IISER MOHALI

Abstract: India has a unique geological history that began as part of the Gondwana supercontinent, followed by rifting and an interval of rapid northward drift to its current position within Asia. During this rift-drift phase that spans about 60-70 million years, the Indian plate passed across different latitudinal belts and associated climatic zones. Such a dynamic geological history naturally prompts the question: How did the living organisms on the Indian plate respond to these dramatic tectonic and environmental shifts? Clues to this question lie in the Mesozoic (250-66 million years) fossil record of India. The fossils from the Triassic and Jurassic periods reveal that most Gondwanan taxa became extinct, with their remains subsequently buried and preserved during the plate’s northward journey, akin to the dead carried by Viking Funeral Ships. In the Cretaceous, when India was drifting very rapidly (15-20 cm/year) as an island, many taxa of Gondwanan origin boarded the Indian plate, which acted as a biotic ferry for its native Gondwanan species to colonize Asia and also fostered endemism. During this phase, the Indian plate served as the biological Noah’s Ark, carrying unique southern biotic elements across vast distances to Asia and vice versa. During its peak isolation from other landmasses, certain endemic taxa evolved in India, and subsequently, when some favorable dispersal modes were available, they migrated out of India. The arrival of some Northern Hemisphere taxa in India before the complete closure of the Tethys Sea also highlights the complexity of biotic dispersals, before the establishment of permanent land connections between India and Asia. These evolutionary and biogeographic dynamics will be explored in the context of India’s tectonic break-up, drift history and eventual collision with Asia.