page_title: Deinocheirus
section_title: Description
hierarchical_section_title: Deinocheirus / Description
caption_attribution_description: English: Deinocheirus mirificus restoration. Based on the skeletal diagram and description in Lee et al. (2014). Lee, Y.N. (2014). "Resolving the long-standing enigmas of a giant ornithomimosaur Deinocheirus mirificus". Nature 515 (7526): 257–260. DOI:10.1038/nature13874.
context_page_description: Deinocheirus is a genus of large ornithomimosaur that lived during the Late Cretaceous around 70 million years ago. In 1965, a pair of large arms, shoulder girdles, and a few other bones of a new dinosaur were first discovered in the Nemegt Formation of Mongolia. In 1970, this specimen became the holotype of the only species within the genus, Deinocheirus mirificus; the genus name is Greek for "horrible hand". No further remains were discovered for almost fifty years, and its nature remained a mystery. Two more complete specimens were described in 2014, which shed light on many aspects of the animal. Parts of these new specimens had been looted from Mongolia some years before, but were repatriated in 2014.
  Deinocheirus was an unusual ornithomimosaur, the largest of the clade at 11 m long, and weighing 6.4 t. Though it was a bulky animal, it had many hollow bones which saved weight. The arms were among the largest of any bipedal dinosaur at 2.4 m long, with large, blunt claws on its three-fingered hands. The legs were relatively short, and bore blunt claws. Its vertebrae had tall neural spines that formed a "sail" along its back.
context_section_description: Deinocheirus is the largest ornithomimosaurian (ostrich dinosaur) discovered; the largest known specimen measured about 11–12 m (36–39 ft) long, with an estimated weight of 6.4–7 t (7.1–7.7 short tons), and an estimated hip height of 4.4 m (14 ft). The two other known specimens are smaller, the holotype being 94% as big while the smallest, a subadult, only 74% as big. When only the incomplete holotype arms were known, various sizes were extrapolated from them by different methods. A 2010 study estimated the hip height of Deinocheirus to be 3.3–3.6 m (11–12 ft). The weight had previously been estimated between 2 tonnes (2.2 short tons) to 12 tonnes (13 short tons). Enormous sizes were also suggested by comparing the arms with those of tyrannosaurs, even though members of that group did not have large arms in proportion to their body size.
  The only known skull, belonging to the largest specimen, measures 1.024 m (3.36 ft) from the premaxilla at the front to the back of the occipital condyle. The widest part of the skull behind the eyes is only 23 cm (9.1 in) wide in comparison. The skull was similar to those of other ornithomimosaurs in being low and narrow, but differed in that the snout was more elongated. The skull bone walls were rather thin, about 6 mm (0.24 in). It had a rounded, flattened beak, which would have been covered by keratin in life. The nostrils were turned upwards, and the nasal bone was a narrow strap that extended up above the eye sockets. The outer diameter of the sclerotic rings in the eyes was small, 8.4 cm (3.3 in), compared to the size of the skull. The lower temporal fenestrae, openings behind the eyes, were partially closed off by the jugal bones, similar to Gallimimus. The jaws were toothless and down-turned, and the lower jaw was very massive and deep compared to the slender and low upper jaw. The relative size of the lower jaw was closer to that of tyrannosaurids than to other ornithomimosaurs. The snout was spatulate (flared outwards to the sides) and 25 cm (9.8 in) wide, which is wider than the skull roof. This shape was similar to the snout of duck-billed hadrosaurids.
  Deinocheirus and Therizinosaurus possessed the longest forelimbs known for any bipedal dinosaurs. The holotype forelimbs measure 2.4 m (7.9 ft) long — the humerus (upper arm bone) is 93.8 cm (36.9 in), the ulna 68.8 cm (27.1 in), and the hand is 77 cm (30 in) — including the 19.6 cm (7.7 in) long recurved claws. Each scapulocoracoid of the shoulder girdle has a length of 1.53 m (5.0 ft). Each half of the paired ceratobranchialia measure 42 cm (17 in). The shoulder-blade was long and narrow, and the deltopectoralis crest was pronounced and triangular. The upper arm (humerus) was relatively slender, and only slightly longer than the hand. The ulna and radius (lower arm bones) were elongate and not firmly connected to each other in a syndesmosis. The metacarpus was long compared to the fingers. The three fingers were about equal in length, the first being the stoutest and the second the longest. Various rough areas and impressions on the forelimbs indicate the presence of powerful muscles. Most articular surfaces of the arm bones were deeply furrowed, indicating that the animal had thick pads of cartilage between the joints. Though the arms of Deinocheirus were large, the ratio between them and the shoulder girdle was less than that of the smaller ornithomimosaur Ornithomimus. The arm bones of Deinocheirus were similar in proportions to those of the small theropod Compsognathus. The wishbone (furcula), an element not known from any other ornithomimosaurs, was U-shaped. The hindlimbs were relatively short, and the thigh bone (femur) was longer than the shin bone (tibia), as is common for large animals. The metatarsus was short and not arctometatarsalian, as in most other theropods. The claw bones of the feet were blunt and broad-tipped instead of tapered, unlike other theropods, but resembled the unguals of large ornithischian dinosaurs. The proportions of the toe bones resembled those of tyrannosaurs, due to the large weight th
caption: Life restoration
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