 It was not until the beginning of the 19th century that it became clear that reptiles and amphibians are, in fact, quite different animals, and Pierre André Latreille erected the class "Batracia" (1825) for the latter, dividing the tetrapods into the four familiar classes of reptiles, amphibians, birds, and mammals.The British anatomist Thomas Henry Huxley made Latreille's definition popular and, together with Richard Owen, expanded Reptilia to include the various fossil "antediluvian monsters", including dinosaurs and the mammal-like (synapsid) "Dicynodon" he helped describe.This was not the only possible classification scheme