this class represents the embryonic form of the cloaca, as found in both mammals and non-mammals.

Endoderm-lined chamber that develops as pouch-like dilation of the caudal end of the hindgut and receives the allantois ventrally and two mesonephric ducts laterally; caudally it ends blindly at the cloacal membrane formed by the union of proctodeal (anal pit) ectoderm and cloacal endoderm, with no intervening mesoderm[MP].

uberon

cloaca

UBERON:0000163

http://purl.obolibrary.org/obo/uberon.owl, http://purl.obolibrary.org/obo/cl.owl

• cloacal membrane
• primitive urogenital sinus

• cloacal membrane
• primitive urogenital sinus