Revised description of the genus Pseudobipennatus Kononova et Kim (Conodonta, Middle Devonian)

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  • ISSN 00310301, Paleontological Journal, 2014, Vol. 48, No. 3, pp. 310316. Pleiades Publishing, Ltd., 2014.Original Russian Text L.I. Kononova, V.M. Nazarova, 2014, published in Paleontologicheskii Zhurnal, 2014, No. 3, pp. 8790.

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    INTRODUCTION

    The genus Pseudobipennatus, with the only speciesP. ziegleri was described for the first time from theMosolovian Regional Stage (Eifelian Stage, MiddleDevonian) of the Voronezh Anteclise (Kononova andKim, 2005). The type series consisted of 17 specimens.

    The species P. ziegleri is a typical member of conodont associations of the Mosolovian Regional Stage(Nazarova and Kononova, 2012a); it is easy to identifyand, hence, characterized by a significant correlationpotential within the Voronezh Anteclise.

    In addition to the type series, the material of P. ziegleri includes specimens from boreholes in the KurskRegion, i.e., Shchigry16 (Nizhnekrasnoe) (Nazarova, 2011) and Shchigry19 (Osinovka) located20 km east of it. A total of 45 specimens of P. zieglerihave been examined. The sections of these boreholeswere published in previous works (Kononova andKim, 2005; Nazarova, 2011). The presence of P. ziegleri in these sections and confinement to particularconodont assemblages was also marked previously(Kononova and Kim, 2005; Nazarova and Kononova,2012a).

    In all boreholes, P. ziegleri cooccurs in theMosolovian Regional Stage with Polygnathusparawebbi Chatt., Ctenopolygnathus taljashenkoaeKon. et Kim, Icriodus formosus Naz., I. arconensisStauff., I. gagievi Kon. et Kim, I. jejunus Naz.,I. khalymbadzhai Kon. et Kim, I. lindensis Wedd.,I. struvei Wedd., Pelekysgnathus iris Gag., Pelekysgnathus sp., Belodella sp., and Coelocerodontus sp.Judging from cooccurrence of Icriodus struvei Wedd.,I. lindensis Wedd., and I. formosus Naz., the Mosolovian Regional Stage corresponds to the kockelianus

    Zone (Kononova and Kim, 2005; Nazarova andKononova, 2012a).

    The presence of an area on the upper surface in themiddle part of the denticle row was regarded as themain diagnostic character of the genus Pseudobipennatus (Fig. 1). It was an argument to regard the elements described of the genus Pseudobipennatus asplatform Paelements. A detailed study of the typeseries and additional material under SEM and opticalmicroscopes has shown that this area was formed bywear on the upper surface of the denticle row, as theelement functioned as a tooth.

    The presence of lifetime wear on conodont elements was repeatedly discussed. Donoghue and Purnell (1999) used the wear for substantiation of toothlike function of conodont elements. Weddige (1990)regarded the wear surface as a result of pathology. Ourcollections contain many worn elements of variousspecies; this phenomenon is particularly frequent inicriodontids (Nazarova and Kononova, 2012b).

    In the middle part of the denticle row of P. ziegleri,an area resembling a platform was formed during theanimals life (Figs. 1, 2). The extent of wear varies fromseveral denticles to an extensive area with a groove inthe middle. In juveniles, the area consists of only twoor three denticles and, in neighboring denticles, onlytips are worn (Pl. 16, fig. 2). In adults, wear traces arealso frequently observed on the denticles neighboringto the area (see, e.g., Fig. 2b; Pl. 16, figs. 5a, 10a). Certainly, like other conodonts, some specimens of P. ziegleri have traces of postmortem breaks of denticles.Our collection contains such specimens (Pl. 16, figs. 9,10; Pl. 17, fig. 3). However, wear marks are distinguished by the even edge of denticles which is locatedon the same line as the plane of the central area.

    Revised Description of the Genus Pseudobipennatus Kononova et Kim (Conodonta, Middle Devonian)

    L. I. Kononova and V. M. NazarovaGeological Faculty, Moscow State University, Moscow, 119992 Russia

    email: VM516@yandex.ruReceived July 26, 2012

    AbstractA detailed study of new materials of Pseudobipennatus ziegleri Kononova et Kim, 2005 has shownthat an area on the upper surface of conodont elements that was previously described as a platform is a middleworn site of the denticle row of a blade element formed as a result of normal functioning of this element as atooth rather than a structural element of the platform. Therefore, descriptions of the genus PseudobipennatusKononova et Kim, 2005 and its single species P. ziegleri Kononova et Kim, 2005 are revised.

