It was a theropod (a meat-eating dinosaur) about 20 feet (6 m) long, about 5 feet (1.5 m) tall at the hip, and weighing about 650 to 1,000 pounds (300 kg to 450 kg). It had two thin, bony, almost semi-circular crests on its head; these may have been for mating displays. It had short arms with three-fingered hands and strong legs with four-toed feet (one toe was a dewclaw ). Both fingers and toes had claws. It had hollow bones and an S-shaped, curved neck.Dilophosaurus lived about 201 to 189 million years ago, during the early Jurassic period. Among its contemporaries in North America during this time, all smaller than Dilophosaurus, were: the meat-eaters Coelophysis (about 10 feet long), Syntarsus, and Segisaurus ,the omnivores Massopondylus and Anchisaurus,the plant-eaters Scutellosaurus and Ammosaurus.
Dilophosaurus may have roved in packs, since three specimens were found together in Arizona, USA.Dilophosaurus was a carnivore, a meat eater. It had loosely attached jaws which would have made killing animals with its teeth difficult. It must have killed with its clawed arms and legs, and/or scavenged carcasses.Dilophosaurus walked on two muscular legs and was a relatively fast runner, leaving bird-like footprints on land. Some of its fossilized footprints are only impressions of the claw-tips. This indicates that Dilophosaurus may have been walking in water at the time. Dilophosaurus' leg length was about about 1.65 m; it's stride length (distance between footprints) was about 2.13 m.The first fossil Dilophosaurus skeleton was found in Arizona, USA, in the 1940's. Dilophosaurus was named in 1970 by Samuel P. Welles. There have been three Dilophosaurus fossils found in the USA, all found together in Arizona. They are now at the University of California's Museum of Paleontology at Berkeley, USA. Another specimen may have been found in China.