Informal name for extant, synapsid amniotes.

There are three basic types of mammals. These are they eutherians – all of which today are also placental mammals – along with the marsupials and monotremes. It is the monotremes whcih are oviparous and which also lack nipples.

Mammals possess , produce milk (), have , display that consist of a single , possess a variety of mammal-specific , and use to pump their . Most mammals also their live (they are viviparous) and also possess which supply milk to their young.

Mammals are members of class Mammalia.