In the 1993 film Jurassic Park as well as the novel it is based on, one of the dinosaurs depicted is the Dilophosaurus. The film shows it with a frill around its neck and standing shorter than the actor Wayne Knight (5 ft 7 in) who plays the role of Dennis Nedry, killed by the Dilophosaurus which spits venom.
The real Dilophosaurus had no neck frills, was a monster at a length of 20 ft, and did not spit venom. When Jurassic Park was shot, Dilophosaurus was already known to be a large dinosaur, while the frills and the venom were fictionalised embellishments. Until recently, the picture of Dilophosaurus was far from complete.
Now, a new comprehensive analysis of Dilophosaurus fossils is helping create a more complete description. Among the new findings, one was that Dilophosaurs had much in common with modern birds. The study, led by Adam Marsh, then a PhD Student at University of Texas at Austin and now lead palaeontologist at Petrified Forest National Park, and co-authored by UTexas professor Timothy Rowe, is published in the Journal of Paleontology.
What it is Dilophosaurus?
Dilophosaurus lived in what is now North America during the Early Jurassic, about 183 million years ago. The first fossils were discovered in Arizona in the 1940s.
“Dr Samuel Welles of the University of California Museum of Paleontology was told about a dinosaur skeleton on the Navajo Nation, and dug two specimens of Dilophosaurus up in 1942, and a third was found in 1964,” lead author Marsh told The Indian Express by email. Marsh’s co-author Rowe and his team found two other specimens in the late 1990s and early 2000s.
Welles initially described the early finds as a new species in the genus Megalosaurus. Following further studies, Welles in 1970 assigned the species to the genus Dilophosaurus, and named the species Dilophosaurus wetherilli.
Why is it being studied now?
In Marsh’s words, “until this study, nobody knew what Dilophosaurus looked like or how it evolved”. For his PhD, Marsh conducted an analysis of the five most-complete Dilophosaurus specimens, including the two discovered by Rowe.
“The new thing about size in this paper.” Marsh said in reply to a question, “is that we demonstrate a growth series based on five individuals (including a partial skeleton of a juvenile) and discuss potential variation that may be attributable to age or interspecific variation.”
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In what ways is it different from the depiction in Jurassic Park?
At 20 ft in length, Dilophosaurus was the largest land animal of its time, much unlike the smaller-than-a-human film version. Early descriptions give Dilophosaurus a fragile crest and weak jaws, which influenced its depiction as a venom-spitting dinosaur. Marsh found, instead, that the Dilophosaurus jawbones show signs of serving as scaffolding for powerful muscles.
The book and film depictions came at a time when Dilophosaurus had already been published as a larger animal. “The fictionalised version was made to be smaller. Which is fine, because it is fiction, after all,” Marsh said,
What is common with modern birds?
Marsh found that some bones were mottled with air pockets, which would have helped reinforce the skeleton, including its dual crest. Modern birds — and the world’s most massive dinosaurs — also have bones filled with air. In both cases, the air sacs lighten the load, which helped big dinosaurs manage their bulky bodies and birds take to the skies.
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Many birds use the air sacs to perform other functions, from inflating stretchy areas of skin during mating rituals, to creating booming calls and dispersing heat. From the arrangement of air pockets and ducts in the Dilophosaurus skull, the new research suggests that the dinosaur may have been able to perform similar feats.
Does that mean that other massive dinosaurs with such air sacs, too, are similar to birds?
Marsh said it means that air sacs predate birds, that birds inherited the air sac system from a common ancestor that is also shared by meat-eating and long-necked dinosaurs that also have air sacs. “I think most dinosaurs probably were more like birds than lizards physiologically,” he said.