|A selection of preserved caimans|
Crocodyliformes, including a distant early ancestor of modern members of Crocodylia, arose some 220 mya. Crocodylia arose in the Late Cretaceous and include 23 extant members of the superfamilies: Crocodyloidea (Crocodiles), Alligatoroidea (Caimans and Alligators), and Gavialoidea. Debate still exists on their exact phylogenetic relationships due to apparent differences in molecular and morphological trees. Members of the previously mentioned superfamilies can generally be distinguished based on skull anatomy. Regardless, all members of Crocodylia are derived Archosauromorphs and therefore exhibit the diapsid skull condition - as demonstrated below, snout morphology can also vary a great deal as well between members of Crocodylia.
caudal vertebrae, sacral vertebrae, lumbar vertebrae, thoracic vertebrae, and cervical vertebrae)
Pictured to the right are the bones of the pectoral girdle: the interclavicle, the scapula, the procoracoid, and the sternum (not seen - connects the procoracoids)
Pictured below are the bones of the pelvic girdle: the ilium, the ischium, and the pubis, as well as: the sacral vertebrae (where the ilium attaches) and the ungual phalanx (the the claw bearing phalanges)
|Caiman cloaca and "penis"|