A continent lost?

Why are lemurs only found in Madagascar and not mainland Africa? Perhaps because they were always restricted to the island and never made it to the continental mainland?
When lemur fossils were found in the subcontinent, they spawned theories about existence of a greater continent over the present-day Indian Ocean that connected Madagascar, south India and Australia. These were confirmed by a drilling mission. This is understood to have significant implications to the commonality of origins for Dravidian and Aboriginal races. And a missing continent, of course..