Deinocheirus

Deinocheirus (meaning 'terrible hand') is a genus of very large ornithomimosaurian dinosaur that lived in what is now southern Mongolia during the late Cretaceous period around 70 million years ago. The genus Deinocheirus contains one species, Deinocheirus mirificus. D. mirificus was long thought of as a very mysterious dinosaur, known only from a set of gigantic fossil arm bones. The discovery of more complete skeletons helped to solve this longstanding mystery, revealing a very strange, giant, bipedal omnivore.

Deinocheirus measured up to 11 m (36 ft) long, and had an estimated weight of 6.358 t (6.258 long tons; 7.008 short tons). Though it had many of the typical skeletal features of its group, its overall appearance was very different from its relatives. While other ornithomimosaurians were light and fleet-footed, Deinocheirushad evolved to outsize its predators, and effectively became slower and bulkier.

Though the arms of Deinocheirus have a considerable absolute size, being the longest of any known theropod with the exception of Therizinosaurus, they are not very long relative to the shoulder girdle, the ratio being less than that with most ornithomimosaurs. The shoulder-blade is long and narrow. The humerus is relatively slender. The ulna and radius too are elongated and not very firmly connected to each other in a syndesmosis. The metacarpus is long compared to the fingers. The hand had good mobility relative to the lower arm but was capable of only a limited flexing motion, unable to close in grasping. The fingers are about equal in length to each other, the first being the stoutest and the second the longest. Only the claw of the left second finger has been preserved in its entirety; it has a diameter of 196 millimetres and a length along its outer curvature of 323 millimetres.