Any phylogeneticists in the audience should read Madagascar Mammals Traced to African Ancestor. It summarizes a recent Nature paper:
Madagascar’s carnivorous mammals are descendants of a mongoose-like creature that floated to the island from Africa on a raft of vegetation about 21 million years ago, scientists said Wednesday.
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According to the research, carnivorous mammals are not old enough to have been present on Madagascar before the split with Africa, and if there was a land bridge other species probably would have crossed it too.
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“In fact, all 100 or so known species of terrestrial mammals native to Madagascar, which fall in four orders — carnivorans, lemurs, tenrecs and rodents — can now be explained by only four colonization events,” he said.