what was its diet?
Different views suggest that they depended on large and small preys and fish.
Dilophosaurus
premaxillary teeth for plucking and tearing rather than biting, and the maxillary teeth further back for piercing and slicing. He thought that it was probably a scavenger rather than a predator, and that if it did kill large animals, it would have done so with its hands and feet rather than its jaws. Welles did not find evidence of cranial kinesis in the skull of "Dilophosaurus", a feature that allows individual bones of the skull to move in relation to each other. In 1986, the paleontologist Robert T. Bakker instead found "Dilophosaurus", with its massive neck and skull and large upper teeth, to have been adapted for killing large prey, and strong enough to attack any Early Jurassic herbivores. In 1988, Paul dismissed the idea that "Dilophosaurus" was a scavenger, and claimed that strictly scavenging terrestrial animals are a myth. He stated that the snout of "Dilophosaurus" was better braced than had been thought previously, and that the very large, slender maxillary teeth were more 
what is dilophosaurus? A genus of theropod dinosaur. when was it discovered? In 1940.
wiki:1878777
Dilophosaurus [SEP] Feeding and diet
Welles found that "Dilophosaurus" did not have a powerful bite, due to weakness caused by the subnarial gap. He thought that it used its front premaxillary teeth for plucking and tearing rather than biting, and the maxillary teeth further back for piercing and slicing. He thought that it was probably a scavenger rather than a predator, and that if it did kill large animals, it would have done so with its hands and feet rather than its jaws. Welles did not find evidence of cranial kinesis in the skull of "Dilophosaurus", a feature that allows individual bones of the skull to move in relation to each other.