Utahraptor is a really large species of Dromaeosaur,or Raptor.It is much larger than it's relatives,Deinonychus and Velociraptor,wich also appear in the game.
They are seen as a mini-boss quite early in the game,but in a later level,four of them come and try to kill you.They appear to have a very thick reptilian hide,spikes and they seem to prey on their cousins(like Deinonychus),because in their first appearance,they seem to run after some Deinonychus,before coming to attack you.
U-raptors are large at 25 feet long. A possible dinosaur may be larger called Megaraptor. Debate however is showing it to be more of a Spinosaur than a Raptor. Jurassic the Hunted U-Raptors are larger than your average Utahraptor and have large, thick scales.