Description and Classification

Dilophosaurus was a medium-sized carnivorous dinosaur, estimated to have reached lengths of about 6 to 7 meters (20 to 23 feet) and weighed around 400 kilograms (880 pounds). It had a relatively slender and agile build, walking on two long legs (bipedal). Its most recognizable feature was the pair of delicate, bony crests on its skull, which ran parallel to each other from just behind the nostrils to above the eyes. These crests were too thin and fragile for combat and were likely used for display, perhaps to attract mates or identify members of its own species. The skull itself was somewhat long and narrow, with a noticeable notch or kink in the upper jaw, located behind the first row of teeth. Dilophosaurus had long arms with three-fingered hands equipped with sharp claws, useful for grasping prey. A long tail helped it maintain balance while moving.

In terms of classification, Dilophosaurus is a member of the Theropoda, the group of mostly meat-eating dinosaurs that also includes giants like Tyrannosaurus rex and birds. It is considered an early theropod. Its exact position within Theropoda has been debated, with some placing it within the Coelophysoidea (related to dinosaurs like Coelophysis), while others suggest it belongs to its own family, Dilophosauridae, or represents a more primitive form outside of more advanced theropod groups. It represents an important stage in theropod evolution after the Triassic period.

Distinguishing Features

• A prominent pair of thin, arched bony crests on the top of its skull.
• A distinct notch or kink in the upper jaw between the premaxillary and maxillary bones, creating a gap behind the front teeth.
• Relatively long neck and a slender, lightweight body compared to later large theropods.
• Long forelimbs for its body size, ending in three-fingered hands with sharp claws.

Paleoenvironment and Diet

Dilophosaurus lived in what is now the Kayenta Formation of Arizona, USA. During the Early Jurassic, this area was a floodplain environment with rivers, streams, and lakes, supporting a diverse array of plant and animal life. The climate was likely seasonal, with both wet and dry periods. Dilophosaurus shared this habitat with other dinosaurs, including the early sauropodomorph Sarahsaurus, the small armored dinosaur Scutellosaurus, and other early theropods. Pterosaurs flew overhead, and early crocodile relatives and small mammal-like reptiles were also present.

As a theropod, Dilophosaurus was a carnivore. The structure of its skull and teeth, particularly the notch in its upper jaw and somewhat delicate snout, suggests it may not have hunted very large or powerful prey. It likely fed on smaller dinosaurs, early mammals, lizards, and possibly fish. The kink in its jaw might have helped it secure struggling prey or process smaller food items. While sometimes depicted as a fish-eater due to this jaw feature, its primary diet is still under investigation.

Significance and Ongoing Research

Dilophosaurus is a significant dinosaur because it provides valuable information about the diversity and evolution of theropods during the Early Jurassic, a period of recovery and diversification after the Triassic-Jurassic extinction event. Its unique crests offer insights into dinosaur display structures and potential social behaviors, indicating that visual communication might have been important for these animals. Dilophosaurus gained widespread popular recognition through its appearance in the movie “Jurassic Park,” which depicted it with a neck frill and the ability to spit venom. However, there is no fossil evidence to support either of these features; they were fictional additions for the film.

Ongoing research on Dilophosaurus continues to refine our understanding of this dinosaur. Paleontologists study its anatomy in detail to better determine the function of its crests and its exact relationships to other theropods, such as Dracovenator from South Africa and Sinosaurus from China, which also had head crests. Further investigation into its paleoecology helps reconstruct its role as a predator within the Kayenta Formation ecosystem and how it interacted with other species. New fossil discoveries and analytical techniques continue to shed light on this fascinating early theropod.