During the Lower Jurassic , dinosaurs such as Dilophosaurus , Anchisaurus , Ammosaurus , Syntarsus , and the early thyreophoran Scutellosaurus lived in North America . During the Early Jurassic Period , dinosaurs such as Dilophosaurus , Anchisaurus , Ammosaurus , Syntarsus , and the early thyreophoran Scutellosaurus lived in North America .