Deinocheirus

Deinocheirus (/ˌdaɪnoʊˈkaɪrəs/ DY-no-KY-rəs) 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 (36 ft) long, and weighing 6.5 t (7.2 short tons). 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 (7.9 ft) 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. Most of the vertebrae and some other bones were highly pneumatised by invading air sacs. The tail ended in pygostyle-like vertebrae, which indicate the presence of a fan of feathers. The skull was 1.024 m (3.36 ft) long, with a wide bill and a deep lower jaw, similar to those of hadrosaurs.

The classification of Deinocheirus was long uncertain, and it was initially placed in the theropod group Carnosauria, but similarities with ornithomimosaurians were soon noted. After more complete remains were found, Deinocheirus was shown to be a primitive ornithomimosaurian, most closely related to the smaller genera Garudimimus and Beishanlong, together forming the family Deinocheiridae. Members of this group were not adapted for speed, unlike other ornithomimosaurs. Deinocheirus is thought to have been omnivorous; its skull shape indicates a diet of plants, fish scales were found in association with one specimen and gastroliths were also present in the stomach region of the specimen. The large claws may have been used for digging and gathering plants. Bite marks on Deinocheirus bones have been attributed to the tyrannosaurid Tarbosaurus.

The first known fossil remains of Deinocheirus were discovered by Polish palaeontologist Zofia Kielan-Jaworowska on July 9, 1965, at the Altan Ula III site (coordinates: 43°33.987′N 100°28.959′E / 43.566450°N 100.482650°E / 43.566450; 100.482650) in the Nemegt Basin of the Gobi Desert. She was part of a Polish group accompanied by Mongolian palaeontologist Rinchen Barsbold during the 1963–1965 Polish-Mongolian palaeontological expeditions, which were organised by the Polish Academy of Sciences and the Mongolian Academy of Sciences. The crew spent July 9–11 excavating the specimen and loading it onto a vehicle. A 1968 report by Kielan-Jaworowska and Naydin Dovchin, which summarised the accomplishments of the expeditions, announced that the remains represented a new family of theropod dinosaur.

The specimen was discovered on a small hill in sandstone, and consists of a partial, disarticulated skeleton, most parts of which had probably eroded away at the time of discovery. The specimen consisted of both forelimbs, excluding the claws of the right hand, the complete shoulder girdle, centra of three dorsal vertebrae, five ribs, gastralia (belly ribs), and two ceratobranchialia. The specimen was made the holotype of Deinocheirus mirificus, named by Halszka Osmólska and Ewa Roniewicz in 1970. The generic name is derived from Greek deinos (δεινός), meaning "horrible", and cheir (χείρ), meaning "hand", due to the size and strong claws of the forelimbs. The specific name comes from Latin and means "unusual" or "peculiar", chosen for the unusual structure of the forelimbs. The Polish-Mongolian expeditions were notable for being led by women, among the first to name new dinosaurs. The original specimen number of the holotype was ZPal MgD-I/6, but it has since been re-catalogued as MPC-D 100/18.

The paucity of known Deinocheirus remains inhibited a thorough understanding of the animal for almost half a century onwards, and the scientific literature often described it as among the most "enigmatic", "mysterious", and "bizarre" of dinosaurs. The holotype arms became part of a traveling exhibit of Mongolian dinosaur fossils, touring various countries. In 2012, Phil R. Bell, Philip J. Currie, and Yuong-Nam Lee announced the discovery of additional elements of the holotype specimen, including fragments of gastralia, found by a Korean-Mongolian team which re-located the original quarry in 2008. Bite marks on two gastralia were identified as belonging to Tarbosaurus, and it was proposed that this accounted for the scattered, disassociated state of the holotype specimen.

In 2013, the discovery of two new Deinocheirus specimens were announced before the annual Society of Vertebrate Paleontology (SVP) conference by Lee, Barsbold, Currie, and colleagues. Housed at the Mongolian Academy of Sciences, these two headless individuals were given the specimen numbers MPC-D 100/127 and MPC-D 100/128. MPC-D 100/128, a subadult specimen, was found by scientists in the Altan Ula IV locality (coordinates: 43°36.091′N 100°27.066′E / 43.601517°N 100.451100°E / 43.601517; 100.451100) of the Nemegt Formation during the Korea-Mongolia International Dinosaur Expedition in 2006, but had already been damaged by fossil poachers. The second specimen, MPC-D 100/127, was found by scientists in the Bugiin Tsav locality (coordinates: 43°54.025′N 99°58.359′E / 43.900417°N 99.972650°E / 43.900417; 99.972650) in 2009. It is slightly larger than the holotype, and it could be clearly identified as Deinocheirus by its left forelimb, and therefore helped identify the earlier collected specimen as Deinocheirus. The specimen had also been excavated by poachers, who had removed the skull, hands and feet, but left behind a single toe bone. It had probably been looted after 2002, based on money left in the quarry. Skulls, claw bones and teeth are often selectively targeted by poachers on the expense of the rest of the skeletons (which are often vandalized), due to their saleability. Currie stated in an interview that it was a policy of their team to investigate quarries after they had been looted and recover anything of significance, and that finding any new Deinocheirus fossils was cause for celebration, even without the poached parts. A virtual model of Deinocheirus revealed at the SVP presentation brought applause from the crowd of attending palaeontologists, and the American palaeontologist Stephen L. Brusatte stated he had never been as surprised by a SVP talk, though new fossils are routinely presented at the conference.

After the new specimens were announced, it was rumoured that a looted skull had found its way to a European museum through the black market. The poached elements were spotted in a private European collection by the French fossil trader François Escuillé, who notified Belgian palaeontologist Pascal Godefroit about them in 2011. They suspected the remains belonged to Deinocheirus, and contacted the Korean-Mongolian team. Escuillé subsequently acquired the fossils and donated them to the Royal Belgian Institute of Natural Sciences. The recovered material consisted of a skull, a left hand, and feet, which had been collected in Mongolia, sold to a Japanese buyer, and resold to a German party (the fossils also passed through China and France). The team concluded that these elements belonged to specimen MPC-D 100/127, as the single leftover toe bone fit perfectly into the unprepared matrix of a poached foot, the bone and matrix matched in colour, and because the elements belonged to an individual of the same size, with no overlap in skeletal elements. On May 1, 2014, the fossils were repatriated to Mongolia by a delegation from the Belgian Museum, during a ceremony held at the Mongolian Academy of Sciences. The reunited skeleton was deposited at the Central Museum of Mongolian Dinosaurs in Ulaanbaatar, along with a Tarbosaurus skeleton which had also been brought back after being stolen. American palaeontologist Thomas R. Holtz stated in an interview that the new Deinocheirus remains looked like the "product of a secret love affair between a hadrosaur and Gallimimus".