Kayenta formation fauna, illustration. At centre is a Kayentatherium cynodont carrying its young in its mouth. Cynodonts included the animals that later evolved into mammals. In the foreground is a kayentachelys turtle. In the background are Dilophosaurus dinosaurs. These animals were all lived on what is now the Colorado Plateau of the USA in the Early Jurassic (196-183 million years ago), a geologic layer known as the Kayenta formation.