“It has been independently lost or reduced in several amniote lineages, however, including crocodilians, birds, tuataras, iguanian lizards, cetaceans, and catarrhine primates.”
“Since amniote intromittent organs are hydrostatic, it follows that the wall of their erectile structures must be reinforced with inextensible fibers to prevent aneurysms.”
“They were the first vertebrates to lay an amniote egg, a new kind of incubator with a hard shell and a number of embryonic membranes.”