Why are no eutherians indigenous to australia?
1 Answer
Continental drift led to early geographic isolation of Australia almost 100 million years ago: when only prototherian and metatherian mammals roamed the earth. No eutheria ever evolved in the continent.
Explanation:
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Evolutionary history of marsupial mammals in the form of fossils is not consistent, but fossils of such early mammals from mesozoic era are excavated from most parts of the world.
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Australia separated from erstwhile southern landmass of Gondwana with very early types of prototherian and metatherian (=marsupial) mammals.

- Only two eutherian mammals could eventually reach Australian continent later by migrating from nearby land masses: these were the rats and bats!