Late Cretaceous-Early Palaeocene Lepisosteiform and Siluriform fish remains from Central India: palaeoecological, palaeoenvironmental and palaeobiogeographical implications

Abstract

Late Cretaceous-Early Palaeocene geo-climatic events played an important role in the diversification of the modern ichthyofauna. Lepisosteiformes and Siluriformes are two diverse clades of freshwater fishes, poorly known from India in this time interval. Their fossil record documents their early diversification and can be used to reconstruct palaeobiogeographic relationships among the continental masses during the Late Mesozoic. Indeed, the Cretaceous-Palaeocene is an exceptional time span for the Indian plate as it underwent a primary spatial reorganisation and remarkable geologic and climatic changes with extensive outpouring of the Deccan basaltic magma. Field investigation in a Deccan sedimentary sequence at Kisalpuri, Central India has yielded new, rich, and taxonomically important fossil material of Lepisosteiformes (Lepisosteus indicus, Lepisosteidae) and Siluriformes (Siluriformes indet.), which significantly improves their Cretaceous-Palaeocene fossil record from the Indian subcontinent. These fish lived in freshwater environments such as large rivers, lakes, and coastal areas. Their presence along with other aquatic biotic elements suggests that the Kisalpuri was an abundant aquatic ecosystem rich in nutrients, which attracted a diverse range of organisms to live together with fish. Biostratigraphically, these fishes first emerged in the Late Cretaceous-Early Palaeocene on the Indian subcontinent, and later, they spread to other parts of subcontinent throughout the Cenozoic. Their earliest intra-continental distribution was controlled by the palaeodrainage network influenced by the volcanic flows of the Deccan traps. Their inter-continental palaeobiogeographic distribution was broadly controlled by the sequential break-up of Pangaea. There appear to be close palaeobiogeographic linkages between South America and India during the Cretaceous-Palaeocene era based on the similarity between the Lepisosteiformes and Siluriformes remnants from India and those reported from the Upper Cretaceous of the Bauru Group, Brazil.