Revision of Eocene Antarctic carpet sharks (Elasmobranchii, Orectolobiformes) from Seymour Island, Antarctic Peninsula

Abstract

Seymour Island, Antarctic Peninsula, was once called the ‘Rosetta Stone’ of Southern Hemisphere palaeobiology, because this small island provides the most complete and richly fossiliferous Palaeogene sequence in Antarctica. Among fossil marine vertebrate remains, chondrichthyans seemingly were dominant elements in the Eocene Antarctic fish fauna. The fossiliferous sediments on Seymour Island are from the La Meseta Formation, which was originally divided into seven stratigraphical levels, TELMs 1–7 (acronym for Tertiary Eocene La Meseta) ranging from the upper Ypresian (early Eocene) to the late Priabonian (late Eocene). Bulk sampling of unconsolidated sediments from TELMs 5 and 6, which are Ypresian (early Eocene) and Lutetian (middle Eocene) in age, respectively, yielded very rich and diverse chondrichthyan assemblages including over 40 teeth of carpet sharks representing two new taxa, Notoramphoscyllium woodwardi gen. et sp. nov. and Ceolometlaouia pannucae gen. et sp. nov. Two additional teeth from TELM 5 represent two different taxa that cannot be assigned to any specific taxon and thus are left in open nomenclature. The new material not only increases the diversity of Eocene Antarctic selachian faunas but also allows two previous orectolobiform records to be re-evaluated. Accordingly, Stegostoma cf. faciatum is synonymized with Notoramphoscyllium woodwardi gen. et sp. nov., whereas Pseudoginglymostoma cf. brevicaudatum represents a nomen dubium. The two new taxa, and probably the additional two unidentified taxa, are interpreted as permanent residents, which most likely were endemic to Antarctic waters during the Eocene and adapted to shallow and estuarine environments.

http://zoobank.org/urn:lsid:zoobank.org:pub:DD064382-3802-41A9-9B89-3095A6533B8A

Keywords:

• Chondrichthyes
• Hemiscyllidae
• Orectolobidae
• La Meseta Formation
• Southern Ocean
• Palaeogene

Acknowledgements

The Argentinian Antarctic Institute (IAA-DNA), Argentinian Air Force and Swedish Polar Research Secretariat (SPFS) are acknowledged for logistic support for fieldwork on Seymour Island. The authors are grateful to Martin de los Reyes, Museo de La Plata, for picking the small fractions in the laboratory. The authors would like to thank Patricia Holroyd, Museum of Paleontology, University of California, Berkeley, for access to the Woodburne collection of La Meseta specimens and for the possibility to study comparative material. Financial support for this project is provided by The Austrian Science Fund (FWF: P26465-B25 to JK), Swedish Research Council (VR grant 2009-4447 to TM), the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET grant PIP 0462 to MR), and the Argentinian National Agency for Promotion of Science and Technology (ANPCyT grant PICTO 0093/2010 to MR). We also want to thank C. Underwood and G. Case for their constructive reviews, and the Associate Editor Z. Johanson for all her support and suggestions that greatly improved the manuscript.

Additional information

Funding

The Austrian Science Fund (FWF: P26465-B25 to JK), Swedish Research Council (VR grant 2009-4447 to TM), the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET grant PIP 0462 to MR), and the Argentinian National Agency for Promotion of Science and Technology (ANPCyT grant PICTO 0093/2010 to MR).