Amnion (Gr. amnion, membrane around the fetus).
The innermost of the extraembryonic membranes forming a fluid
filled sac around the embryo in amniotes.
Amniote
Having an amnion; as a noun, an animal that develops an amnion in
embryonic life, that is, reptiles, birds, and mammals.
Analogy
Similarity of function but not of origin.
Cladogram
A branching diagram showing the pattern of sharing of
evolutionarily derived characters among species or higher taxa.
Coelom
The body cavity in triploblastic animals, lined with mesodermal
peritoneum