New Record of Selachian (shark) fauna from the early Miocene (Aquitanian) of Kachchh Region (western India): Palaeoecological and Palaeobiogeographic significance

The past two decades have witnessed a renewed interest in the Neogene (mainly Miocene) interval of the Kachchh (= Kutch) region owing to its potential to yield numerous records on fishes, reptiles, birds, and marine and terrestrial mammals. However, the Piscean (mainly selachian) faunal records from the Neogene (Miocene) interval have been sparsely emphasized. The current investigation reveals the most diverse assemblage of selachian (shark) fauna, to date, from the Aquitanian (~ 21 Ma) Khari Nadi Formation at Kotada, Kutch Basin, western India. The recovered selachian (shark) fauna comprises five genera, including Galeocerdo , Physogaleus , Carcharhinus , Negaprion and Hemipristis representing seven species. The presence of Galeocerdo mayumbensis , Carcharhinus falsiformis , and C. brevirostris comprise the oldest Neogene records from the Kutch Basin, western India. The diversity similarity coefficient data suggests that the Aquitanian selachian assemblage is quite dissimilar compared to the previously known Langhian-Serravallian assemblage from the Kutch Basin, western India. Global distribution of the selachian fauna reveals intermittent biogeographic connectivity between the Atlantic, the Mediterranean, and the Indian Oceanic realms during the Aquitanian to Tortonian. However, complete stratigraphic records across various Oceanic realms are warranted to fully understand the diversity change(s) and the direction(s) of migration(s) of the selachian fauna. Considering the data on Modern relatives of the recovered selachian fauna, it is most likely that the recorded selachian fauna dwelled in warm-temperate to tropical shallow coastal waters in the Neritic to Intertidal zones, i.e., coastal-reef to mesopelagic environment(s).