Utahraptor

|- |(unranked)||Maniraptora

|- |(unranked)||Deinonychosauria

Utahraptor ostrommaysorum ("Utah thief") is the largest known member of the theropod dinosaur family Dromaeosauridae from the Barremian stage of the Lower Cretaceous period, and it was also one of the earliest.

Discovery and species

Kirkland, Gaston, and Burge discovered this dromaeosaurid in 1993 in Grand County, Utah, within the Cedar Mountain Formation . The type specimen is currently housed at the College of Eastern Utah; although Brigham Young University currently houses the largest collection of Utahraptor fossils.

The type species, Utahraptor ostrommaysorum, was named for the American paleontologist John Ostrom, from Yale University's Peabody Museum, and Chris Mays, of Dinamation International.

Characteristics

Like other dromaeosaurids, Utahraptor had a huge, bladelike claw on the second toe. The animal probably grasped its prey with its forelimbs while kicking with the hindlimbs. Up to 7 meters (20 feet) long and 500 kg (1000lbs) in weight, Utahraptor would have been a formidable predator (Kirkland et al. 1993). It has been speculated that packs might have been able to bring down a sauropod, although it is nearly impossible to know whether Utahraptor actually did live in packs.

Classification

It is thought that Utahraptor may be related to Dromaeosaurus (Kirkland et al. 1993) and the giant Mongolian dromaeosaurid Achillobator .

A slightly more detailed classification:

• Order Saurischia ("lizard hipped" dinosaurs)
  • Suborder Theropoda (bipedal carnivores)
    • Clade Tetanurae (advanced theropods)
      • Clade Coelurosauria
        • Clade Maniraptora (modern birds are maniraptors)
          • Clade Deinonychosauria (switchblade like claws)
            • Family Dromaeosauridae (the "raptors")
              • Genus Utahraptor