Dilophosaurus

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Lore & Background

At about 7 m in length, with a weight of about 400 kg, Dilophosaurus was one of the earliest large predatory dinosaurs and the largest known land-animal in North America at the time. It was slender and lightly built, and the skull was proportionally large, but delicate. The snout was narrow, and the upper jaw had a gap or kink below the nostril. It had a pair of longitudinal, arched crests on its skull; their complete shape is unknown, but they were probably enlarged by keratin. The mandible was slender and delicate at the front, but deep at the back. The teeth were long, curved, thin, and compressed sideways. Those in the lower jaw were much smaller than those of the upper jaw. Most of the teeth had serrations at their front and back edges. The neck was long, and its vertebrae were hollow, and very light. The arms were powerful, with a long and slender upper arm bone. The hands had four fingers; the first was short but strong and bore a large claw, the two following fingers were longer and slenderer with smaller claws; the fourth was vestigial. The thigh bone was massive, the feet were stout, and the toes bore large claws. Dilophosaurus has been considered a member of the family Dilophosauridae along with Dracovenator, a group placed between the Coelophysidae and later theropods, but some researchers have not found support for this grouping. Dilophosaurus would have been active and bipedal, and may have hunted large animals; it could also have fed on smaller animals and fish. Due to the limited range of movement and shortness of the forelimbs, the mouth may instead have made first contact with prey. The function of the crests is unknown; they were too weak for battle, but may have been used in visual display, such as species recognition and sexual selection. It may have grown rapidly, attaining a growth rate of 30 to 35 kg per year early in life. The holotype specimen had multiple paleopathologies, including healed injuries and signs of a developmental anomaly. Dilophosaurus is known from the Kayenta Formation, and lived alongside dinosaurs such as Scutellosaurus and Sarahsaurus. It was designated as the state dinosaur of Connecticut based on tracks found there. Dilophosaurus was featured in the novel Jurassic Park and its movie adaptation, where it was given the fictional abilities to spit venom and expand a neck frill, and was depicted as smaller than the

Reader's Guide

Dilophosaurus was a bipedal, active predator, one of the earliest large theropods and the biggest land animal in North America during the Early Jurassic. It reached about seven meters in length and weighed roughly four hundred kilograms, with a slender, lightly built frame and a proportionally large but delicate skull. The snout was narrow, and the upper jaw featured a gap or kink below the nostril. Its most distinctive feature was a pair of longitudinal, arched crests on the skull, which were probably enlarged by keratin but too weak for combat; they may have served for visual display, such as species recognition or sexual selection. The teeth were long, curved, thin, and compressed sideways, with serrations on both edges; teeth in the lower jaw were much smaller than those in the upper. The neck was long, with hollow, very light vertebrae. The arms were powerful, with a long, slender upper arm bone, and the hands had four fingers: a short, strong first finger bearing a large claw, two longer, slenderer fingers with smaller claws, and a vestigial fourth finger. The thigh bone was massive, the feet stout, and the toes bore large claws. Because the forelimbs were short and had limited range of movement, the mouth likely made first contact with prey. It may have hunted large animals but could also have fed on smaller animals and fish. Growth was rapid early in life, with an estimated rate of thirty to thirty-five kilograms per year. The holotype specimen shows multiple healed injuries and signs of a developmental anomaly. Dilophosaurus is known from the Kayenta Formation, where it lived alongside dinosaurs such as Scutellosaurus and Sarahsaurus. Footprints attributed to it include resting traces. It was designated the state dinosaur of Connecticut based on tracks found there. The species was featured in the novel *Jurassic Park* and its film adaptation, which inaccurately depicted it as smaller, able to spit venom, and possessing a neck frill.

Did You Know?

• The specific name honors John Wetherill, a Navajo councilor and explorer, not an amateur archeologist.
• Samuel P. Welles assigned the species to the new genus Dilophosaurus in 1970 after realizing it bore crests on its skull.
• Dilophosaurus was one of the earliest large predatory dinosaurs and the largest known land-animal in North America at the time.

Common Misconceptions (Editorial)

People often think Dilophosaurus was small and able to spit venom or expand a neck frill, as depicted in popular films, but the facts confirm it was a large predator about 7 meters long, and there is no evidence in the provided record for venom or a frill. Another misconception is that Dilophosaurus had only two fingers on each hand; the record states its hands had four fingers, the first bearing a large claw.

Why It Matters (Editorial)

Dilophosaurus endures as a key figure in understanding early dinosaur evolution, representing one of the first large predatory dinosaurs to dominate North America. Its distinctive double crests and surprisingly lightweight, hollow neck vertebrae also make it a fascinating example of how specialized features evolved long before the more famous apex predators of the Jurassic and Cretaceous.