Fossil snakes from the Eocene of India: new material with comments on phylogenetic relations and biogeographic and paleoecological implications

Abstract Eocene snakes of India have the potential to shed light on the nature of snake diversification on the subcontinent following the Deccan volcanism at the Cretaceous-Paleogene boundary (K-Pg), when India was still a northward-drifting isolated landmass prior to its collision with Asia. Here, we report a diverse snake fauna from the Eocene of Kutch, western India. The fauna, dominated by aquatic forms, includes palaeophiids, a giant madtsoiid, and a possible nigerophiid. The palaeophiids from the middle Eocene (late Lutetian) comprise ? Palaeophis Owen, 1841 and Pterosphenus rannensis n. sp. Together, these taxa enrich the record of fossil snakes in the poorly known late Lutetian of India and represent the youngest record of Palaeophiidae from the Indian subcontinent. Pterosphenus rannensis n. sp. shows intermediate morphology between Palaeophis and Pterosphenus -grade snakes and is phylogenetically the earliest-diverging member of Pterosphenus Lucas, 1898. Additionally, the middle Eocene Pterosphenus biswasi Rage et al., 2003 is reassessed and retained as a valid taxon based on pterapophyseal morphology and overall form. Biogeographic considerations highlight the importance of the Indian fossil record in understanding the origin and diversification of the genus Pterosphenus. The prevalence of niche partitioning is suggested for the palaeophiids, with Pterosphenus rannensis n. sp. recovered from a tidal setting and ? Palaeophis sp. indet. from a marsh/swamp setting. The new Indian madtsoiid from the middle Eocene (early Lutetian) represents a sympatric taxon with the terrestrial/semiaquatic giant Vasuki indicus Datta and Bajpai, 2024 coexisting in a back-swamp marsh setting. The early Eocene (Ypresian) nigerophiid is among the oldest Cenozoic occurrences of this family globally. UUID: http://zoobank.org/dc529074-73a6-4869-9b49-44caf9e2d956