In the less well known early Jurassic of North. America, there were other important developments, in terms of dinosaurian evolution. One such example is the first well known large theropod, Dilophosaurus wetherilli. Dilophosaurus is found in Arizona, and possibly other places in the American southwest, and is a fairly usual early theropod, save for two things; its large size, and its odd-looking crests on its head. Its large size was probably an adaptation to increasing prey size, as prosauropods, theryophorans, and ornithopods, as well as potentially true sauropods, are known from the ground where Dilophosaurus is from.
A retreating Dilophosaurus bellows a call at a rival across the river. Also in this picture are three "Syntarsus" kayentakatae, a lizard, a crocodile-like reptile, and several bones. The Kayenta Formation, where Dilophosaurus has been found, was dominated by large, shallow streams with stands of trees around their edges, and large dune fields.
Infant Mortality. An adult Dilophosaurus guards her child as it prepares to eat a Scutelosaurus chick. Infant mortality was probably high in the Jurassic, much as it is today, and probably provided a convenient source of food for local carnivores.
A male Dilophosaurus sniffs a dead Kayentatherium, deciding if it is safe to eat or not. While Dilophosaurus was likely an active hunter, it no doubt would have eaten anything dead that it happened across as well This image was done at the behest of ReBecca Hunt, for her use on he website.
Head profile of the early Jurassic predator Dilophosaurus wetherilli.
to the Jurassic.