Dilophosaurus. Computer artwork of an adult male Dilophosaurus dinosaur on a hilltop covered in sago palms, Williamsonia gigas, and ferns. The tree-like Williamsonia gigas was a seed plant that existed for 130 million years before becoming extinct. The other plants illustrated here exist to this day. Dilophosaurus was a carnivorous theropod dinosaur that lived during the Early Jurassic Period (approx 200-176 million years ago).