Dinosaurs are not completely extinct, as many might believe. It has been widely accepted for more than 30 years that birds are direct descendants of small theropods (meat-eating dinosaurs) called maniraptorans. This followed the discovery of a dromaeosaurid (of the family Dromaeosauridae) maniraptoran called Deinonychus, which showed a novel feature in the hand skeleton: a half-moon shaped wrist bone that allowed a wide range of hand movement and folding. This feature, which facilitated the wrist rotation and hand folding regarded as the precursor to the flight stroke, is shared uniquely with the earliest known bird, Archaeopteryx, discovered more than 150 years ago from 147-million-year-old latest Jurassic rocks in Germany. Many other skeletal features of Archaeopteryx and maniraptorans show a close resemblance. More impressive still are the impressions of wing and tail feathers, almost identical with those in modern birds, present in the fine-grained rock surrounding the skeletons of Archaeopteryx. The wings bear asymmetric primary and secondary feathers that confer aerodynamic properties necessary for flight.