Dilophosaurus is a genus of theropod dinosaurs that lived in North America during the Early Jurassic period, around 193 million years ago. These creatures were discovered in northern Arizona in 1940 and were classified as a new species in the Megalosaurus genus, named M. wetherilli in honor of S. P. Welles in 1954. The name of the genus means "two-crested lizard." Since then, other specimens have been found, including a juvenile.

Dilophosaurus was roughly 7 meters long and weighed around 400 kg. It was one of the first large predatory dinosaurs and was the largest known terrestrial animal in North America at that time. It had a relatively slender and lightweight build, with a large skull that was proportionally thin. The snout was narrow, and the upper jaw had a notch below the nostrils. The teeth were long, curved, and thin. The neck was long, the arms were powerful and had four fingers, three with large claws, and a fourth being rudimentary. The femur bone was enormous, the legs were sturdy, and the toes had large claws. Dilophosaurus was bipedal and agile, allowing it to hunt large animals. It could also feed on smaller animals and fish.