Deinocheiridae

Deinocheiridae is an extinct family of ornithomimosaurian dinosaurs. Its members lived in Asia and North America between the Aptian and Maastrichtian ages. The family was first named in 1970 by Halszka Osmólska and Roniewicz, who included only the type genus *Deinocheirus*. A 2014 study by Yuong-Nam Lee and colleagues, published in *Nature*, confirmed Deinocheiridae as a valid family. Their phylogenetic analysis, based on newly discovered complete skeletons, placed *Beishanlong* as the most primitive member, *Garudimimus* in an intermediate position, and *Deinocheirus* as the most derived. This grouping made the family Garudimimidae, named by Rinchen Barsbold in 1981, a junior synonym of Deinocheiridae. The group existed from about 115 to 69 million years ago: *Beishanlong* lived from 115 to 100 mya, *Garudimimus* from 98 to 83 mya, and *Deinocheirus* from 71 to 69 mya. Other genera possibly included are *Paraxenisaurus*.

Deinocheirids can be identified by several skeletal features: the bones of the lower arm are well separated, the flexor tubercles on the manual claws are positioned closer to the attachment point, and the cnemial crest of the tibia projects prominently toward the front and top. Unlike ornithomimids, they lack an arctometatarsalian condition in the foot. While *Deinocheirus* is toothless, other deinocheirids like *Garudimimus* (which has a toothless beak but retains teeth in the upper jaw) and *Beishanlong* retain teeth.

When originally named, Osmólska and Roniewicz classified *Deinocheirus* as a carnosaurian and, due to its unusual arms, created the monotypic family Deinocheiridae. They placed it within the superfamily Megalosauroidea, inside the infraorder Carnosauria (then a paraphyletic group of all large theropods). At that time, the only other carnosaurian from the same period and region in Asia was the tyrannosaurid *Tarbosaurus*. Their diagnosis, based solely on *Deinocheirus*, described the family as "gigantic carnivorous dinosaurs with long, slender scapula and long fore limbs; manus with three, uniformly developed fingers, ending in strong, large claws." They limited the family’s temporal and geographic range to the Upper Cretaceous of the Upper Nemegt Formation in the Gobi Desert, Mongolia. They noted similarities to *Ornithomimus* but kept the groups separate, citing possible convergence.