The discovery of the egg-laying monotremes platypus and echidna in Australia more
than 200 years ago caused great excitement and controversy in the zoological world.
Their combination of reptilian, mammalian and unique characteristics seemed
incongruous to 19th century scientists; and because of its strange and unique amalgam
of characters, the platypus was initially thought to be a skilled taxidermist’s hoax.
However, monotremes were immediately identified as mammals because they bear
fur and feed their young with milk. The evolutionary status of monotremes, either at
the root of mammals or as offshoot of the marsupial lineage, remains controversial
today although most monotreme biologists agree that the Prototherians (the
monotremes) diverged before the Therian (marsupial and eutherian) mammals.