Ultimate Eocene (Priabonian) chondrichthyans (Holocephali, Elasmobranchii) of Antarctica

ABSTRACT

The Eocene La Meseta Formation on Seymour Island, Antarctic Peninsula, is known for its remarkable wealth of fossil remains of chondrichthyans and teleosts. Chondrichthyans seemingly were dominant elements in the Antarctic Paleogene fish fauna, but decreased in abundance from middle to late Eocene, during which time remains of bony fishes increase. This decline of chondrichthyans at the end of the Eocene generally is related to sudden cooling of seawater, reduction in shelf area, and increasing shelf depth due to the onset of the Antarctic thermal isolation. The last chondrichthyan records known so far include a chimeroid tooth plate from TELM 6 (Lutetian) and a single pristiophorid rostral spine from TELM 7 (Priabonian). Here, we present new chondrichthyan records of Squalus, Squatina, Pristiophorus, Striatolamia, Palaeohypotodus, Carcharocles, and Ischyodus from the upper parts of TELM 7 (Priabonian), including the first record of Carcharocles sokolovi from Antarctica. This assemblage suggests that chondrichthyans persisted much longer in Antarctic waters despite rather cool sea surface temperatures of approximately 5°C. The final disappearance of chondrichthyans at the Eocene–Oligocene boundary concurs with abrupt ice sheet formation in Antarctica. Diversity patterns of chondrichthyans throughout the La Meseta Formation appear to be related to climatic conditions rather than plate tectonics.

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Citation for this article: Kriwet, J., A. Engelbrecht, T. Mörs, M. Reguero, and C. Pfaff. 2016. Ultimate Eocene (Priabonian) chondrichthyans (Holocephali, Elasmobranchii) of Antarctica. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1160911.

ACKNOWLEDGMENTS

We would like to thank J. Hagström (NRM) and J. Moly (MLP) for assistance in the field. The Argentinian Antarctic Institute (IAA-DNA), Argentinian Air Force, and Swedish Polar Research Secretariat (SPFS) are acknowledged for logistic support for field work on Seymour Island. We are grateful to Z. Johanson and E. Bernard (Natural History Museum London) for the possibility to study comparative material under their care. Comments by T. D. Cook (University of Alberta, Canada) and C. Duffin (Surrey, U.K.) greatly improved the manuscript. Financial support for this project is provided by the Austrian Science Fund (FWF, grant P26465-B25 to J.K.), the Swedish Research Council (VR grant 2009-4447 to T.M.), the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET grant PIP 0462 to M.R.), and the Argentinian National Agency for Promotion of Science and Technology (ANPCyT grant PICTO-2010-152 0093 to M.R.).