ISSN 00310301, Paleontological Journal, 2013, Vol. 47, No. 2, pp. 185–189. © Pleiades Publishing, Ltd., 2013. Original Russian Text © T.Yu. Tolmacheva, 2013, published in Paleontologicheskii Zhurnal, 2013, No. 2, pp. 55–59.
A New Middle Ordovician Conodont from Central Kazakhstan, Nothern Kyrgyzstan, and Altai T. Yu. Tolmacheva Karpinsky AllRussia Geological Research Institute, Srednii pr. 74, St. Petersburg, 199106 Russia email:
[email protected] Received January 28, 2011
Abstract—Naimanodus degtyarevi gen. et sp. nov., a new conodont genus and species from the Lower Darri wilian (Middle Ordovician) limestones of the Naiman Formation in central Kazakhstan is described. Three types of coniform nongeniculate elements are identified in the apparatus of this species. The new species was widespread in the Asian Paleobasin and recorded in three localities in Kazakhstan, eastern Kyrgyzstan, and Altai. Keywords: conodonts, Middle Ordovician, Kazakhstan, Kyrgyzstan, Altai DOI: 10.1134/S0031030113020147
INTRODUCTION The taxonomic composition of Ordovician con odont assemblages from the western part of the Cen tral Asia Folded Belt is still insufficiently studied (Gridina and Mashkova, 1977; Kurkovskaya, 1985; Zhylkaidarov, 1998; Dubinina, 2000; Tolmacheva et al., 2004; etc). In Kazakhstan, Middle Ordovician conodont assemblages from cherts are taxonomically poor, whereas conodonts from carbonate deposits are almost unknown, although, during that period, con odont faunas are characterized by high taxonomic diversity in all continents (Löfgren, 1978; Zhen et al., 2009). Only recently, the first data on conodonts from Middle Ordovician carbonates from Central Asia were obtained. Relatively shallow water carbonates of this age have yielded conodont assemblages including both cosmopolitan species and a number of previously unknown taxa. The difference in taxonomic composi tion between the shallowwater conodont assemblages from limestones and those from deeper water cherts noticed in previous studies (Zhylkaidarov, 1998; Dubi nina, 2000) was confirmed. This paper describes a new conodont genus and species, Naimanodus degtyarevi gen. et sp. nov., which was found in three localities in Central Kazakhstan, northern Kyrgyzstan, and Gorny Altai (Fig. 1). It is possible that the geographical range of N. degtyarevi was not restricted to the Central Asian Basin, since similar elements were reported from the lowermost Middle Ordovician in central Newfound land, Canada (Nowlan and Thurlow, 1984). The best preserved elements, including one desig nated as the holotype, come from limestones of the Naiman Formation in its stratotype section (48°54′57′′ N, 79°00′20′′ E) in the Chingiz Range of the eastern part of Central Kazakhstan (Nikitin,
1972). The Naiman Formation is composed mostly of siliciclastics and only its upper part contains a 15m thick limestone bed. The formation was dated by the graptolites Phyllograptus typus (Hall) and Paraglos sograptus tentaculatus (Finney et Skevington) as the Late Arenigian–Early Llanvirnian (Nikitin, 1972; Orlova, 1994). This age was confirmed by the con odonts Periodon zgierzensis Dzik, Drepanodus arcuatus Pander, and Dapsilodus mutatus (Barson et Mehl) which were found by A.R. Orlova and identified by S.V. Dubinina (Orlova, 1994).
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Fig. 1. Geographical position of localities of N. degtyarevi sp. nov.: (1) outcrop in the Naiman valley; (2) outcrop in the Kentash and Chong KokKya ckeeks basin; (3) out crop on the right bank of the Baranii Creek.
