Dilophosaurus (Greek: di for "two", lophos "crest", and sauros "lizard") was a theropod dinosaur from the Sinemurian stage of the Early Jurassic Period, about 193 million years ago. The first specimens were described in 1954, but it was not until over a decade later that the genus received its current name. It is one of the earliest known Jurassic theropods and one of the least understood.
Description
Dilophosaurus measured around six meters (20 ft) long and may have weighed half a ton. The most distinctive characteristic of Dilophosaurus is the pair of rounded crests on its skull, possibly used for display. Studies by Robert Gay show no indication that sexual dimorphism was present in the skeleton of Dilophosaurus, but says nothing about crest variation. The teeth of Dilophosaurus are long, but have a fairly small base and expand basally. Another skull feature was a notch behind the first row of teeth, giving Dilophosaurus an almost crocodile-like appearance, similar to the putatively piscivorous spinosaurid dinosaurs. This "notch" existed by virtue of a weak connection between the premaxillary and maxillary bones of the skull. This conformation led to the early hypothesis that Dilophosaurus scavenged off dead carcasses, with the front teeth being too weak to bring down and hold large prey.
Classification
Dilophosaurus may be a primitive member of the clade containing both ceratosaurian and tetanuran theropods. Alternatively, some paleontologists classify this genus as a large coelophysoid.
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