Crocodylomorpha is a group of archosaurs that includes the crocodilians and their extinct relatives.During Mesozoic and early Cenozoic times, Crocodylomorpha was far more diverse than it is now. Triassic forms were small, lightly built, active terrestrial animals. These were supplanted during the early Jurassic by various aquatic and marine forms. The Later Jurassic, Cretaceous, and Cenozoic saw a wide diversity of terrestrial and semi-aquatic lineages.