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Paleontological Journal

, 45:567 | Cite as

On the morphology and taxonomic position of Ungulaspis arctoa (Osteostraci, Agnatha) from the lower devonian of the Severnaya Zemlya archipelago

  • O. B. Afanassieva
Article

Abstract

An additional study of the cephalic shield and trunk scales of the holotype of Ungulaspis arctoa Afanassieva et Karatajūtė-Talimaa has shown that the exoskeleton surface is composed of dentin of at least two generations. Based on new data, the exoskeleton of Ungulaspis is reconstructed. A model for ontogenetic development of the exoskeleton of Ungulaspis arctoa is proposed. The superposition growth of osteostracan exoskeleton is described in detail for the first time using macro-rather than microremains. Using Osteostraci as an example, the existence of two (bipolar and unipolar) types of vertical growth of the exoskeleton in some groups of lower vertebrates is shown. The taxonomic position of Ungulaspis arctoa in the system of Osteostraci is discussed.

Keywords

Agnatha osteostracans Ungulaspis morphology Lower Devonian Severnaya Zemlya Archipelago Russia 

References

  1. Afanassieva, O.B., Cephalaspids (Agnatha) of the Soviet Union, Tr. Paleontol. Inst. Akad. Nauk SSSR, 1991, vol. 248, pp. 1–144.Google Scholar
  2. Afanassieva, O.B., The Exoskeleton of Ungulaspis and Ateleaspis (Osteostraci, Agnatha) from the Lower Devonian of Severnaya Zemlya, Russia, Acta Geol. Polon., 1999, vol. 49, no. 2, pp. 119–123.Google Scholar
  3. Afanassieva, O.B., New Osteostracans from the Silurian of Severnaya Zemlya Archipelago (Russia) and Some Problems Relating to the Parataxonomy of Armored Agnathans, Paleontol. J., 2000, vol. 34, no. Suppl. 2, pp. S138–S146.Google Scholar
  4. Afanassieva, O.B., New Evidence on the Exoskeletal Growth of Some Lower Devonian Osteostracans, in 10th International Symposium on Early Vertebrates/Lower Vertebrates: Gramado, May 24–28, 2004: Programme and Abstracts, Richter, M., Ed., Gramado: Univ. Federal Rio Grande Sul., 2004a, p. 9.Google Scholar
  5. Afanassieva, O.B., Microrelief on the Exoskeleton of Some Early Osteostracans (Agnatha): Preliminary Analysis of Its Significance, Acta Univ. Latvi., Earth Environ. Sci., 2004b, vol. 679 (The Gross Symposium 2: Advances in Palaeoichthyology: Riga, Latvia, Luksevics, E., Ed.), pp. 14–21.Google Scholar
  6. Afanassieva, O.B., Osteostracans (Osteostraci), in Iskopaemye pozvonochnye Rossii i sopredel’nykh stran. Beschelyustnye i drevnie ryby (Fossil Vertebrates of Russia and Adjacent Countries: Agnathans and Early Fishes), Novitskaya, L.I, and Afanassieva, O.B., Eds., Moscow: GEOS, 2004c, pp. 210–268.Google Scholar
  7. Afanassieva, O.B. and Karatajūtė-Talimaa, V.N., New Osteostracans (Agnatha) from the Silurian and Lower Devonian of the Severnaya Zemlya Archipelago (Russia), Paleontol. Zh., 1998, no. 6, pp. 60–64 [Paleontol. J., 1998, vol. 32, no. 6, pp. 605–610].Google Scholar
  8. Gross, W., Aufbau des Panzers obersilurischer Heterostraci und Osteostraci Norddeutschlands (Geschiebe) und Oesels, Acta Zool., 1961, vol. 42, pp. 73–150.CrossRefGoogle Scholar
  9. Janvier, P., Les Céphalaspides du Spitsberg. Anatomie, phylogénie et systématique des Ostéostracés siluro-dévoniens: Révision des Ostéostracés de la Formation de Wood Bay (Dévonian inférieur du Spitsberg), Paris: Cahiers Paléontol. CNRS, 1985.Google Scholar
  10. Janvier, P., Early Vertebrates: Oxford Monographs on Geology and Geophysics, Oxford: Clarendon Press, 1996.Google Scholar
  11. Mark-Kurik, E. and Janvier, P., Early Devonian Osteostracans from Severnaya Zemlya, Russia, J. Vertebr. Paleontol., 1995, vol. 15, no. 3, pp. 449–462.CrossRefGoogle Scholar
  12. Novitskaya, L.I, On the Diagnostic Significance of Ornamentation in Agnathans and Fishes, Paleontol. Zh., 1971, no. 4, pp. 82–96.Google Scholar
  13. Ørvig, T., Histologic Studies of Placoderms and Fossil Elasmobranchs: 1. The Endoskeleton, with Remarks on the Hard Tissues of Lower Vertebrates in General, Arkiv Zool., 1951, vol. 2, no. 2, pp. 321–454.Google Scholar
  14. Stensiö E., The Downtonian and Devonian Vertebrates of Stensi Spitsbergen: Part 1. Family Cephalaspidae, Scrift. Svalbard Nordishav., 1927, vol. 12, pp. 1–391.Google Scholar
  15. Vergoossen, J.M.J., Late Silurian Fish Microfossils from Ramsåsa, Locality H, Skania, South Sweden, with Some Remarks on the Body Zonation Scheme Used in Thelodont Studies, Scr. Geol., 2002, vol. 123, pp. 41–69.Google Scholar
  16. Vergoossen, J.M.J., Fish Microfossils from the Upper Silurian Sved Sandstone Formation, Skåne, Southern Sweden, Scr. Geol., 2003, vol. 126, pp. 1–78.Google Scholar
  17. Vergoossen, J.M.J., Fish Microfossils from Ramsåsa, Site E, Skäne, Southern Sweden (Mid Palaeozoic), Scr. Geol., 2004, vol. 127, pp. 1–70.Google Scholar
  18. Wängsjö, G., The Downtonian and Devonian Vertebrates of Spitsbergen: Part 9. Morphologic and Systematic Studies of the Spitsbergen Cephalaspids, Skrift. Norsk Polarinst., 1952, no. 97, pp. 1–657.Google Scholar

Copyright information

© Pleiades Publishing, Ltd. 2011

Authors and Affiliations

  1. 1.Borissiak Paleontological InstituteRussian Academy of SciencesMoscowRussia

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