Deinocheirus
A large, bulky ornithomimosaur with a hadrosaur-like skull.
Deinocheirus is a genus of large ornithomimosaur that lived during the Late Cretaceous around 70 million years ago. The first remains, consisting of a pair of massive arms, shoulder girdles, and a few other bones, were discovered in the Nemegt Formation of Mongolia in 1965. This specimen became the holotype of the only species, *Deinocheirus mirificus*, named in 1970; the genus name means "horrible hand" in Greek. For nearly fifty years, no further fossils were found, leaving the animal's appearance and lifestyle a mystery. This changed in 2014 with the description of two more complete specimens, parts of which had been looted from Mongolia years earlier but were repatriated that same year. Deinocheirus was the largest known ornithomimosaur, a bulky animal that nonetheless had many hollow, weight-saving bones. Its arms, among the largest of any bipedal dinosaur, bore large, blunt claws on three-fingered hands. The legs were relatively short with blunt claws, and the vertebrae featured tall neural spines forming a sail along the back. The tail ended in vertebrae resembling a pygostyle, indicating a fan of feathers. The skull was long, with a wide bill and deep lower jaw similar to those of hadrosaurs. Initially classified within Carnosauria, its relationship to ornithomimosaurs was soon recognized. More complete remains later showed it to be a primitive ornithomimosaur, most closely related to *Garudimimus* and *Beishanlong* within the family Deinocheiridae. Unlike other ornithomimosaurs, members of this group were not built for speed. Deinocheirus is thought to have been omnivorous; its skull suggests a plant-based diet, fish scales were found with one specimen, and gastroliths were present in the stomach region. The large claws may have been used for digging and gathering plants. Bite marks on its bones have been attributed to the tyrannosaurid *Tarbosaurus*.
- lived
- Late Cretaceous, around 70 million years ago
- field
- Paleontology
- known_for
- Largest ornithomimosaur; enormous arms with blunt claws; long-mysterious due to fragmentary remains
Lore & Background
Deinocheirus was a large ornithomimosaur from the Late Cretaceous, known for its unusual build and massive forelimbs. Its most distinctive feature was its arms, among the largest of any bipedal dinosaur, ending in three-fingered hands with large, blunt claws. The skull was long, with a wide bill and a deep lower jaw reminiscent of hadrosaurs. The animal had a bulky body, but many of its bones were hollow to reduce weight. Its vertebrae bore tall neural spines that formed a sail-like structure along the back, and most vertebrae and other bones were highly pneumatised by air sacs. The legs were relatively short and ended in blunt claws. The tail featured pygostyle-like vertebrae, indicating a fan of feathers. Deinocheirus is thought to have been omnivorous, with a skull shape suggesting plant consumption, fish scales found with one specimen, and gastroliths in the stomach region. The large claws may have been used for digging and gathering plants. Bite marks on its bones have been attributed to the tyrannosaurid *Tarbosaurus*. The genus was first discovered in the Nemegt Formation of Mongolia, and for decades only the arms and shoulder girdle were known, making it one of the most enigmatic dinosaurs. Later, more complete specimens revealed its full anatomy and confirmed it as a primitive ornithomimosaur, closely related to *Garudimimus* and *Beishanlong* within the family Deinocheiridae. Unlike other ornithomimosaurs, members of this group were not adapted for speed.
Reader's Guide
Deinocheirus is significant as the largest known ornithomimosaur and for resolving a long-standing paleontological mystery. Its classification was initially uncertain, placed in Carnosauria, but later shown to be a primitive ornithomimosaurian, closely related to Garudimimus and Beishanlong within Deinocheiridae. Unlike other ornithomimosaurs, it was not adapted for speed. Its skull shape indicates an omnivorous diet of plants and fish, supported by fish scales found with one specimen and gastroliths in the stomach region. The large claws may have been used for digging and gathering plants. Bite marks on its bones have been attributed to the tyrannosaurid Tarbosaurus. The discovery of more complete specimens also highlighted the problem of fossil poaching, as parts of the new specimens had been looted and later repatriated. Deinocheirus remains a key example of how fragmentary fossils can be reinterpreted with new finds.
Did You Know?
- The genus name Deinocheirus is Greek for 'horrible hand'.
- Bite marks on Deinocheirus bones have been attributed to the tyrannosaurid Tarbosaurus.
Frequently Asked Questions
What is Deinocheirus?
Deinocheirus is a genus of large ornithomimosaur that roamed during the Late Cretaceous, roughly 70 million years ago. It holds the record as the biggest member of the ornithomimosaur family, featuring a stocky build, a sail-like ridge along its back, and a skull that closely resembles a hadrosaur's.
What are Deinocheirus's most distinctive physical features?
Its most eye-catching traits are the enormous arms ending in broad, blunt claws, a heavy and bulky torso, and a sail-like structure running down its spine. It also carried a long, hadrosaur-like skull, which was a surprising find for an animal classified as an ornithomimosaur.
How large was Deinocheirus compared to other dinosaurs?
Deinocheirus was the largest ornithomimosaur ever identified, with a body and arm span far exceeding those of its more slender relatives. Its sheer bulk and disproportionately huge forelimbs set it apart from the rest of its family.
Where and when did Deinocheirus live?
Deinocheirus inhabited what is now Mongolia during the Late Cretaceous, approximately 70 million years ago. Its remains come from the Nemegt Formation, a sedimentary deposit in Mongolia that has also produced fossils of many other dinosaur species.
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