ISSN 0031 0301, Paleontological Journal, 2011, Vol. 45, No. 6, pp. 634–638. © Pleiades Publishing, Ltd., 2011. Original Russian Text © V.M. Nazarova, 2011, published in Paleontologicheskii Zhurnal, 2011, No. 6, pp. 38–41.
Icriodus jejunus, a New Conodont Species from the Mosolovian Regional Stage (Middle Devonian, Eifelian Stage) of the Voronezh Anteclise V. M. Nazarova Department of Paleontology, Geological Faculty, Moscow State University, Moscow, 119991 Russia e mail: [email protected] Received March 01, 2011
Abstract—A new conodont species, Icriodus jejunus sp. nov., from the Mosolovian Regional Stage (Middle Devonian, Eifelian Stage) of the Voronezh Anteclise (central Russian Platform) is described.
Keywords: Icriodus, conodonts, new taxa, Middle Devonian, Eifelian Stage, Voronezh Anteclise, Russian Platform. DOI: 10.1134/S0031030111060128
INTRODUCTION and from borehole Trubchevsk 13 (Bryansk Region) was also used by Kononova and Kim (2001, 2005). The species Icriodus jejunus was described for the These researchers regarded the specimens described as first time in the dissertation of Nazarova (1998) based I. jejunus (Nazarova, 1998) as juvenile stages of Icrio on the material from boreholes Naryshkino 4177 in dus formosus Naz. the Orel Region and Prosvet 2P in the Bryansk Region. However, this description has not been The present study is based on reexamination of col reported in a widely accessible publication. The mate lections from boreholes Naryshkino 4177, Prosvet 2P rial from boreholes Naryshkino 4177 and Prosvet 2P and Trubchevsk 13 and additional material from bore
Serpukhov M . ok Smolensk R sha Ugra River R a . Kaluga Ryazan k O Pronya Tula River Roslavl Schekino Novomoskovsk
Morshansk Bryansk Nar Efremov 13T Orel Michurinsk Klintsy Tambov Elets Lipetsk r e v 2P i Vorona River R
h Desna River z
e
Shch-16 n o r o ver V Seim Ri Kursk Voronezh Yekaterinburg Moscow Staryi Oskol Borisoglebsk Konotop Psol River Sumy Lisak Romny Kiev Priluki Belgorod Pavlovsk Buzuluk River Ukraine Kazakhstan Vorskla R. Chisinau Rostov-on-Don Lubny 300 km Kharkov 100 km
Fig. 1. Geographical position of boreholes. Designations: (2P) borehole Prosvet 2P, (13T) borehole Trubchevsk 13T, (Nar) bore hole Naryshkino 4177, (Shch 16) borehole Shchigry 16; oval shows the boundary of the Voronezh Anteclise.
634 ICRIODUS JEJUNUS, A NEW CONODONT SPECIES 635
Lithologic Sample no. column Conodonts Stage Stage Regional Depth, m stage Givetian Staryi Oskol Reg. Super 185 Ps. ziegleri I. lindensis I. gagievi Pel. iris 231a Pol. parawebbi 206
207 sp. 209 208 211 210 234a Pel. Chernyi Yar 212 213 235a sp. nov. 215 214 216 218 217 I. jejunus I. obliquimarginatus 219 I. formosus 220 I. arconensis Ct. taljashenkoae 190 221 I. struvei 222 223 224 L. oviformis Eifelian
225 226 227 195 Mosolovian I. khalymbadzhai 233a 228 200 229
231 232 233 236a 234 235 236 237 238 vka
Klintso 205
Fig. 2. Lithologic column and distribution of conodonts in the Mosolovian and Chernyi Yar regional stages of borehole Shchigry 16. hole Shchigry 16 in the Kursk Region (Fig. 1). The P. parawebbi morphotype β Chatt., Pelekysgnathus sections of boreholes Naryshkino 4177, Prosvet 2P, sp., and Pseudobipennatus ziegleri Kon. et Kim. In and Trubchevsk 13 were described previously by addition, in borehole Naryshkino 4177, I. jejunus is Kononova and Kim (2005). The section of Upper Eif accompanied by I. gagievi Kon. et Kim; in borehole elian beds of borehole Shchigry 16 is described here Prosvet 2P, by I. khalymbadzhai Kon. et Kim; and in for the first time (Fig. 2). In all boreholes, I. jejunus boreholes Shchigry 16 and Trubchevsk 13T, by Cte occurs in beds of the Mosolovian Regional Stage. In nopolygnathus taljashenkoae Kon. et Kim. These con the strata of the underlying Klintsovka Regional Stage, odont associations corroborate the Mosolovian age of conodonts have not been recorded and the overlying enclosing beds (Nazarova, 1995, 1998; Kononova and Chernyi Yar Regional Stage lacks I. jejunus. I. jejunus Kim, 2005; Nazarova et al., 2010; Nazarova and co occurs with I. formosus Naz., I. obliquimarginathus Kononova, 2011), which corresponds to the lower part Bisch. et Ziegl., I. lindensis Wedd., I. struvei Wedd., of the kockelianus Zone of the standard scale (Ziegler Polygnathus parawebbi morphotype α Chatt., and Sandberg, 1990).
