dorsal valve interior unknown. PALEONTOLOGICAL JOURNAL
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E t y m o l o g y. In honor of the geologist G.E. Kaskevich. H o l o t y p e. GM DPMGI, no. 217/1, complete shell; Northeastern Eurasia, eastern slope of the Tas Khayakhtakh Range, right bank of the Krivoi Ruchei Creek (right tributary of the Tebetei River); Emsian Stage, Nikolaevka regional stage, excavatus Zone. Description. The shell is very small, oval, biconvex, with maximum width in the middle and maximum thick ness in the posterior half of the valves. The cardinal extremities are rounded. The anterior commissure is
BARANOV 2. GeremgandzhaGer section
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intraplicate. The ventral valve is slightly convex, with maximum thickness in the posterior half of the valves. The beak is straight and projecting. The area is flat and apsacline. The delthyrium is covered by deltidial plate.
The foramen is small, rounded, and permesothyridid. The dorsal valve is convex, with maximum thickness in its posterior half. The ornamentation consists of six–eight coarse ribs, which start from the umbo, widen towards
Explanation of Plate 3 Figs. 1 and 2. Copperella kaskevichi sp. nov.: (1) holotype GM DPMGI, no. 217/1, ×6.3: (1a) ventral valve; (1b) dorsal valve; (1c) lateral view; (1d) anterior view; (1e) microornamentation, ×12.5; Chersky Mountain System, eastern slope of the TasKhay akhtakh Range, downstream of Krivoi Ruchei Creek (right tributary of the Tebetei River); Lower Devonian, Emsian Stage, Ger emgandzha regional stage, Geremgandzha Formation; (2) specimen GM DPMGI, no. 217/2, ×6: (2a) ventral valve; (2b) ventral valve interior; (2c) microornamentation, ×15; Chersky Mountain System, TasKhayakhtakh Mountain Ridge, left bank of the DatnaII River, DatnaII2 section; Lower Devonian, Emsian Stage, Geremgandzha regional stage, Geremgandzha Formation. Figs. 3–9. Ogilviella gerensis sp. nov.: (3) holotype GM DPMGI, no. 217/10, ×6: (3a) ventral valve; (3b) dorsal valve; (3c) lateral view; (3d) anterior view; Yukaghir Plateau, right bank of the Kolyma River, Izvestkovyi Kar’erII section; Lower Devonian, Emsian Stage, Nikolaevka regional stage, Izvestkovyi Kar’er Formation; (4) specimen GM DPMGI, no. 217/11, ×5.7: (4a) ven tral valve; (4b) dorsal valve; (4c) lateral view; (4d) anterior view; Chersky Mountain System, TasKhayakhtakh Range, right bank of Ger Creek, GeremgandzhaGer section; Lower Devonian, Emsian Stage, Geremgandzha regional stage, Geremgandzha For mation; (5) specimen GM DPMGI, no. 217/12, ×6: (5a) ventral valve; (5b) dorsal valve: (5c) lateral view; (5d) anterior view; (6) specimen GM DPMGI, no. 217/13, ×9.6: (6a) ventral valve; (6b) dorsal valve; (6c) lateral view; (6d) anterior view; (7) spec imen GM DPMGI, no. 217/14, ×9: (7a) ventral valve; (7b) dorsal valve; (7c) lateral view; (7d) anterior view; (8) specimen GM DPMGI, no. 217/15, ×12: (8a) ventral valve; (8b) dorsal valve; (8c) lateral view; (8d) anterior view; (9) specimen GM DPMGI, no. 217/16, ventral valve interior, ×20; TasKhayakhtakh Mountain Ridge, left bank of the DatnaII River, DatnaII2 section; Lower Devonian, Emsian Stage, Geremgandzha regional stage, Geremgandzha Formation. PALEONTOLOGICAL JOURNAL
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467 Plate 3
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the anterior margin, and are crossed by wide concentric growth lamellae bearing fine spines. S h e l l i n t e r i o r (Pl. 3, fig. 2b). In the ventral valve, the dental plates are absent. Dorsal valve interior is unknown. D i m e n s i o n s i n m m a n d r a t i o s: Specimen GM sample, DPMGI, no. no.
