Deinonychus (dĪˌnənĪˈkəs) [key] [Gr., = terrible claw], swift bipedal carnivorous dinosaur of the early Cretaceous period, approximately 119–93 million years ago. Fossil specimens have been discovered in Montana and Wyoming. Adults were around 10 ft (2.5 m) from head to tail and 1 ft (3 m) high. The second toe of each three-toed foot was modified into a long sickle-shaped claw, and the hands, each finger of which also ended in a claw, were adapted to grabbing prey. Deinonychus is thought to have been a very fast-moving predator. It belongs to the group of saurischian theropods [Gr., = beast feet] that includes Tyrannosaurus, Velociraptor, and living birds.