New record of selachian (shark) fauna from the early Miocene (Aquitanian) of Kachchh region (western India): palaeoecological and palaeobiogeographic significance

Our investigation reveals a diverse assemblage of selachian (shark) fauna from the Aquitanian Khari Nadi Formation, Kachchh region, western India. The recovered selachian fauna comprises five genera that include: Galeocerdo, Physogaleus, Carcharhinus, Negaprion and Hemipristis, representing six species. Galeocerdo mayumbensis, Carcharhinus falciformis, and Negaprion eurybathrodon (present investigation) are the oldest Neogene records from western India. The calculated diversity similarity coefficient indices for selachian fauna hint at biotic turnover in western India across the Aquitanian-Langhian interval. The global distribution of the selachian genera Galeocerdo, Physogaleus, Carcharhinus, Negaprion, and Hemipristis suggests biotic connections across the Atlantic, Mediterranean, and Indian Ocean realms during the Aquitanian. However, biotic connections between the west coast of India were intermittently restricted from the Mediterranean during the Langhian-Tortonian. The recorded shark teeth and their geochemical analyses (carbonate δ13C and δ18O) allow us to infer that the fauna dwelled in a warm temperate to tropical Neritic to Intertidal, i.e. coastal-reef to mesopelagic palaeoenvironments, quite likely consuming invertebrates and fish fauna. Nonetheless, additional fossil records are warranted across the Tethys-NeoTethys Oceanic realms to comprehend the direction(s) of migration(s) of selachian fauna and to understand the change in selachian diversity in view of the global climatic and geological events during the Miocene.