Crocodilia is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 94 million years ago in the Late Cretaceous period.The order Crocodilia includes the true crocodiles,the alligators and caimans, and the gharial and false gharial . Although the term 'crocodiles' is sometimes used to refer to all of these, crocodilians is a less ambiguous vernacular term for members of this group.