‖n. pl. [ NL. ] (Zool.) The division of Vertebrata in which the embryo develops an allantois. It includes reptiles, birds, and mammals. [ 1913 Webster ]
‖n. pl. [ Gr. 'an priv. + E. allantoidea. ] (Zool.) The division of Vertebrata in which no allantois is developed. It includes amphibians, fishes, and lower forms. [ 1913 Webster ]