Order of the ‘ruling reptiles’ (Archosauria) which includes the crocodiles, alligators, caimans, and gavials (gharials). They are derived from thecodontian ancestors and are closely related to the dinosaurs and pterosaurs. They are first recorded from Triassic rocks and were the only archosaurs to survive the Mesozoic era, although strictly speaking the birds (Aves) are also archosaurs.