Here are some key characteristics of monotremes:
* Lay eggs: Unlike other mammals, they don't give birth to live young.
* Primitive traits: They have features that resemble reptiles, such as a cloaca (a single opening for waste and reproduction) and a pouch where they incubate their eggs.
* Echidnas and platypuses: The only surviving monotremes are echidnas and platypuses, both found only in Australia and New Guinea.
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