Were there size constraints on biotic exchanges during the Northward drift of the Indian plate?

Abstract

Contrary to the geophysical data, which envisaged a long period (about 100 Ma) of physical isolation for the Indian subcontinent during its northward journey, the palaeontological data from the Upper Cretaceous continental sequences (Deccan infra- and inter-trappean) of peninsular India unequivocally demonstrate the nonendemic nature of the biota with close biogeographics links to the southern as well as northen hemisphere continents. The Myobatrachinae frogs, pelomedusid turtles, titanosaurid and abelisaurid dinosaurs, and Sudamericidae mammals exhibit distinct Gondwanan relationships. In marked contrast, the pelobatid and discoglossid frogs, anguid lizards, alligatorid crocodiles, palaeoryctid mammals, ostracodes, and charophytes indicate Laurasian connection. The Gondwanan taxa have been considered as representing an immigration event before 80 Ma (time of separation of Madagascar from India) and possibly between 85-90 Ma that facilitated the exchange of fauna between South America and Indo-Madagascar via Antarctica and Kerguelen Plateau. As far as the Laurasian connection is concerned, it has been shown that the size of organisms had a significant control on the biotic exchanges between the Indian subcontinent and the Laurasian landmasses. Only small-sized taxa could participate in the northern biotic interchanges through filter corridor/sweepstake mode of dispersal involving the Trans-Himalayan Arc, Kohistan-Dras island arc copmlex and some oceanic islands which have been destroyed in due course of time at the subduction zone south of the Asian mainland/Trans-Himalayan Arc.