Many Indian species have descended from those of Gondwana, the southern supercontinent from which India separated more than 100 million years ago.{{sfn|Crame|Owen|2002|p = 142}} India's subsequent collision with Eurasia set off a mass exchange of species. However, volcanism and climatic changes later caused the extinction of many endemic Indian forms.{{sfn|Karanth|2006}} Still later, mammals entered India from Asia through two zoogeographical passes flanking the Himalayas.{{sfn|Tritsch|2001}} This had the effect of lowering endemism among India's mammals, which stands at 12.6%, contrasting with 45.8% among reptiles and 55.8% among amphibians.{{sfn|Puri}} Notable endemics are the vulnerable hooded leaf monkey and the threatened Beddom's toad of the Western Ghats.