DROMAEOSAUR

any member of a family (Dromaeosauridae) of theropod dinosaurs that flourished in Asia and North America during the Cretaceous Period (from 144 to 66.4 million years ago). The special bodily features that characterized the dromaeosaurs have led to their being grouped in their own infraorder, the Deinonychosauria, meaning terrible-clawed lizards. Dromaeosaurs were medium-sized, lightly built, agile, fast-running carnivores that were among the most effective predators of their time. They were bipedal, and the second toe of each foot was extremely flexible and bore a specialized killing claw, or talon; those of Deinonychus measured 13 cm (5 inches) in length. Dromaeosaurs had large heads equipped with many sharp, slashing teeth, and their long arms ended in long, three-clawed hands that were useful for grasping. Their tails were also unusually long and could be held rigid with the help of bundles of slim bony rods growing out of the tail vertebrae. Dromaeosaurs' hunting technique appears to have involved running down their prey (probably small- to medium-sized herbivores) and grasping it with the front claws while delivering slashing kicks with the killing talon on one of the hind legs. Dromaeosaurs may have held this pose on one foot by using the rigidly outstretched tail as a counterbalance, or they may have attacked using both feet, in a single leaping action. Their relatively large brains enabled them to carry out these complex movements with a degree of coordination unusual among reptiles. The largest species of dromaeosaur, Deinonychus, averaged 3 m (10 feet) in length, stood about 1.8 m tall, and weighed up to 70 kg (150 pounds). Dromaeosaurus and Velociraptor were smaller species reaching a length of 1.8 m.