Noun
any member of the Amniota
Source: WordNetDescription Size comparison of male S. punctatus and human The tuatara is considered the most unspecialised living amniote ; the brain and mode of locomotion resemble those of amphibians and the heart is more primitive than that of any other reptile. Source: Internet
Environmental sex determination preceded the genetically determined systems of birds and mammals; it is thought that a temperature-dependent amniote was the common ancestor of amniotes with sex chromosomes. Source: Internet