Deinonychus is a spectacular, but fairly small dinosaur. It measured about three and a half feet tall, and about nine feet long. Its weight is estimated at 150 pounds. By hunting in groups, members of a Deinonychus pack could have brought down dinosaurs much larger than themselves. In fact, the bones of several individuals of Deinonychus have been found with the skeleton of a large plant eating dinosaur, called Tenontosaurus.
Deinonychus belongs to a family of dinosaurs called dromaeosaurs. They all share the same characteristics a lightly built skull with sharp backwardly curved teeth, elongated arms and hands with sharp claws, and an extraordinary sickle-like second toe claw which was carried raised off the ground to protect the sharp point. Dromaeosaurs probably had keen vision and their brains were relatively large for a dinosaur. The dromaeosaurs lived throughout the Cretaceous period, 140 to 65 million years ago.
Deinonychus was highly specialized for swift movement and savage attack. With its terrible claw flicked forward it slashed its prey with one foot while standing on the other. This kind of behavior required good coordination, excellent eyesight and a high level of energy. By hunting in packs they may have brought down prey much larger than itself.