Monotreme

Monotremes Temporal range: Lower Cretaceous – Recent
Short-beaked echidna
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
(unranked):	Australosphenida
Order:	Monotremata C.L. Bonaparte, 1837
Families
†Kollikodontidae Ornithorhynchidae Tachyglossidae †Steropodontidae

Monotremes are a group of mammals that form the order Monotremata. Monotremes are the only mammals that lay eggs, but they also feed their babies with milk.

The word 'monotreme' refers to their common rear opening, the cloaca. In amphibia, reptiles, birds and probably all early tetrapods, there is a common opening for urine, reproduction and faeces.