tell me about Dilophosaurus, one of my favorite of the "weird" theropods
Dilophosaurus is very much a “weird theropod” - so weird, in fact, that it literally defies classification.
Dilophosaurus was native to the southwestern United States during the Early Jurassic period - about 193 million years ago - and was the largest known carnivore of its native time and place. It’s primarily known for the twin crests on its head, the purposes of which have long been debated. They may have been used to display to mates, intimidate rivals, or simply for the recognition of individuals within the species.
As far as we know, Dilophosaurus did not actually have an extensible neck frill or the ability to spit poison.
When it was initially discovered in 1954, Dilophosaurus was described as a new species of Megalosaurus, as happens to most theropods who can’t be safely classified elsewhere. Later, more careful examinations of Dilophosaurus fossils led paleontologists to believe that it was a large relative of Coelophysis. Even later, it was classified in its own family, “Dilophosauridae”, belonging to a more advanced clade of theropods. It was grouped with Cryolophosaurus; then the two dinosaurs were moved into separate families. Then it was placed back into a family with Coelophysis!
The problem with Dilophosaurus is that it’s too transitional. Its anatomy resembles both Coelophysis and more advanced theropods, and it’s difficult to say with certainty to which group it was more closely related.
Despite our lack of taxonomic certainty in regards to Dilophosaurus, we do know a great deal else about it. The sandy terrain of Early Jurassic Arizona has preserved a large number of fossilized Dilophosaurus footprints, including a fossilized “sitting imprint” that revealed Dilophosaurus to have a bird-like resting posture.
In addition, a new specimen of Dilophosaurus, discovered and described just this year, has broken the record for “most injuries in a single dinosaur specimen”, with multiple partially healed forelimb breakages; a hand that healed improperly and became deformed; and a genetic bone growth abnormality that was known in modern birds, but not previously in dinosaurs. Its injuries were likely incurred in an accident - a nasty fall, perhaps - and the extent to which they had healed reveals that the animal survived for months, if not years,after incurring them.
Dilophosaurus is a fairly well known - and fairly misunderstood - early theropod dinosaur. It lived around 193 million years ago in the Sinemurian stage of the early Jurassic Period. At first it was named a species of Megalosaurus, however upon the discovery of a second specimen in which the crest was clearly visible it was renamed Dilophosaurus. The fossil evidence of Dilophosaurus indicate that the fossils found are probably from subadult individuals. It was discovered in the Kayenta Formation in Arizona. Dilophosaurus was a bipedal predator, and was probably a fast and agile runner. As several individuals were found together as fossils, there is some evidence that Dilophosaurus might have lived in social groups (however, this could have been attributed to other reasons as well, such as all having been swept away together in a flash flood.) It probably lived near river environments, allowing it to prey on a variety of organisms. It lived in the same environment as many other early dinosaurs, such as Megapnosaurus, Kayentavenator, Sarahsaurus, Scelidosaurus, and Scutellosaurus. It also lived in the same environment as the pterosaur Rhamphinion. Dilophosaurus remains have also been found in the Dharmaram Formation in Andhra Pradesh, India. This specimen shared its environment with a crocodilian, a sauropodomorph, and Lamplughsaura.
Dilophosaurus was a large predator, around seven meters long, and around the height of a person. It had a pair of rounded crests on its skull, which were most definitely used for display. A notch in its upper jawline allowed for Dilophosaurus to have an almost crocodile like mouth, similar to the later Spinosaurid dinosaurs. This could indicate that Dilophosaurus would occasionally prey on fish as well as terrestrial animals. There is no indication of sexual dimorphism in the species. The crest could have been used for attracting mates or intimidating other members of the social group, or it could have been used to distinguish separate species from one another. It grew rapidly, according to the bone structure. Trackways have been found that are attributed to Dilophosaurus, or at least a similar species, in Arizona, Poland, Sweden, Massachusetts, and Connecticut. Furthermore, trackways in Massachusetts also have what appear to be feather imprints alongside the footprints, suggesting that Dilophosaurus - a still very early theropod - had feathers! (Or at least, a very early form of feathers). This would indicate that the evolution of feathers started very early in the dinosaur family tree, allowing for Archaeopteryx to be a real contender for one of the earliest birds.
By Leandra Walters, Phil Senter, James H. Robins, CC BY 2.5, from Wikipedia
Dilophosaurus is very well known in popular culture due to the Jurassic Park franchise. However, the film (and the book) got Dilophosaurus quite wrong. Dilophosaurus was, to begin with, much larger than the film Dilophosaurus; Dilophosaurus in the film was made much smaller than usual so as not to be confused with the Velociraptor. However, Velociraptor in real life was much smaller than in Jurassic Park, and Dilophosaurus was bigger. Furthermore, there is no fossil evidence that Dilophosaurus supported a neck frill, or that it could spit venom. However, many further pop culture depictions of dinosaurs depict Dilophosaurus with these features, creating a large misrepresentation of the animal, which is rather unfortunate.