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A recent layerbylayer sampling of limestones of the Naiman Formation revealed that the major part of carbonates is barren of conodonts or they are scarce. Only the uppermost 30cmthick layer of dark gray finebedded limestones and cherty mudstones yielded hundreds of conodont elements. The conodont assemblage obtained consists of more than 30 species and is dominated by Periodon macrodentata (Graves et Ellison) and Paroistodus horridus (Barnes et Poplawski). The elements of Naimanodus degtyarevi gen. et sp. nov. are very sparse, composing less than 1% of the total number of specimens. Three specimens of N. degtyarevi gen. et sp. nov. were found in the upper part of the Kentash Formation in the locality on the southern slope of the western part of the Kyrgyz Range in the Kentash and Chong Kok Kya creeks basin north of the village of Kepyure Bazaar, northern Kyrgyzstan (Apayarov et al., 2008). The upper part of the Kentash Formation consists mostly of volcanic and volcanoclastic deposits, with rare limestone interbeds and lenses. One of limestone lenses (42°31′31.20′′ N, 72°51′56.40′′ E) has yielded several tens of conodonts, including Panderodus? nog amii (Lee), Ansella robusta (Ethington et Clark), Jua nognathus variabilis Serpagli, D. arcuatus Pander, His tiodella holodentata Ethington et Clark, and N. degt yarevi gen. et sp. nov. The age is determined by the occurrence of H. holodentata and A. robusta, which are typical for the Early Darriwilian (Ethington and Clark, 1981). Many specimens of N. degtyarevi gen. et sp. nov. were found in limestones in the upper part of the Vosk resensk Formation, the type section of which outcrops on the right bank of the Baranii Creek near the village of Ust’Chagyrka in the Gorny Altai (Petrunina, 1984). The formation is more than 300 m thick, dom inated by siliciclastics and roofed by a thinlayer lime stone bed rich in macrofauna. Brachiopods and trilo bites from this section suggested the Late Dapinian– Early Darriwilian age (Petrunina, 1984). Conodonts are abundant, but most of them are poorly preserved coniform elements, among which N. degtyarevi gen. et sp. nov. comprises less than 5% of the whole assem blage. At present, a suprageneric classification for simple cone conodonts proposed in the Treatise (Clark et al.,
1981) and amended by subsequent studies (Dzik, 1991; Sansom et al., 1995; Sweet and Donoghue, 2001) is the most widely used and applied here. In contrast to classification for platform and ramiform conodonts, the systematic identity of simple coniform species with restricted set of morphological characters and obscure homology of elements are provisional (Donoghue et al., 2008). All elements are described using the notation scheme widely used for elements of the genus Pan derodus (Sansom et al., 1995; Leslie, 2000). The spec imens figured (coll. no. 13218) are stored in the Chernyshev Central Research Geological Museum (TsNIGR Museum), AllRussia Geological Research Institute, St. Petersburg, Russia. SYSTEMATIC PALEONTOLOGY CLASS CONODONTA Order Panderodontida Family Panderodontidae Lindström, 1970 Genus Naimanodus Tolmacheva, gen. nov.