PALEONTOLOGICAL JOURNAL Vol. 45 No. 6 2011 636 NAZAROVA
Plate 8
1 2 3а 3b 4
5 67 8а8b
10а 9а 9b 10b
11а 11b 13 12а 12b
Simple conical elements of the conodont apparatus of fore, it is impossible to determine which species they icriodids co occur with specimens of I. jejunus in all bore belong to. In addition, boreholes Prosvet 2P and Shchi holes. However, the same samples have yielded platform gry 16 have yielded samples with I. jejunus and other spe elements and other species of the genus Icriodus; there cies of the genus Icriodus which lack conical elements.
PALEONTOLOGICAL JOURNAL Vol. 45 No. 6 2011 ICRIODUS JEJUNUS, A NEW CONODONT SPECIES 637
Explanation of Plate 8 Eifelian Stage, Mosolovian Regional Stage, all specimens at 100× magnification. Figs. 1–13. Icriodus jejunus sp. nov.: (1) specimen MGU, no. 272/748, top view; Bryansk Region, borehole Trubchevsk 13T, 352 m of depth, sample 13T/98; (2) specimen MGU, no. 272/551, top view; Bryansk Region, borehole Prosvet 2P, 321.2 m of depth, sample 2P 47; (3) specimen MGU, no. 272/550: (3a) top and (3b) lateral views; Orel Region, borehole Naryshkino 4177, 346.4 m of depth, sample Nar 161; (4) specimen MGU, no. 272/549, top view; the same locality; 346.4 m of depth, sample Nar 161; (5) specimen MGU, no. 272/548, underside view; Bryansk Region, borehole Prosvet 2P, 321.2 m of depth, sample 2P 47; (6) specimen MGU, no. 272/552, lateral view; the same locality, 321.2 m of depth, sample 2P 47; (7) specimen MGU, no. 272/553, top view; the same locality, 321.2 m of depth, sample 2P 47; (8) specimen MGU, no. 272/749: (8a) top and (8b) underside view; Kursk Region, borehole Shchigry 16, 189.25 194.15 m of depth, sample Shch 16/223; (9) specimen MGU, no. 272/752: (a) top and (b) lateral views; the same locality and depth, sample Shch 16/223; (10) specimen MGU, no. 272/751: (a) and (b) lateral views; the same locality and depth, sample Shch 16/219; (11) specimen MGU, no. 272/753: (a) top and (b) lateral views; the same locality and depth, sample Shch 16/221; (12) holotype MGU, no. 272/750: (a) top and (b) lateral views; the same locality and depth, sample Shch 16/221; (13) specimen MGU, no. 272/754, top view; the same locality and depth, sample Shch 16/223.
SYSTEMATIC PALEONTOLOGY ticles are displaced slightly anteriorly relative to lateral Genus Icriodus Branson et Mehl, 1938 denticles). Denticles of the middle row are obtuse apical, ovate in section, extending along the platform Icriodus jejunus Nazarova, sp. nov. axis. Lateral denticles are thin, pointed, circular in Plate 8, figs. 1–13 cross section, and ranging in number from 5 to 8. The I. jejunus (nomen nudum): Nazarova, 1998, p. 19. last 2 or 3 pairs of lateral denticles are poorly devel I. formosus: Kononova and Kim, 2001, pl. 7, fig. 1, non figs. 2–4 oped. They are lower than respective denticles of the =I. formosus; Kononova and Kim, 2005, pl. 3, fig. 5, non figs. 6–18 =I. formosus. middle row and positioned on the slopes of lateral Etymology. From the Latin jejunus (belly parts of the middle row. On the external side of the ele pinched). ment, they are even lower or absent. Probably, this structure should be regarded as analogue of a free row. H o l o t y p e. MGU (Moscow State University), The posterior end of the middle row has a single tooth no. 272/750, I element; Kursk Region, 20 km north (main cusp), which does not correspond to denticles west of the town of Shchigry, borehole Shchigry 16, of lateral rows (true free row). It is lower than others, 189.25–194.15 m of depth, sample Shch 16/221; Eif claw shaped; its base is inclined posteriorly, with its elian Stage, Mosolovian Regional Stage. pointed apex turned upwards. The basal cavity is D e s c r i p t i o n. I element is small, narrow, spin small, teardrop shaped, slightly asymmetrical; its dle shaped in top view (Fig. 3). The longitudinal axis flanks have even rounded margins and extend beyond is slightly sigmoidal, with the greatest bend in the pos the platform. terior part of the platform. In lateral view, the posterior part of the platform is arched slightly downwards. The Measurements in μm. Platform length, 250– denticles are equal in height, alternating (medial den 410; platform width, 45–100.
internal top viewexternal undersideside view side denticles denticles basal of middle of lateral cavity row rows
flanks
low denticles main of lateral cusp row
Fig. 3. Morphology of platform elements of the genus Icriodus.
