It is significant that the whole type of their cloaca much resembles that of the Crocodilia and Chelonia, in opposition to that of the Lacertilia.
The first exponent of the theory of sudden appearance of new parts and new types, to our knowledge, was Geoffroy St Hilaire, who suggested saltatory evolution through the direct action of the environment on development, as explaining the abrupt transitions in the Mesozoic Crocodilia and the origin of the birds from the reptiles.
The Crocodilia form a separate order of reptiles with many peculiarities.
Within the glottis is a pair of membranous folds which serve as vocal cords; all the Crocodilia are possessed of a loud, bellowing voice.
All the Crocodilia possess two pairs of musk-glands in the skin; one is situated on the inner side of the lower jaw.