Zoology. A vertebrate characterized by the presence during development of the allantois, or of fetal membranes generally; an amniote. Now disused.

With pl. concord. The vertebrates, comprising reptiles, birds and mammals, which possess in embryonic life an allantois and an amnion.

Any vertebrate whose embryo develops within an amnion and chorion and possesses an allantois, i.e. a reptile, bird, or mammal; cf. amniota, n.