Utahraptor (meaning “Utah thief”) is the largest known member of the theropod dinosaur family Dromaeosauridae. Utahraptor is known from a well-preserved skeleton found in 1991 in Utah, USA and fragmentary remains from South America.
It was the largest of a group of lightly-built carnivores, called the dromaeosaurs (‘swift lizards’). Utahraptor had large eyes, long grasping hands with large, sharp ripping claws. Its toe joints were specially enlarged so that its massive claw could be raised upward and backward to avoid damage while running. But when used in attack, its claw flexed forward as the animal kicked out. Swinging in a wide arc its huge 20 cm slashing claw would produce terrible wounds enabling a Utahraptor to cripple and kill animals much larger than itself.
The unique wrist-joints of the dromaeosaurs allowed the hands to pivot sideways, an action similar to the folding of a bird’s wing.