Deinocheirus

## DeinocheirusTerrible Hand

* **Skull Length** of 1 meter (3 feet, 4 inches)
* **Arm Length** of 2.4 meters (8 feet)
* **Hand Length** of 77 centimeters (2 feet, 6 inches)
* **Hand Claw Length** of 20 centimeters (8 inches)
* Relies on gastrolith stones to mash up food

***“ Deinocheirus. It's even taller than T. rex, and its massive duck-billed snout is very effective in gathering water plants. ”***

― **David Attenborough**, *Freshwater*
***Deinocheirus*** (Terrible Hand) is a genus of ornithomimosaurian theropod dinosaur that lived in the Nemegt Formation, Mongolia, 70 million years ago, during the Maastrichtian stage of the Late Cretaceous Period.

## Paleobiology

### Size and Physique

***“ With its feathered body and duck bill, the eight-ton Deinocheirus wades through an Asian wetland in search of relief from pesky biting flies. ”***

― The official Apple TV+ episode synopsis for *Freshwater*
*Deinocheirus* is a massive theropod, estimated in 2016 to be around 4.4 meters (14 feet) tall and 12 meters (36 feet) in length. As with most bulky animals, it had many hollow bones, some highly-pneumatized by invading air sacs, to help it save weight, though it was still a heavy animal, weighing around 6.5 - 7.3 metric tons (7.2 - 8 short tons). It is the largest ornithomimosaur ever discovered, having traded the sleek, ostrich-like body plan and speed of relatives like *Ornithomimus* for a slower but more massive form, and, along with its contemporary, the equally bizarre *Therizinosaurus*, it was one of the largest maniraptoriforms, with both having the longest necks of any theropod dinosaur, along with *Gigantoraptor*, an oviraptorosaur that lived in Mongolia more than 30 million years prior.

### Feathers

While feathers are known in smaller ornithomimosaurs, the extent of feathers on *Deinocheirus* is not fully clear. According to Darren Naish, lead consultant of Prehistoric Planet, the environment *Deinocheirus* lived in is understood to be cool, and dinosaurs may have been better at temperate control compared to big mammals, thus serving as somewhat of a justification for the thick coat of feathers on *Deinocheirus*.

### Bill

The skull of *Deinocheirus* is more than a meter long, with a wide duck-like bill, similar to those of hadrosaurs. Unlike hadrosaurs, however, which possess dental batteries (hundreds of teeth, stacked in rows to form a grinding surface), *Deinocheirus* has a toothless bill, with a low, slender upper jaw and a massive, deep lower jaw, hence, it cannot chew. In fact, the attachment points for the muscles responsible for jaw movement are small, indicating that *Deinocheirus* had a weak bite force. Instead, it only used its large, muscular tongue to force food to the back of the mouth, and compensated for the lack of chewing ability by relying on gastrolith stones in its gut to mash up food.

### Arms

***“ Water plants are rich in nutrients, and his huge, curved claws, eight inches long, enable him to dredge them up from deep beneath the surface. ”***

― **David Attenborough**, *Freshwater*
Along with *Therizinosaurus*, the arms of *Deinocheirus* were among the largest of any bipedal dinosaur, reaching 2.4 meters (8 feet) in length, with large, blunt, 20-centimeter (8-inch) claws on its three-fingered hands, earning it the name "Terrible Hand". The legs were relatively short, and bore blunt claws. Its vertebrae had tall neural spines that formed a "sail" along its back. The tail ended in pygostyle-like vertebrae, which indicate the presence of a fan of feathers.

### Prehistoric Planet's Depiction

On Prehistoric Planet, *Deinocheirus* is depicted with a thick coat of greenish-brown feathers, a yellow bill, and a ring of bare, blue skin within the facial area past the bill.

## Paleoecology

### Paleoenvironment

*Main: Nemegt Formation*

Main: Nemegt Formation

***“ In parts of Central Asia, heavy seasonal rains fill the rivers until eventually, they overflow their banks. The surrounding plains are flooded. ”***

― **David Attenborough**, *Freshwater*
*Deinocheirus* lived 70 million years ago in the Nemegt Formation, an area that would one day become the Gobi Desert in Mongolia. The formation shows evidence of a rich, humid environment with large river channels, tidal flats, and forests. On the show, *Deinocheirus* is shown wading through a swampy area, a river that overflowed its banks due to heavy rains, dredging up water plants from the bottom of the river.

