Discovery
The first recovery of Dilophosaurus skeletons occured when the University of California dispatched a fossil-hunting expedition to northern Arizona. Lead by Jesse Williams, a Navajo Indian, they discovered the first remains of Dilophosaurus in 1942. Three skeletons were found within twenty feet of one another, although one was badly eroded. One, however, was almost complete, with only the front of the skull missing. The third provided the rest of the skull and much of the front of the body. It then took a further two years to remove all of the skeleton from the rock and make a wall mount suitable for display.
The first description was published by Samuel P. Welles in 1954, but at the time Dilophosaurus was considered a species of Megalosaurus. In 1964 however, Welles became concerned that the dating on the rock may have been inaccurate and returned to the site to confirm it. The dating was in fact correct, but Welles found an excellent fourth skeleton nearby - the first to display the distinctive double crest. In 1970, with a more complete skeleton, Welles was forced to reconsider his earlier conclusions about the animal. Rexamination of the earlier specimens showed that the two crests had been pushed together and the reconstructors had assumed they were part of a displaced cheek bone. The revised account, recognising Dilophosaurus as a distinct genus, was finally published in 1984. In total, they are now around half a dozen specimens, young and adult.
Description
Dilophosaurus was a bipedal theropod, and hence a carnivore. It lived in the early Jurassic period; more specifically, the late Sinemurian to Pliensbachian, around 201 to 189 million years ago. It lived in what is now Arizona, USA. Adults were around 5.8 metres in length, and 1.5m tall to the hip, making it one of the largest carnivores of the time. Typical weight was 300kg to 450kg.
The neck, as for most theropods of this size, was S-shaped and highly flexible. The jaws were slender and loosely attached to the skull, and were distinctly crocodilian. The teeth were very narrow and sharp, and formed a separate bunch at the front of the jaw. For a dinosaur of this type, the three-fingered hands were rather large and this suggests that they were actually the main killing weapon. The jaws were rather fragile for such high-impact usage. It's even possible that Dilophosaurus was a scavenger. In fact, the hands were probably also used to tear lumps of flesh from the dead carcass. The feet were technically four-clawed, but one was a dewclaw. The central toe was longer; typical for a theropod. The long, thin legs were around 1.65m in length, and gave Dilophosaurus a stride length of about 2.13m.
The distinctive feature of Dilophosaurus was the pair of crests on top of the head. These narrow bony crests were not found attached to the skull, but paleontologists believe they ran parallel from the front to the back of the skull. They was also a short 'prong' at the rear, that stuck out to the side. It is conjectured that these were a display structure, like the tail of a peacock. If this were the case, the females would not have had such a crest, and classification of future specimens would be more difficult. There is no definitive theory as yet.
The fact that the first specimens were found in a group of three may mean that Dilophosaurus hunted in packs. However, it is impossible to be certain from one find if this was the case.
Jurassic Park
Many people will remember Dilophosaurus as the poison-spitter from Jurassic Park, which blinded and then ate Dennis Nedry. Of course, Stan Winston took a fair number of liberties with the original lizard for the purpose of their model. In fact, the real Dilophosaurus was considerably larger than that of the film! There's also no evidence of a neck frill nor poison glands. Indeed, as the largest predator of the time, these would have been superfluous features. The model was also given a perfectly smooth jaw, while the real dinosaur had a rather charming subnarial gap (kink in the jaw), between the maxilla and premaxilla.
Classification
- Order: Saurischia
- Sub-order: Theropoda
- Family: Megalosauria
- Genus: Dilophosaurus
Welles' original species was D. wetherilli ("Wetherill's two ridged lizard"). Hu named D. sinensis ("two ridged lizard from China") in 1993, from remains in Yunnan, China. D. sinensis is actually the most complete skeleton available. The crests are so much larger than those of the type species that is may well not belong to this genus. Welles himself described another species from Arizona, D. breedorum ("The Breeds' two ridged lizard"), with Pickering in 1999. However, it is possible that this species is actually a young D. wetherilli.
The initial confusion over classification was a result of the crests being missing from the first specimens. Without these features, Dilophosaurus was physically were similar to the earlier Megalosaurus. However, there is still some debate over classification. Traditionally, Dilophosaurus is placed as a Megalosaurid. However, the slender legs and tail, flexible neck, hollow bones and narrow jaws make it seem more like a very large coelurosaurid, like as Coelophysis. There seem to be as many different classifications of Dilophosaurus as there are sources; some placing it firmly in Coelurosauria, others in Halticosauria. If you have a definitive up-to-date classification, please /msg me!
Credit must be given to Dilophosaurus' discover, Sam Welles, who has an excellent online tour on the subject of his biggest discovery at http://www.ucmp.berkeley.edu/dilophosaur/intro.html. Check it out if you can.