E t y m o l o g y. From the Naiman Formation. Ty p e s p e c i e s. Naimanodus degtyarevi sp. nov. D i a g n o s i s. Coniform elements with high base, long slightly inclined cusp, anterior and two postero lateral longitudinal keels. Cross section of elements triangular. Flat posterior side having deep longitudinal furrow. Apparatus of Naimanodus composed of three element morphotypes: (1) thin elongated elements with variably twisted base (Figs. 2a, 2b); (2) thin, elon gated symmetrical elements (Fig. 2c); and (3) com pressed, almost symmetrical (subsymmetrical) ele ments with furrow on posterior side (Fig. 2d). C o m p o s i t i o n. Type species. C o m p a r i s o n. Elements of Naimanodus gen. nov. are similar in gross morphology to that of Pan derodus Ethington, 1959 (Fig. 2f). Both genera are characterized by the presence of compressed and elongated element types. Naimanodus differs from Panderodus in the wellpronounced posterolateral keels and posterior furrow, which in Panderodus ele ments is always in the lateral position. Some elements of Parapanderodus Stouge, 1984 and Striatodontus Ji et Barnes, 1994 have posterior furrows (Fig. 2e); how
Explanation of Plate 12 All elements, except for Fig. 9, come from sample 0634, Naiman Formation; Chingiz Range, central Kazakhstan. Figs. 1–15. Naimanodus degtyarevi sp. nov., specimens TsNIGR Museum: (1) no. 1/13218, elongated element, lateral view, ×94; (2) no. 2/13218, elongated element, lateral view, ×88; (3) no. 3/13218, elongated element, lateral view, ×85; (4) no. 4/13218, elongated element, lateral view, ×106; (5) holotype no. 5/13218, elongated element: (5à) lateral view, ×75; (5b) posterior view, ×82; (5c) enlarged base, ×170; (6) no. 6/13218, elongated element, lateral view, ×65; (7) no. 7/13218, elongated element, poste rior view, ×86; (8) no. 8/13218, subsymmetrical elongated element, enlarged base, posterior view, ×155; (9) no. 9/13218, com pressed element, from sample. Al2, Voskresensk Formation of Gornyi Altai, lateral view, ×80; (10) no. 13/13218, elongated ele ment, photograph taken in transmitted light, lateral view, ×67; (11) no. 15/13218, symmetrical elongated element, posterior view, ×74; (12) no. 10/13218, compressed element, posterior view, ×68; (13) no. 11/13218, compressed element: (13à) lateral view, ×83; (13b) aboral view, ×90; (14) no. 14/13218, compressed element, lateral view, ×75; (15) no. 12/13218, compressed element, lateral view, ×79. PALEONTOLOGICAL JOURNAL
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(d)
(b)
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(c)
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Fig. 2. Schematic drawings of (a–d) elements (with the cross section) of N. degtyarevi sp. nov. and (e, f) similar ele ments of the genera Striatodontus Ji et Barnes, 1994 and Panderodus Ethington, 1959: (a) subsymmetrical elon gated element, (b) asymmetrical elongated element, (c) symmetrical elongated element, (d) compressed ele ment, (e) drepanodiform element, and (f) graciliform element.
ever, the apparatuses of these genera include other ele ment morphotypes, not typical for Naimanodus. Naimanodus degtyarevi Tolmacheva, sp. nov. Plate 12, figs. 1–15
Coelocerodontus? n. sp. A s. f.: Nowlan and Thurlow, 1984, p. 291, pl. 2, figs. 16 and 17.
E t y m o l o g y. In honor of K.E. Degtyarev, who helped a lot in obtaining conodonts from the Naiman Formation. H o l o t y p e. TsNIGR Museum, no. 5/13218, elongated element; central Kazakhstan, Chingiz Range, loc. 063, sample 0634; Middle Ordovician, Lower Darriwilian, Naiman Formation. D e s c r i p t i o n. Relatively small (80 to 200 µm) nongeniculate conodonts with a high base and long straight and slightly inclined cusp. The basal cavity is deep, with a distinct tip located close to the anterior side of the element (Pl. 12, fig. 10). The anterior mar gin of the basal cavity is concave. The cusp is albid beginning from the tip of the basal cavity.
