Monotremes are a group of primitive mammals found only in Australia and New Guinea. The three species of monotremes are:
* Platypus: This is the most well-known monotreme, with its duck-like bill and webbed feet.
* Echidnas: There are four species of echidnas, all of which have spines and long snouts.
Monotremes lay leathery eggs that they incubate in a pouch, much like marsupials. However, unlike marsupials, monotreme young are born in a relatively undeveloped state and rely on their mother's milk for nourishment.