L
W
T
L/W
L/T
Holotype 217/1 5161/4
5.6
8.0
3.0
0.7
1.9
M a t e r i a l. Four satisfactorily preserved shells from two localities: one specimen from the Chersky Mountain System, eastern slope of the TasKhaya khtakh Range, right bank of the Krivoi Ruchei Creek (right tributary of the Tebetei River), sample T5161/4; left bank of the Datna II2 River, DatnaII2 section: two specimens from the sample T64/4 and one speci men from sample T64/7. Subfamily Atrypininae McEwan, 1939 Genus Ogilviella Lenz, 1968 Ogilviella gerensis Baranov, sp. nov. Plate 3, figs. 3–9
E t y m o l o g y. From Ger Creek, left tributary of the Geremgandzha River. H o l o t y p e. GM DPMGI, no. 217/10, complete shell; northeastern Eurasia, Yukaghir Plateau, right bank of the Kolyma River; Limestone quarryII sec tion; Lower Devonian, Emsian Stage, Nikolaevka regional stage, excavatus Zone, Izvestkovyi Kar’er Formation. D e s c r i p t i o n. The shell is very small, oval, biconvex, with maximum width and thickness in the middle. The cardinal extremities are rounded. The anterior commissure is intraplicate. The ornamenta tion consists of coarse ribs, which are crossed by nar row concentric lamellae and growth lines. The ventral valve is slightly convex, with maximum thickness in the middle. The umbo is straight and projecting. The deltidial plate closes the delthyrium. Two rounded ribs start from the umbo, form an elevation, and dichoto mize towards the anterior margin forming a bundle. Each lateral valve surface bears six to eight rounded, simple ribs. The dorsal valve is convex, with maximum thickness in the middle. The sulcusshaped depression starts from the umbo and widens towards the anterior margin. The median rib runs along its bottom from the umbo; two additional ribs may arise by intercalation laterally of the median rib. Lateral ribs border the sul cusshaped depression and dichotomize near the anterior margin. Each lateral surface of the dorsal valve bears six to ten ribs. S h e l l i n t e r i o r. In the ventral valve, the dental plates are absent. The dorsal valve interior is unknown.
D i m e n s i o n s i n m m a n d r a t i o s: Specimen GM DPMGI, no.
sample, no.
L
W
T
L/W
L/T
Holotype 217/10
К7/1
4.3
4.3
2.1
1.0
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217/11 Т49/1
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4.2
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1.5
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2.4
1.7
1.2
1.6
217/15 Т64/4
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2.0
1.0
1.0
2.0
C o m p a r i s o n. The new species differs from O. rotunda (Lenz, 1968, p. 181, pl. 31, figs. 1–35), O. prolifica (Savage, 1970, p. 657, pl. 101, figs. 1–33), and O. ? sp. (Chatterton and Perry, 1974, p. 35, text figs. 16–20) in the very small shell, smaller number of lateral ribs and absence of their dichotomy. O c c u r r e n c e. Lower Devonian, Emsian Stage, Nikolaevka and Geremgandzha regional stages, exca vatus–inversus conodont zones, Izvestkovyi Kar’er Formation of the Yukaghir Plateau (right bank of the Kolyma River) and Geremgandzha Formation of the TasKhayakhtakh Range. M a t e r i a l. Fifteen satisfactorily preserved shells from three localities: one specimen from the Yukaghir Plateau, right bank of the Kolyma River, Limestone quarryII section, sample K7/1; two specimens from the Chersky Mountain System, TasKhayakhtakh Mountain Ridge, right bank of Ger Creek, left tribu tary of the Geremgandzha River, sample T49/1; left bank of the Datna II–2 River, Datna II2 section: six specimens from the sample T64/4 and three speci mens from the sample T64/5; and three specimens from the right bank of Krivoi Ruchei Creek, right trib utary of the Tebetei River, sample T5161/4. Genus Raisiya Baranov, gen. nov.