### Paleofauna

*Deinocheirus* would have coexisted with similarly-large creatures like *Barsboldia*, *Nemegtosaurus*, *Opisthocoelicaudia*, and other, larger titanosaurs that may potentially rival *Argentinosaurus* in size. It also shared its habitat with small animals like *Mononykus*, *Prenocephale*, and velociraptorine dromaeosaurids. Due to its great height *Deinocheirus* would have been able to feed from relatively higher trees than some herbivores, and it would have been an intimidating sight to behold, being among the tallest and heaviest non-sauropod dinosaurs in the area alongside the large therizinosaur *Therizinosaurus*. Even a large *Tarbosaurus* (the apex predator of the region) would not have been able to bite any higher than the belly or thigh of an adult *Deinocheirus* or *Therizinosaurus*, and, though it has a tremendous, five-ton bite force, trying to do so would put the tyrannosaur within the striking range of the long, powerful clawed forearms of both animals. Even so, *Deinocheirus* is not completely immune to predation, as proven by *Tarbosaurus* bite marks on a *Deinocheirus* gastralia (ventral bone found between the sternum and pelvis), either due to scavenging or predation.

### Social Habits and Ingenuity

The lone male *Deinocheirus* in Freshwater is shown to be solitary. When his long arms and 8-inch claws proved unable to reach and scratch every part of his body, he rubs his body on a dead tree to get to places his arms can't reach. This can indicate a degree of intelligence on his part, able to recognize parts of the environment he can use to his advantage.

### Feeding Preferences

***“ This male feeds voraciously, having eaten very little during the long, dry season. ”***

― **David Attenborough**, *Freshwater*
*Deinocheirus* is said to have not eaten much during the dry season, hence, when the wet season begins, he wades through a swampy environment formed by a river that overflowed its banks, voraciously scooping up vegetation from the riverbed with his massive duck bill and huge arms, tipped with claws almost 20 centimeters (8 inches) in length. While *Deinocheirus* is depicted as living on a diet that consists almost entirely of wet vegetation, evidence of fish vertebrae and scales in one specimen's stomach indicates a degree of omnivory. Also found in its stomach are more than 1,400 gastroliths, indicating that it processed food in its gut rather than its jaws, which possess no teeth with which to chew up food.

## Appearance

  **Freshwater**, Segment III
**Setting**
Nemegt Formation, Gobi Desert, Mongolia

In the third segment of Freshwater, one male *Deinocheirus* is seen feasting on plants at the bottom of a swollen river, having eaten very little during the long, dry season. Unfortunately, he is pestered by flies, which prove to be irritating and even painful.

***“ He himself is a source of food for smaller creatures. Bloodsucking flies, which infest his coat. They're irritating, and even painful, and while his huge claws enable him to have a good scratch, there are always some spots that are just out of reach. To get to them, he needs assistance... a dead tree. That could be the answer. ”***

― **David Attenborough**, *Freshwater*
The *Deinocheirus* attempts to scratch himself with his long arms, but is unable to reach some parts of his body. Spotting a dead tree, *Deinocheirus* heads for it and slams himself upon the tree (scaring off an enantiornithine bird perched on one of the branches in the process), rubbing his back and head on it to get rid of the itching sensations.

***“ And now, he can get back to feeding. But a diet that consists almost entirely of wet vegetation does have one, inevitable consequence. What was food for one becomes fertilizer for many others, and a giant as big as Deinocheirus can produce over 20 tonnes of dung every year. ”***

― **David Attenborough**, *Freshwater*
After having fully scratched himself, the *Deinocheirus* returns to feeding on plants, defecating on the spot, his excrement sinking to the bottom of the swamp, serving as fertilizer for the very plants he feeds on. Swishing his tail in the water to get rid of the fecal matter still on him, the *Deinocheirus* wanders off.

## References

### General

1. ↑ 1.0 1.1 1.2 Molina-Pérez; Larramendi (2016). *Récords y curiosidades de los dinosaurios Terópodos y otros dinosauromorfos*. Barcelona, Spain: Larousse. p. 268
2. ↑ 2.0 2.1 The accuracy and precision of body mass estimation in non-avian dinosaurs
3. ↑ 3.0 3.1 3.2 Hip heights of the gigantic theropod dinosaurs *Deinocheirus mirificus* and *Therizinosaurus cheloniformis*, and implications for museum mounting and paleoecology
4. ↑ 4.0 4.1 4.2 Resolving the long-standing enigmas of a giant ornithomimosaur *Deinocheirus mirificus*
5. ↑ Tyrannosaur feeding traces on *Deinocheirus* (Theropoda: ?Ornithomimosauria) remains from the Nemegt Formation (Late Cretaceous), Mongolia.

### Dr. Darren Naish

1. ↑ *Deinocheirus* lived somewhere cool, and dinosaurs may have been better at temperature control than big mammals.
2. ↑ 2.0 2.1 *Deinocheirus* cannot chew its food, though it does push food to the back of its mouth with its large, muscular tongue.

### Prehistoric Planet

1. ↑ 1.0 1.1 As stated in the official Apple TV+ episode synopsis for Freshwater.
2. ↑ 2.0 2.1 As stated in Freshwater.