PALEONTOLOGICAL JOURNAL Vol. 45 No. 6 2011 638 NAZAROVA
Comparison. Icriodus jejunus is similar to REFERENCES I. brevis Stauffer and I. lindensis Weddige in the nar Kononova, L.I. and Kim, S. E, Eifelian Icriodids (Con row platform and alternating denticles and differs in odonts) from the Bryansk Region and Their Ontogeny, the low posterior lateral denticles and the claw shaped Paleontol. Zh., 2001, no. 5, pp. 64–69 [Paleontol. J., 2001, main cusp. It is similar to juvenile stages of I. formosus vol. 35, no. 5, pp. 514–520]. Kononova, L.I. and Kim, S. Y., Eifelian Conodonts from in the low posterior lateral denticles and differs from it the Central Russian Platform, Paleontol. J., 2005, vol. 39, in the narrower platform and pointed and detached no. Suppl. 2, pp. S55–S134. denticles. Nazarova, V.M., Icriodids (Conodonts) from the Eifelian and Frasnian Beds of the Central Russian Platform, in Bio O c c u r r e n c e. Eifelian Stage, Mosolovian stratigrafiya srednego verkhnego paleozoya Russkoi plat Regional Stage (kockelianus Zone) of southwestern formy i skladchatykh oblastei Urala i Tyan’ Shanya (Bios European Russia. tratigraphy of the Middle–Upper Paleozoic of the Russian Platform and the Folded Regions of the Ural and Tien Shan M a t e r i a l. Thirty six specimens from the Orel Mountains), Moscow: VNIGNI, 1995, pp. 136–144. Region, borehole Naryshkino, 4177, 346.4 m of Nazarova, V.M., Conodonts of the Middle and Late Devo depth, sample Nar 161 (1 specimen); Bryansk nian of Central European Russia (Group Icriodus), Region, borehole Prosvet 2P, 321.5 m of depth, sample Extended Abstract of Cand. Sci. (Geol.–Mineral.) Disserta 2P 47 (3 specimens); 320.0 m of depth, sample 2P 49 tion, Moscow: Mosc. State Univ., 1998. Nazarova, V.M. and Kononova, L.I., Late Eifelian Con (1 specimen); 319.2 m of depth, sample 2P 51 (2 spec odonts of the Southwestern Wing of the Voronezh Anteclise, imens); 316.5 m of depth, sample 2P 57 (1 specimen); in Paleostrat 2011. Moskva 24–26 yanvarya 2011 g. Tezisy 313.9 m of depth, sample 2P 64 (1 specimen); 313.5 m dokladov (Paleostrat 2011: Theses of Reports, Moscow, of depth, sample 2P 65 (4 specimens); 313.1 m of January 24–26, 2011), Moscow: Paleontol. Inst. Ross. depth, sample 2P 67 (4 specimens); 312.7 m of depth, Akad. Nauk, 2011, pp. 49–50. Nazarova, V.M., Kononova, L.I., and Kharitonov, S.Yu., sample 2P 69 (2 specimens); 312.3 m of depth, sample Conodonts and Auloporids from the Middle Devonian Sec 2P 70 (3 specimens); borehole Trubchevsk 13T, 345– tion of Borehole Shchigry 16 (Kursk Region), in Paleo 353 m of depth, sample 13T/98 (4 specimens); sample strat 2010. Moskva 25–26 yanvarya 2010 g. Tezisy dokladov 13T/92 (1 specimen), sample 13T/91 (3 specimens). (Paleostrat 2010: Moscow, January 25–26, 2010: Theses of Kursk Region, borehole Shchigry 16, 189.25–194.15 m Reports), Moscow: Paleontol. Inst. Ross. Akad. Nauk, 2010, pp. 36–37. of depth, sample Shch 16/223 (3 specimens); sample Ziegler, W. and Sandberg, C.A., The Late Devonian Stan Shch 16/221 (2 specimens), sample Shch 16/219 dard Conodont Zonation, Cour. Forsch. Senckenb., 1990, (1 specimen). vol. 121, pp. 1–115.
PALEONTOLOGICAL JOURNAL Vol. 45 No. 6 2011