E t y m o l o g y. In honor of the famous Russian paleontologist Raisa Evgrafovna Alekseeva. Ty p e s p e c i e s. R. solonchanensis sp. nov. D i a g n o s i s. Shell very small, oval, and coarsely ribbed. Anterior commissure sulciplicate. Ventral valve from slightly to moderately convex. Area apsacline; delthyrium covered by deltidial plate; foramen very small and permesothyridid. Median rib dichotomizes towards anterior margin. Dorsal valve may be flattened or slightly convex and bears median depression with median rib developed in its anterior half. Each lateral valve surface bears four simple rounded ribs and two poorly developed, which are crossed by narrow con centric growth lamellae. Dorsal valve with massive PALEONTOLOGICAL JOURNAL
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subhorizontal hinge plates; middle area of inner valve surface elevated. S p e c i e s c o m p o s i t i o n. Type species. C o m p a r i s o n. The new genus differs from Atryp ina Hall et Clarke, 1893, Ogilviella Lenz, 1968 and sub genus Gracianella (Sublepida) Mizens et Sapelnikov, 1982 in the dichotomizing median rib on the ventral valve and absence of dichotomy and intercalation in lat eral ribs. Raisiya also differs from Ogilviella in the intra plicate anterior commissure and elevated middle area of the inner surface of the ventral valve. Raisiya solonchanensis Baranov, sp. nov. Plate 4, figs. 1–5
E t y m o l o g y. From the Solonchan River, right tributary of the Dogdo River. H o l o t y p e. GM DPMGI, no. 217/20, complete shell; northeastern Eurasia, Chersky Mountain Sys tem, TasKhayakhtakh Range, Ger Creek, left tribu tary of the Geremgandzha River; GeremgandzhaGer section; Lower Devonian, Emsian Stage, Nikolaevka regional stage, excavatus zone, Upper Khobochalo Subformation. D e s c r i p t i o n. The shell is very small, oval, biconvex, with maximum width and thickness in the middle. The cardinal extremities are rounded. The anterior commissure is intraplicate. The ornamenta tion consists of gentle folds, which are crossed by nar row concentric lamellae. The ventral valve is convex, with maximum thickness in the middle. The umbo is slightly curved or straight. The delthyrium is closed by deltidial plate with permesothyridid foramen at the apex. Two rounded ribs start from the umbo, form keelshaped elevation and dichotomize at a short dis tance from the umbo. Each valve area laterally of the elevation bears two rounded and two poorly developed folds. The dorsal valve is slightly convex, with maxi mum thickness in the middle. The sulcusshaped depression starts from the umbo and widens towards the anterior margin. One median rib runs along its bottom from the umbo. The dorsal valve also bears two ribs bordering the sulcusshaped depression and two additional ribs. S h e l l i n t e r i o r. In the ventral valve, the dental plates are absent. Middle area of the inner valve sur face is elevated. The dorsal valve interior is unknown. D i m e n s i o n s i n m m a n d r a t i o s: Specimen GM DPMGI, no.
sample, no.
L
W
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L/W
L/T
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~4.0
3.0
1.0
1.2
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M a t e r i a l. Sixteen satisfactorily preserved shells: one specimen from the Yukaghir Plateau, right bank of the Kolyma River, Limestone quarryII section, sam ple K7/1; two specimens from the Chersky Mountain System, TasKhayakhtakh Range, right bank of Ger Creek (left tributary of the Geremgandzha River), sample T49/1; six specimens from left bank of the Datna II2 River, Datna II2 section, sample T64/4; and seven specimens from left bank of the Khobochalo River, Khobochalo2 section, sample T18/5. S u p e r f a m i l y Punctatrypoidea Rzhonsnitskaya, 1960 Family Punctatrypidae Rzhonsnitskaya, 1960 Subfamily Atrypinellinae Copper, 2002 Genus Misensia Baranov, gen. nov.
E t y m o l o g y. In honor of the famous Russian paleontologist L.I. Mizens. Ty p e s p e c i e s. M. gracilis sp. nov. D i a g n o s i s. Shell very small, strongly carinate, elongated, flattened, biconvex; ventral valve more convex and bears keel; dorsal valve with sulcusshaped depression. Umbo straight; foramen oval and perme sothyridid; delthyrium closed by deltidial plate. Valve surfaces covered with thin ribs, which are crossed by concentric lamellae and growth lines. In ventral valve, dental plates absent. Dorsal valve interior unknown. S p e c i e s c o m p o s i t i o n. Type species. C o m p a r i s o n. The new genus differs from Atrypinella Khodalevich, 1939 in the small, elongated, flattened, strongly carinate shell, concentric lamellae and growth lines and presence of deltidial plate. It dif fers from Limbatrypa Copper, 1982 and Reticulatrypa Savage, 1970 in the small, elongated, flattened, and strongly carinate shell and coarse ribs. Misensia gracilis Baranov, sp. nov.
