Monotremes

Monotremes () are mammals of the order Monotremata. They are the only mammals still in existence which lay eggs, rather than bearing live young. The five extant monotreme species are the platypus and the four species of echidnas. Monotremes are typified by structural differences in their brains, jaws, digestive tracts, reproductive tracts, and other body parts, compared to the more common mammalian types. Although they are different from other living mammals in that they lay eggs, female monotremes are like other mammals in that they nurse their young with milk.

Echidnas (), sometimes known as spiny anteaters, are quill-covered monotremes (egg-laying mammals) belonging to the family Tachyglossidae , living in Australia and New Guinea. The four extant species of echidnas and the platypus are the only living mammals that lay eggs and the only surviving members of the order Monotremata. The diet of some species consists of ants and termites, but they are not closely related to the American true anteaters or to hedgehogs. Their young are called puggles.