This fast-moving killer with two large head crests would have sent peaceful, plant-eating dinosaurs scattering in terror as it galloped toward them . Dilophosaurus was slender , agile, and built for speed. It could have easily out run most dinosaurs that shared it's world and, armed with sharp - clawed hands and feet, it was capable of tearing through it's victims soft flesh with ease. Scientists are not sure why Dilophosaurus had the curious pair of bony crests on top of it's head. They were far too fragile to be used by male's when courting females or in warning displays to intimidate rivals.