E t y m o l o g y. From the latin gracilis (graceful). H o l o t y p e. GM DPMGI, no. 217/40, complete shell; northeastern Eurasia, Chersky Mountain System, TasKhayakhtakh Range, DatnaII River (right tribu tary of the Dogdo River), DatnaII2 section; Lower Devonian, Emsian Stage, Geremgandzha regional stage, inversus Zone, Geremgandzha Formation. D e s c r i p t i o n (Fig. 3). The shell is very small, oval, and biconvex, with maximum width and thick ness in the middle. The cardinal extremities are rounded. The ornamentation consists of thin, rounded, dichotomizing and intercalating ribs, which are crossed by concentric lamellae and growth lines. The ventral valve is slightly convex, with maximum thickness in the middle. The umbo is straight. The delthyrium is closed by deltidial plate pierced with permesothyridid foramen. Four rounded ribs start from the umbo, form keel or elevation, and strongly dichotomize towards the anterior margin. The eleva
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Fig. 3. Misensia gracilis gen. et sp. nov.: (a)–(d) holotype no. 217/40, ×4.3: (a) ventral valve; (b) dorsal valve; (c) lateral view; (d) anterior view; (e)–(g) specimen GM DPMGI, no. 217/41, ×4.3: (e) ventral valve; (f) dorsal valve; (g) lateral view; (h)⎯(k) specimen GM DPMGI, no. 217/42, ×5.3: (h) ventral valve; (i) dorsal valve; (j) lateral view; (k) anterior view; (l)–(o) spec imen GM DPMGI, no. 217/43, ×5: (l) ventral valve; (m) dorsal valve; (n) lateral view; (o) anterior view; (p)–(s) specimen GM DPMGI, no. 217/44, ×5: (p) ventral valve; (q) dorsal valve; (r) lateral view; (s) anterior view; (t)–(w) specimen GM DPMGI, no. 217/45, ×4.5: (t) ventral valve; (u) dorsal valve; (v) lateral view; (w) anterior view; (x) specimen GM DPMGI, no. 217/41, orna mentation, ×17; (y) specimen GM DPMGI, no. 217/46, ventral valve interior, ×9; Chersky Mountain System, TasKhayakhtakh Range, DatnaII River, right tributary of the Dogdo River, DatnaII2 section; Lower Devonian, Emsian Stage, Geremgandzha regional stage, inversus Zone, Geremgandzha Formation.
tion near the anterior margin bears up to ten ribs. Each valve area laterally of the elevation bears from ten to thirteen ribs. The dorsal valve is slightly convex or flat tened. The sulcusshaped depression starts from the umbo and widens towards anterior margin. The dorsal
valve bears six ribs in the sulcusshaped depression, two parietal ribs and up to thirteen ribs laterally of the sulcusshaped depression. S h e l l i n t e r i o r. In the ventral valve, the dental plates are absent. The dorsal valve interior is unknown.
Explanation of Plate 4 Figs. 1–5. Raisiya solonchanensis sp. nov.: (1) holotype GM DPMGI, no. 217/20, ×7.2: (1a) ventral valve; (1b) dorsal valve; (1c) lateral view; (1d) anterior view, ×3; (2) specimen GM DPMGI, no. 217/21, ×12: (2a) ventral valve; (2b) dorsal valve; (2c) lateral view; (2d) anterior view; (3) specimen GM DPMGI, no. 217/22, ×13.3: (3a) ventral valve; (3b) dorsal valve; (3c) lat eral view; (3d) anterior view; Chersky Mountain System, TasKhayakhtakh Range, right bank of Ger Creek, GeremgandzhaGer section; Lower Devonian, Emsian Stage, Geremgandzha regional stage; (4) specimen GM DPMGI, no. 217/23, ventral valve, ×9; (5) specimen GM DPMGI, no. 217/24, dorsal valve interior, ×9; central TasKhayakhtakh Mountain Ridge, left bank of the DatnaII River, DatnaII2 section; Lower Devonian, Emsian Stage, Geremgandzha regional stage, Geremgandzha Formation. Figs. 6–11. Bifida rara sp. nov.: (6) holotype GM DPMGI, no. 217/50, ×9.2: (6a) ventral valve; (6b) dorsal