    Keywords: Pseudobipennatus, conodonts, Middle Devonian, Eifelian

    DOI: 10.1134/S0031030114030125

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    REVISED DESCRIPTION OF THE GENUS PSEUDOBIPENNATUS 311

    Fig. 1. Morphology and terminology of blade elements of the genus Pseudobipennatus (Kononova and Kim, 2005, with changes).

    Anteriorend

    Area of worndenticles

    Basal cavity

    Denticles

    Posterior endTop view Underside view

    Lateral view

    Area of worndenticles

    DenticlesDenticles

    (a) (b)

    100 m

    Fig. 2. Fragments of worn surface of elements of Pseudobipennatus ziegleri Kon. et Kim, 400: (a) specimen MGU, no. 272/764(Pl. 16, fig. 5); (b) specimen MGU, no. 272/763 (Pl. 16, fig. 3).

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    Under an optical microscope in transmitted light,all specimens of P. ziegleri have the same denticle basesunder the area as in the anterior and posterior parts ofthe blade, where the ends of denticles are pointed andlack a trace of wear (Pl. 15, figs. 2, 3, 6a, 7; Pl. 16,figs. 1a, 3a, 4a, 5a). Thus, P. ziegleri apparentlybelongs to blade rather than platform elements. Themajority of specimens are almost identical in the basewidth of all denticles, although the denticle bases ofsome specimens are narrower in the anterior and, particularly, middle part of the blade, that is, the denticlesare more densely spaced. This undoubtedly strengthened the area, which underwent the greatest load, asfood was ground. Probably, this area could have transformed into a true platform; however, descendants of Pziegleri have not yet been recorded.

    Thus, new data require new improved descriptionof the genus and species. Plates 16 and 17 show theholotype and specimens which have not yet been published. The photographs were taken using a CamScanelectron microscope (in the Borissiak PaleontologicalInstitute of the Russian Academy of Sciences (PIN))and a Levenhuk 595 biological microscope (objective10) with a Levenhuk C310 ocular camera. The collection under study is stored at the Department ofPaleontology of Moscow State University (collectionno. 272).

    SYSTEMATIC PALEONTOLOGY

    Genus Pseudobipennatus Kononova et Kim, 2005

    Pseudobipennatus: Kononova and Kim, 2005, p. S121.

    Ty p e s p e c i e s. Pseudobipennatus ziegleriKononova et Kim, 2005; northwestern VoronezhAnteclise; Middle Devonian, Eifelian, MosolovianRegional Stage.

    D i a g n o s i s. In lateral view, element shaped asrectangular blade. Upper margin of blade having onerow of denticles. Middle part of blade usually containing elongated flat or deepened area. Basal cavity asymmetrical, long, deep, wide, extending from anterior to

    posterior end of element. Elements paired, both rightand left elements present in collection.

    The apparatus in not known. Conical, Selement,and platform elements found in the same samples maybelong to the apparatus of other genera. The positionof blade elements of Pseudobipennatus in the apparatus is not known. Therefore, the elements described inthis genus should not be referred to Pa or Pb elements.The elements of Pseudobipennatus were possibly theonly pair in the apparatus.

    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. Pseudobipennatus is similar tothe genus Bipennatus Mawson, 1993 in the rectangularshape of the blade and presence of an area in its middlepart and differs from it in the asymmetrical, long,deep, basal cavity extending from the anterior to theposterior end of the element and in the presence ofonly one denticle row.

    R e m a r k s. In the middle part of the element, thegenus Bipennatus (Fig. 3) has an almost flat shapedbasal cavity with earlike lobes (Mawson, 1993), thatis, lateral flanks. This genus, represented by Pa elements, was established based on the position of thebasal cavity in the middle part of the element and thepresence of two rows of nodose denticles separated bya thin median ridge or a shallow trough (Mawson,1993). Initially, it was considered to include two species, B. bipennatus (Bisch. et Ziegl., 1957) (Eifelianand Givetian of Europe, North America, and Australia) and B. palethorpei (Telford, 1975) (UpperEmsianLower Eifelian of Australia), which were previously assigned to either Spathognathodus Branson etMehl, 1941 or Eognathodus Philip, 1965. Apparently,the genera Bipennatus and Pseudobipennatus are notrelated and they are similar because of homeomorphy.

    Pseudobipennatus ziegleri Kononova et Kim, 2005

    Plate 15, figs. 110; Plate 16, figs. 15

    Pseudobipennatus ziegleri: Kononova and Kim, 2005, p. S121,pl. 1, figs. 510, pl. 2, figs. 13.