All elements have wellpronounced anterior and two posterolateral keels. The posterior side of the base and cusp is more or less flattened. The lateral sides of elements are smooth and flat or slightly concave in its central or anterior parts (Pl. 12, figs. 1, 13a). The cross section of the base is triangular. The basal part of ele ments has many small longitudinal costae, which do not reach the basal margin, which remains relatively smooth (Pl. 12, fig. 6). The posterior side of elements is striated and has a longitudinal furrow, which extends from the basal margin to the tip of the cusp. It has shal low grooves or is slightly concave close to the postero lateral keels (Pl. 12, fig. 8). The apparatus include a series of elongated and dif ferent from them compressed elements. The elongated elements have a variously twisted cusp, while the pos terior furrow is positioned asymmetrically. It is possi ble that elongated elements include certain groups with different extent of cusp twisting, which is typical for Panderodus elements. However, the number of available specimens is insufficient for unequivocal rev elation of groups. The subsymmetrical elongated ele ments generally resemble the elongated elements, but differ from them in the symmetry and central position of the posterior furrow (Pl. 12, fig. 11). The compressed elements are relatively shorter, with a lower base and lower basal cavity. The anterior margin of the element is curved to a greater extent because the cusp is inclined abruptly posteriorly. The posterior furrow occupies a central position. R e m a r k s. Elements of N. degtyarevi sp. nov. from the three localities mentioned above are almost identical and differ only in the color and preservation. The greatest thermal alteration (CAI 4–4.5) is charac teristic of conodonts from the Voskresensk Formation, which are dark gray and almost opaque. The elements similar to Naimanodus were recorded from central Newfoundland (Canada), where they were identified as Coelocerodontus n. sp. A (Nowlan and Thurlow, 1984). The description of Coelocerodon tus n. sp. A contains features, such as a deep basal cav ity and presence of furrow on striated posterior ele ment side (Nowlan and Thurlow, 1984). O c c u r r e n c e. N. degtyarevi was found in three Ordovician localities within the western part of the Central Asian Folded Belt: in the Naiman Formation of central Kazakhstan, the Kentash Formation of northern Kyrgyzstan, and the Voskresensk Formation of Gorny Altai. Perhaps, the new species occurs in Newfoundland. M a t e r i a l. 15 elongated, 3 subsymmetrical elon gated, and 5 compressed elements from the Naiman Formation; 3 elongated elements from the Kentash Formation; and 32 elongated and 7 compressed ele ments from the Voskresensk Formation. PALEONTOLOGICAL JOURNAL
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ACKNOWLEDGMENTS I am grateful to K.E. Degtyarev, K.N. Shatagin, A.V. Ryazantsev, and N.V. Sennikov for the field trips in Kazakhstan, Kyrgyztan, and Gorny Altai. The study was supported by the Russian Founda tion for Basic Research, project nos. 100500973 and 100500848. REFERENCES Apayarov, F.Kh., Mambetov, A.M., Mikolaichuk, A.V., and Bashkirov, A.P., The Lower Paleozoic of the Western Part of the Kyrghyz Range (Northern Tien Shan), in Geodinamika vnutrikontinental’nykh orogenov i geoekologicheskie prob lemy. Tezisy dokladov IV mezhdunarodnogo simpoziuma (IV International Symposium on the Geodynamics of Intracontinental Orogenes and Geoecological Problems), Bishkek, 2008, pp. 82–85. Clark, D.L., Sweet, W.C., Bergström, S.M., et al., Treatise on Invertebrate Paleontology, Robison, R.A., Ed., Part W, Suppl. 2, Univ. Kansas Press, 1981. Donoghue, P.C.J., Purnell, M.A., Aldridge, R.J., et al., The Interrelationships of ‘Complex’ Conodonts (Vertebrata), J. Syst. Palaeontol., 2008, vol. 6, pp. 119–153. Dubinina, S.V., Conodonts and Zonal Stratigraphy of Boundary Deposits of the Cambrian and Ordovician, Tr. Geol. Inst. Ross. Akad. Nauk, 2000, vol. 517, pp. 1–239. Dzik, J., Evolution of Oral Apparatuses in the Conodont Chordates, Acta Palaeontol. Polon., 1991, vol. 36, pp. 265– 323. Ethington, R.L. and Clark, D.L., Lower and Middle Ordovician Conodonts from the Ibex Area Western Millard County, Utah, Brigham Young Univ. Geol. Stud., 1981, vol. 28, pp. 1–160. Gridina, N.M. and Mashkova, T.V., Conodonts in the Sili ceous–Terrigenous Strata of the Atasuiskii Anticlinorium, Izv. Akad. Nauk Kaz. SSR, Ser. Geol., 1977, no. 6, pp. 47–48. Kurkovskaya, L.A., Conodont Assemblages from the Sili ceous and Siliceous–Volcanogenic Strata from the Ordovi cian of Central Kazakhstan, in Geologiya rannegeosinkli nal’nykh kompleksov Kazakhstana (Geology of the Early Geosynclinal Complexes of Kazakhstan), Moscow: Mosk. Gos. Univ., 1985, pp. 164–177.
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