Elasmobranchs from the Lower Eocene Kalinino Formation of the Alai River, Saratov Region of Russia

ABSTRACT

A new elasmobranch assemblage including 14 shark taxa, mainly lamniformes (9 taxa), is described from the Lower Eocene (NP 10–11) Kalinino Formation of the Alai River Basin, Baltai District, Saratov Region of Russia. The Nikulinka elasmobranch assemblage may have characterised inner neritic environments of the eastern part of the sub-boreal European paleobiogeographic region, being closely related to assemblages from the south-most sector of the boreal Western Siberian Province (southern Trans-Urals and Turgay straight). The absence of myliobatids in Nikulinka and Trans-Uralian localities may have been caused by the influence of Arctic water masses through meridional straits in early Ypresian. This is the first chondrichthyan assemblage from the Palaeogene of the Middle Volga Region, European Russia.

KEYWORDS:

• Chondrichthyes
• Elasmobranchii
• Eocene
• biostratigraphy
• palaeobiogeography

Acknowledgments

We indebted to the late Dmitry S. Khydyakov (1928–2020), a famous Saratov local historian for sharing with us data about the Nikulinka locality. We thank Dr Vladimir B. Seltzer (SSU) and the former ‘young geologist’ Alexander V. Lapkin (Saratov) for providing sharks’ teeth from the locality collected in 1996. We thank David Ward (NHMUK, London) for critical reading of the manuscript and correcting the English. Finally, J. Pollerspöck and the “Shark-references” web-project (Pollerspöck and Straube 2022) are thanked for permanent access to rare chondrichthyan publications. We wish to thank G. Dyke (Editor) and three anonymous reviewers for the reviews that improved the quality of this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The research received support from the Russian Science Foundation, grant 22-27-00134, https://rscf.ru/en/project/22-27-00134/;