    E x p l a n a t i o n o f P l a t e 1 5

    Western Voronezh Anteclise; Eifelian Stage, Mosolovian Regional Stage; all specimens at 120magnification, except for Figs. 5band 10a.Figs. 110. Pseudobipennatus ziegleri Kon. et Kim, 2005: (1) holotype PIN, no. 50241: (1a) lateral, (1b) top, and (1c) undersideviews; Orel Region, borehole Naryshkino 4177, 343.3 m of depth, sample Nar155; (2) specimen MGU, no. 272/758, lateral viewin transmitted light; Bryansk Region, borehole Prosvet 2P, 321.5 m of depth, sample 2P47; (3) specimen MGU, no. 272/765,lateral view in transmitted light; Bryansk Region, borehole Prosvet 2P, 313.5 m of depth, sample 2P65; (4) specimen MGU,no. 272/766, lateral view; Kursk Region, borehole Shchigry16, 18.25194.15 m of depth, sample SHCH16/223; (5) specimenMGU, no. 272/767: (5a) top view, (5b) fragment with worn surface, 240; (5c) underside view; Kursk Region, borehole Shchigry16, 189.25194.15 m of depth, sample SHCH16/222; (6) specimen MGU, no. 272/762: (6a) lateral view in transmitted light,(6b) lateral view; Kursk Region, borehole Shchigry19, 180.0184.9 m of depth, sample SHCH19/190; (7) specimen MGU,no. 272/759, lateral view in transmitted light; Bryansk Region, borehole Prosvet 2P, 321.5 m of depth, sample 2P47; (8) specimen MGU, no. 272/768, lateral view; Kursk Region, borehole Shchigry16, 184.35189.25 m of depth, sample SHCH16/207;(9) specimen MGU, no. 272/769: (9a) lateral and (9b) top views; Kursk Region, borehole Shchigry16, 189.25194.15 m ofdepth, sample SHCH16/222; (10) specimen MGU, no. 272/770: (10a) lateral view, fragment with worn surface, 240,(10b) lateral view, (10c) top view; Kursk Region, borehole Shchigry16, 184.35189.25 m of depth, sample SHCH16/211.

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    Plate 15

    100 m

    1a 1b 1c

    2 34

    6a 6b

    5a

    5b

    5c

    78

    9b10a

    10b 10c9a

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    Plate 16

    100 m

    1a 1b 1c 2

    3a 3b 3c 4a 4b

    5a 5b 5c

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    H o l o t y p e. PIN, no. 50241, left Pa element;Orel Region, village of Naryshkino, borehole 4177,343.3 m of depth, sample Nar155; Eifelian,Mosolovian Regional Stage, kockelianus Zone,Beds with Icriodus formosusPolygnathus parawebbi;Kononova and Kim, 2005, pl. 1, fig. 5; refigured here(Pl. 16, fig. 1).

    D e s c r i p t i o n (Fig. 2). The blade element isdentate. The longitudinal axis of the element is arcuate. The upper edge is almost parallel to the loweredge. The denticles are fused at the base, only theirpointed apical ends are free. The denticle bases areformed of lighter (dark in transmitted light) matter;therefore, in lateral view, a wide light band extendsalong the entire element. The total number of denticles ranges from 11 to 16, rarely, up to 20. The denticles are usually equal in height, although anterior denticles may be slightly higher than posterior denticles.Because of denticle wear, the middle part of the uppersurface of the element usually has a flat area from one

    fifth to onethird of the element length (this is from 2to 9, usually 6, worn denticles); sometimes, the areahas a superficial longitudinal groove. The basal cavityis wide, with the greatest width in the middle part ofthe element or closer to the posterior end.

    M e a s u r e m e n t s in m. Element length, 330610; height (in lateral view), 170230.

    O c c u r r e n c e. Russia, Voronezh Anteclise; Eifelian Stage, Mosolovian Regional Stage.

    M a t e r i a l. Fortyfive variously preserved specimens; Orel Region, borehole Naryshkino 4177,344.4 m of depth, sample Nar157 (1 specimen);343.3 m of depth, sample Nar155 (7 specimens);346.4 m of depth, sample Nar161 (1 specimen); Bryansk Region, borehole Prosvet 2P, 321.5 m of depth,sample 2P47 (4 specimens); 313.9 m of depth, sample2P64 (1 specimen); 313.5 m of depth, sample 2P65(4 specimens); borehole Trubchevsk 13T, 345353 mof depth, sample 13T/93 (3 specimens); KurskRegion, borehole Shchigry16 (Nizhnekrasnoe),

