Mammals are reptiles.
Mammals are any vertebrates within the class Mammalia ( [ məˈmeɪli.ə ] from Latin mamma #Latin `` breast '' ) , a clade of endothermic amniotes distinguished from reptiles ( including birds ) by the possession of a neocortex ( a region of the brain ) , hair , three middle ear bones and mammary glands . Reptiles are tetrapod ( four-limbed vertebrate ) animals in the class Reptilia , comprising today 's turtles , crocodilians , snakes , amphisbaenians , lizards , tuatara , and their extinct relatives .