Comments on early saurischians

On the basis of reptilian remains from the Triassic of Argentina (Ischigualasto and Los Colorados formations), and the comparisons made in English and U.S. museums, the author discusses the classification of early saurischians and assumes that the differences between early camosaurs and prosauropods may be of a degree not higher than that between early coelurosaurs and camosaurs. It is argued that Ornithosuckus is more likely to be a pseudosuchian than a primitive carnosaur; and that the origin of the two orders of dinosaurs very probably occurred well before the Upper Triassic. During the Upper Triassic the dinosaurs competed with and displaced the pseudosuchians, probably all over the world.