DEINONYCHUS

genus of theropod dinosaurs that flourished in western North America during the Early Cretaceous Period (144 to 97.5 million years ago). A member of the dromaeosaur (q.v.) family, Deinonychus walked and ran on two legs, yet its killing devices, large sicklelike talons 13 cm (5 inches) long on the second toe of each foot, required it to stand on one foot while slashing at its prey with the other. The long, outstretched tail was enclosed in bundles of bony rods that grew out of the tail vertebrae, making it very rigid and thus an ideal balancing rod while the animal was running or attacking prey. Deinonychus measured about 2.44 m (813 feet) in length and weighed 4568 kg (100150 pounds). It was evidently a fast, agile predator whose large brain enabled it to perform relatively complex movements during the chase and kill.