valve; (6c) lateral view; (6d) anterior view; (6e) microornamentation, ×18; (7) specimen GM DPMGI, no. 217/51, ×11.5: (7a) ventral valve; (7b) dorsal valve; (7c) lateral view; (7d) anterior view; (8) specimen GM DPMGI, no. 217/52, ×10.6: (8a) dorsal valve; (8b) ante rior view; (9) specimen GM DPMGI, no. 217/53, ×10.7: (9a) ventral valve; (9b) dorsal valve; (10) and (11) dorsal valve interiors, ×10: (10) specimen GM DPMGI, no. 217/54; (11) specimen GM DPMGI, no. 217/55; Selennyakhskii Range, right bank of the Talyndzha River, right bank of Gon Creek, GonI section; Lower Devonian, Emsian Stage, Nikolaevka regional stage, lower part of the Krivoi Ruchei Formation. PALEONTOLOGICAL JOURNAL
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s (а)
(b)
Fig. 4. Dorsal valve interiors of Bifida rara sp. nov.: (a) specimen GM DPMGI, no. 217/56, ×6; (b) specimen GM DPMGI, no. 217/57, ×6; Selennyakhskii Range, right bank of the Talyndzha River, right bank of Gon Creek, Gon section; Lower Devo nian, Emsian Stage, Nikolaevka regional stage, excavatus Zone, lower half of the Krivoi Ruchei Formation. Designations: (isr) inner socket ridges, (ms) median septum, (s) spires.
D i m e n s i o n s i n m m a n d r a t i o s: Specimen GM DPMGI, no. Holotype 217/40 217/41 217/42 217/43 217/44
sample, no. Т64/5 Т64/5 Т64/5 Т64/5 Т64/5
L
W
T
L/W
L/T
5.2 6.2 3.2 2.6 2.2
5.2 5.2 3.0 2.6 1.8
1.8 2.2 1.0 0.9 0.8
1.0 1.2 1.1 1.0 1.2
2.9 2.8 3.2 2.8 2.8
M a t e r i a l. Twelve satisfactorily preserved shells from the Chersky Mountain System, TasKhaya khtakh Range, left bank of the Datna II2 River, Datna II2 section, sample T64/5. S u p e r f a m i l y Dayiacea Waagen, 1883 Family Anoplothecidae Schuchert, 1894 Subfamily Anoplothecinae Schuchert, 1894 Genus Bifida Davidson, 1882 Bifida rara Baranov, sp. nov. Plate 4, figs. 6–11
E t y m o l o g y. From the Latin rarus (rare). H o l o t y p e. GM DPMGI, no. 217/50, complete shell; northeastern Eurasia, Selennyakhskii Range, right bank of the Talyndzha River, right bank of Gon Creek, Gon section; Lower Devonian, Emsian Stage, Nikolaevka regional stage, excavatus Zone, lower half of the Krivoi Ruchei Formation. D e s c r i p t i o n. The shell is very small, biconvex, and oval. The maximum width and thickness are in the middle. The cardinal extremities are rounded. The anterior commissure is intraplicate. The ornamenta
tion consists of rounded folds, which are crossed by narrow concentric lamellae with fine spines on the margins. The ventral valve is convex, with maximum thickness in the middle. The umbo is straight and pro jecting. The elevation is formed by two folds, which are widening to the anterior margin and divided by a groove with thin median rib running along its length in the middle. Each valve area laterally of the fold bears one smaller fold. The dorsal valve is less convex than the ventral valve, with maximum thickness in the mid dle. The sulcusshaped depression starts from the umbo, widens towards the anterior margin, and bears median fold in the middle starting from the umbo. The dorsal valve also bears wide lateral folds bordering sul cusshaped depression and narrow fold on the each lateral side. S h e l l i n t e r i o r (Figs. 4a, 4b). In the ventral valve, the dental plates are absent. In the dorsal valve, massive hinge plate and median septum are developed. The median septum length is three fourths of the valve length. The cardinal process is absent. The spire cones with three whorls are laterally directed. D i m e n s i o n s i n m m a n d r a t i o s: Specimen GM DPMGI, no.
sample, no.
