Dilophosaurus

Dilophosaurus (/daɪˌlɒfɵˈsɔrəs/ dy-lof-o-sawr-əs or /daɪˌloʊfɵˈsɔrəs/), meaning Double Crested Lizard, is a genus of theropod dinosaur from the Sinemurian stage of the Early Jurassic Period, about 193 million years ago. It is considered to be the very first large carnivorous dinosaur, measuring around 7 metres (23 ft) long and assumed to have weighed 500 kilograms (1,100 lbs). It is distinctly known from its two famous crests rounding above its skull that have made it famous.

Skin imprints seem to suggest that it had feathers but further study revealed these to be impressions of plant material.

Description
The most distinctive characteristic of Dilophosaurus is the pair of rounded crests on its skull, made up of extensions of the nasal and lacrimal bones. These are considered to be too delicate for anything but display purposes, and studies done by Gay in 2005 show no indication of sexual dimorphism being present in the skeleton, though no mention was made involving possible crest variation. Dodson noted in 1997 that cranial crests first appear in Dilophosaurus and later in other theropods.

The teeth of the genus are long, but have a fairly small base and expand basally. These teeth are comprised of 12 maxillary and up to 18 dentary, being smaller in the tip of the upper jaw. The second and third front teeth also feature serrations, which are absent in the first and fourth. Interestingly, there is a notch behind the first row of teeth, giving the creatures an almost crocodile-like appearance, in a manner similar to the putatively piscivorous spinosaurids.

Although primitive in the terms of Tyrannosaurus rex or Allosaurus, it was actually a very advanced predator at the time. For one, the braincase was significant enough to bear a feature of the top side all that was absent in other known ceratosaurians.

Region
Fossils of Dilophosaurus have been uncovered in Southwestern US (for instance, in the Navajo Indian Reservation, just west of Tuba City, Arizona) and possibly China.

Venomous Dilophosaur
Venomous dilophosauruses have been noted, appearing in Isla Nublar's Jurassic Park off of South America. These were genetically altered using spitting cobra DNA, and may in fact be related to the much smaller spitting variety, which are also venomous yet possess a frill (which may or may not be shed as the creature matures and reaches sizes where it no longer needs to intimidate with a false size increase). Considering that this variety were 10 feet tall while the spitters on Jurassic Park were only 3 feet tall and 5 feet long, it seems like a fairly plausible answer.

Spitting Dilophosaur
Spitting dilophosauruses have been noted, appearing in Isla Nublar's Jurassic Park off of South America as well as a military-controlled island. While both of these groups seem to have been genetically altered using spitting cobra DNA, and may in fact be related to the much larger venomous variety, perhaps simply being younger members of the species.

Despite this, spitting dilos were also witnessed by former Navy Seal Craig Dylan, seemingly back in the Early Jurassic after traveling accidentally through a warp in the Bermuda Triangle. This breed was insular, appearing on the island as far as anyone knows.

Jurassic Park
Dilophosaurus appeared in Jurassic Park. It was the first animal on the tour and later escaped and was known for killing Dennis Nedry. In Jurassic Park: The Game, which is an official follow-up to the first movie and is considered canonical, it is revealed that the dilophosaur was hunting with a pack.