    E x p l a n a t i o n o f P l a t e 1 6

    Kursk Region, southwestern Voronezh Anteclise; Eifelian Stage, Mosolovian Regional Stage; all specimens at 120 magnification.Figs. 15. Pseudobipennatus ziegleri Kon. et Kim, 2005 : (1) specimen MGU, no. 272/761: (1a) lateral view in transmitted light,(1b) lateral view, (1c) top view; Kursk Region, borehole Shchigry19, 189.8194.7 m of depth, sample SHCH19/204; (2) specimen MGU, no. 6031003, top view; Kursk Region, borehole Shchigry16, 184.35189.25 m of depth, sample SHCH16/217;(3) specimen MGU, no. 272/763: (3a) lateral view in transmitted light, (3b) lateral view, and (3c) top view; Kursk Region, borehole Shchigry19, 180.0184.9 m of depth, sample SHCH19/190; (4) specimen MGU, no. 272/760: (4a) lateral view in transmitted light and (4b) top view; Kursk Region, borehole Shchigry19, 189.8194.7 m of depth, sample SHCH19/207; (5) specimen MGU, no. 272/764: (5a) lateral view in transmitted light, (5b) lateral view, and (5c) top view; Kursk Region, boreholeShchigry19, 18.0184.9 m of depth, sample SHCH19/190.

    Fig. 3. Morphology and terminology of Pa elements of the genus Bipennatus.

    Anteriorend

    Denticles

    Basal cavity

    Posteriorend

    Top Underside

    Nodes

    Flanks

    Groove

    viewview

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    189.25194.15 m of depth, sample SHCH16/223(1 specimen), sample SHCH16/222 (2 specimens),sample SHCH16/220 (1 specimen); 184.35189.25 mof depth, sample SHCH16/217 (1 specimen), sampleSHCH16/216 (2 specimens), sample SHCH16/215(2 specimens), sample SHCH16/214 (1 specimen),sample SHCH16/211 (1 specimen), sample SHCH16/209 (1 specimen), sample SHCH16/207 (3 specimens), sample SHCH16/206 (1 specimen); boreholeShchigry19 (Osinovka), 189.8194.7 m of depth,sample SHCH19/207 (1 specimen), sample SHCH19/204 (1 specimen); 184.9189.8 m of depth, sampleSHCH19/200 (1 specimen), sample SHCH19/199(1 specimen); 180.0184.9 m of depth, sample SHCH19/190 (4 specimens).

    ACKNOWLEDGMENTS

    We are grateful to I.S. Barskov (Moscow State University), who gave inspiration to our study, and toA.S. Alekseev (PIN) for valuable remarks.

    REFERENCES

    Donoghue, P.C.J. and Purnell, M.A., Mammallike occlusion in conodonts, Palaeobiology, 1999, vol. 25, no. 1,pp. 5874.Kononova, L.I. and Kim, S.Y., Eifelian conodonts fromthe central Russian Platform, Paleontol. J. (Moscow), 2005,vol. 39, no. suppl. 2, pp. 55134.

    Mawson, R., Bipennatus, a new genus of midDevonianconodonts, Mem. Ass. Austral. Palaeontol., 1993, no. 15,pp. 137140.

    Nazarova, V.M., Icriodus jejunus, a new conodont speciesfrom the Mosolovian Regional Stage (Middle Devonian,Eifelian Stage) of the Voronezh Anteclise, Paleontol. Zh.,2011, no. 6, pp. 3841.

    Nazarova, V.M. and Kononova, L.I., Conodont characteristics of the Mosolovian Regional Stage (Middle Devonian)of the western part of the Voronezh Anteclise, in Tezisydokladov Paleostrat2012. Godichnoe sobranie sektsii paleontologii MOIP i Moskovskogo otdeleniya Paleontologicheskogo obshchestva. Moskva, 30 yanvarya1 fevralya2012 g. (Theses of Reports Paleostrat2012: Annual Meeting of the Paleontological Section of Moscow Society ofNature Explorers and Moscow Department of the Paleontological Society, Moscow, January 30February 1, 2012),Alekseev, A.S., Ed., Moscow: Paleontol. Inst. Ross. Akad.Nauk, 2012a, p. 47.

    Nazarova, V.M. and Kononova, L.I., Traces of lifetime damage on the surface of conodont elements, in Lomonosovskiechteniya2012. Moskva, 1721 aprelya 2012 g. (LomonosovConference2012: Moscow, April 1721, 2012), Moscow:Mosk. Gos. Univ., 2012b (http://geo.web.ru/pubd//2012/06/01/0001186421/pdf/nazarova_kononova_2012.pdf).

    Weddige, K., Pathological conodonts, Cour. Forschungsinst.Senckenberg, 1990, vol. 118, pp. 563589.

    Translated by G. Rautian