Answer:
Monotremes are egg laying mammals (Prototheria) instead of mammals which give birth to live young like marsupials (Metatheria) and placental mammals (Eutheria). They are still classified as mammals because they feed their young on mothers' milk.
Australia has two species of monotremes: the platypus and the short-beaked echidna.
The long-beaked echidna is the only other species of monotreme, and lives in New Guinea, as does a smaller population of short-beaked echidna.
The name monotreme is derived from two Greek words meaning "one-holed", because they have just one external opening, the cloaca, for both waste elimination and for reproduction. The cloaca leads to the urinary, faecal and reproductive tracks, all of which join internally, and it is the orifice by which the female monotreme lays her eggs.
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