L
W
T
L/W
L/T
Holotype 217/50 Sl102
3.8
3.6
1.0
1.05
3.8
217/51 Sl102
2.6
2.4
0.8
1.08
3.25
217/52 Sl102
2.8
2.5
0.8
1.12
3.5
217/53 Sl102
3.0
2.8
1.0
1.07
3.0
PALEONTOLOGICAL JOURNAL
Vol. 49
No. 5
2015
NEW ATRYPIDS (BRACHIOPODA) FROM THE EMSIAN (LOWER DEVONIAN)
C o m p a r i s o n. The new species differs from B. ogilviensis (Perry et al., 1974) from the Ogilvie For mation of northern Yukon (Canada) and Bifida sp. (Johnson, 1970, p. 162, pl. 43, figs. 17–27) from the Emsian of Great Basin, Nevada in the sharp folds and spines on the growth lamellae; besides, new species differs from B. ogilviensis in the absence of cardinal process. O c c u r r e n c e. Lower Devonian, Emsian Stage, Nikolaevka and Geremgandzha regional stages, exca vatus–inversus conodont zones, lower half of the Krivoi Ruchei Formation of the Selennyakhskii Range, Upper Khobochalo Subformation and Ger emgandzha Formation of the TasKhayakhtakh Range. M a t e r i a l. Ten satisfactorily preserved shells: Selennyakhskii Range, right bank of the Talyndzha River, right bank of Gon Creek: four specimens from the sample SL97 and four specimens from sample SL102; two specimens from the Chersky Mountain System, TasKhayakhtakh Mountain Ridge, right bank of Ger Creek (left tributary of the Geremgan dzha River), sample T41/1. ACKNOWLEDGMENTS The author is sincerely grateful to A.G. Stepanov for producing photographs of brachiopods. This paper was partly supported by the Russian Foundation for Basic Research, project no. 1305 00520 and Program no. 23 of the Presidium of the Russian Academy of Sciences, project no. 23.1.
PALEONTOLOGICAL JOURNAL
Vol. 49
No. 5
2015
473
REFERENCES Alekseeva, R.E., Sidyachenko, A.I., Baranov, V.V., Afa nasjeva, G.A., Grunt, T.A., Komarov, V.N., Lazarev, S.S., and Manankov, I.N., Atlas devonskikh brakhiopod severo vostoka Rossii (Vostochnaya Yakutia, Magadanskaya oblast’) (Atlas of Devonian Brachiopods of Northeastern Russia: Eastern Yakutia and Magadan Oblast), Alekseeva, R.E., Ed., Tr. Paleontol. Inst. Ross. Akad. Nauk, vol. 266, Mos cow: Nauka, 1996. Alkhovik, T.S. and Baranov, V.V., Stratigrafiya Nizhnego devona Vostochnoi Yakutii (SeveroVostok Rossii) (Stratigra phy of the Lower Devonian of Eastern Yakutia, Northeast ern Russia), Parfenov, L.M., Ed., Yakutsk: Yakut. Fil. Izd. Sib. Otd. Ross. Akad. Nauk, 2001. Chatterton, B.D.E. and Perry, D.G., An Early Eifelian invertebrate faunule, Whittaker Anticline, northwestern Canada, J. Paleontol., 1978, vol. 52, no. 8, pp. 28–39. Copper, P., Atrypida, in Treatise on Invertebrate Paleontol ogy. Part H. Brachiopoda Revised, Kaesler, R.L., Ed., vol. 4: Rhynchonelliformea (Part), Boulder (CO)–Lawrence (KS): Geol. Soc. Am.–Univ. Kansas Press, 2002, pp. 1377–1474. Johnson, J.G., Great Basin Lower Devonian Brachiopoda, Geol. Soc. Am. Mem., vol. 121, Boulder (CO): Geol. Soc. Am., 1970. Lenz, A.C., Two new Lower Devonian atrypid brachiopods from Royal Creek, Yukon Territory, Canada, J. Paleontol., 1968, vol. 42, no. 1, pp. 180–185. Perry, D.G., Klapper, G., and Lenz, A.C., Age of the Ogil vie Formation (Devonian), northern Yukon: Based prima rily on the occurrence of brachiopods and conodonts, Can. J. Earth Sci., 1974, vol. 11, no. 8, pp. 1055–1097. Savage, N.M., New atrypid brachiopods from the Lower Devonian of New South Wales, J. Paleontol., 1970, vol. 44, no. 4, pp. 655–668.
Translated by A. Madison
