Mammal n. : One of the Mammalia.

Example:
What was the only Mammal to survive the early triassic period?

Taxonomy
mammals, Clade, mammalian, Infraclass, monotremes, marsupials, bones, placentals, therapsids, limbs, placental mammals, synapsids, lung, reptiles, fossils, mammal species, animals, Subclass.

Defination from the web:
mammal species give birth to live young. ... Living mammal species can be identified by the presence of sweat glands, including those that are specialized to produce milk. ...