the GNU version of the Collaborative International Dictionary of English
noun plural.
That group of vertebrates which develops in its embryonic life the envelope called the amnion. It comprises the reptiles, the birds, and the mammals.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
noun.
higher vertebrates (reptiles, birds and mammals) possessing an amnion during development
Word Usage
"Finally, the fetal membranes and their relations to the fetus and uterus are studied in their variations among the amniota."