April 4, 2022 Scott Kraus

As Tall As T-Rex – With Freddy Krueger Forearms

“Terrible Hand” is an appropriate name for this prehistoric Theropod dinosaur that exhibited massive arms according to deduction of its fossilized and minimal bony remains.  Named Deinocheirus, pronounced DYE-no-KYE-rus, is a genus of dinosaur that lived on Earth during the Late Cretaceous Period.  The last indications of its physical life are to date found in southern Mongolia.  The binomial name is Deinocheirus mirificus.

Quick Facts

About Deinocheirus

Scientists are able to reconstruct the most well-preserved bone specimens, into functional arms almost thirteen feet long.  Scientists use a Theropod clade and suborder based formula to determine the probability of the size of Deinocheirus based upon the same body parts.  Specifically, scientists proposed that they could estimate height at the hip of Deinocheirus by using the information they do have—the scapula (shoulder blade).

Through the study of already known—and much more complete Theropod skeletal specimens—scientists determined that hip-height is calculable by scapula size, and have proposed that Deinocheirus could have been at least  11–12 feet tall at the hip.  This would make Deinocheirus the tallest of its contemporary predators (think Tyrannosaurus rex, which could have been a larger dinosaur species, or a smaller one.  Deinocheirus may or may not have been as fierce as T. rex.  However, the contrastable long arms and long, clawed hands of Deinocheirus make one wonder.  See, “What did Deinocheirus Eat?” below.

What Did Deinocheirus Look Like?

Deinocheirus was a Theropod and as such likely a ferocious seeming example, standing thirteen feet at the hip.  That meant that when this prehistoric creature stood up tall on its legs to look about, it could have towered over the landscape at more than twenty-four feet tall.  It is estimated that this dinosaur could have been all the size of Tyrannosaurus rex.  However, the two genera did not necessarily operate in the same way in order to survive.

Where some scientists attribute the large clawed hands as effective weapons of aggression against prey, others attribute the same claws to the ability of most effectively stripping trees for their vegetation.  At least one scientist takes the foliage theory further by positing that Deinocheirus was in fact like a sloth, or at least used its forearms as a sloth would.  He goes on to say that in addition to vegetation, Deinocheirus probably routinely made use of any high-protein finds en route, such as birds’ eggs or any small animals it could catch with its hands.

What Did Deinocheirus Eat?

Deinocheirus is believed to have been an omnivore, meaning that likely this animal ate plant material in addition to meat.  Initially it was thought that Deinocheirus primarily took advantage of weaker—or weakened—prey or dead carcasses.  Its claws were thought to be terrible weapons capable of gutting most any adversary, and definitely any prone food source.  However, as time progresses—and until more solid information to the contrary can be found—most scientists now lean toward a diet of least resistance for Deinocheirus.  Profligate period flora this genus would have frequented are flowering plants, figs, magnolias and conifers.

Any terrestrial fauna that was more prone than Deinocheirus—and smaller—could have been fair enough game.  Especially if Deinocheirus did forage the bush like a sloth as scientists propose, then eggs were probably a healthy source of protein nutrients for the large dinosaur.  Insects gained presence in during the Cretaceous Period and were likely a significant diet source, including ants, termites and moth—especially larvae.  The tops of trees were most likely to be scavenged by Deinocheirus, due to its height.  It has been suggested that Deinocheirus used its long-reaching neck and long arms to reach the highest possible distance, while its claws were utilized to scrape or pull foliage off of main limbs or trunks.  Even though Deinocheirus is thought to have coexisted with other omnivorous and herbivorous dinosaurs, this genus would have naturally taken advantage of its most accessible points, while the other genera primarily scavenged their own, lower-lying areas.

How Did Deinocheirus Move?

Deinocheirus was primarily a bipedal Theropod that could move quickly when necessary, usually due to predation by other more carnivorous dinosaur species.  Deinocheirus was powerfully built and had good defensive arms with claws; however, this species probably usually moved casually, feeding on non-resistant resources and socializing or moving according to climate and foraging opportunity.

Where Did Deinocheirus Live?

Deinocheirus lived during the Early Maastrichtian Era, the era at the end of which there were the mass extinctions known as the Cretaceous—Paleogene extinction event and the Cretaceous–Tertiary extinction event.  After the latter event, non-avian dinosaurs, plesiosaurs, mosasaurs and many others animal species became extinct.

The Discovery of Deinocheirus

Deinocheirus was found in 1965 during an expedition to Gobi, Mongolia by Professor Zofia Kielan-Jaworowska.  The expeditioners were were at the Altan Ula III site.  Halzka Osmolska and Ewa Roniewicz named Deinocheirus in 1970.  The only named species is Deinocheirus mirificus.

The remains of Deinocheirus consist of the well-preserved arms bones, in addition to a complete shoulder girdle, three central vertebrae, five ribs and two of the supporting neck bones (ceratobranchialia).  The ceratoranchialia are significant in adding to the estimation of total size.

In what was is sometimes known as the Nemegt Formation, Deinocheirus was buried in a layer of sediment that eventually compressed to approximately four inches in thickness and formed about 80—71 million years ago.  Also known as the Barun Goyot Formation, it is representative of a large area of the Gobi Desert basin in the Ömnögovi Province of Mongolia.  The formation now serves as a natural protection for its neighboring land of sand dunes (the Aeolian dunes), which were created by the wind-blown rocks over time.  In this area one can find the preserved prehistoric fossilized remains of such creatures as turtles, crocodiles, many dinosaur species, birds and fish.

Deinocheirus—What Big CLAWS You Have!

The well-preserved claws of Deinocheirus were very long, at eight inches, and apparently very stout as part of the most well-preserved remains.  It would not be too unreasonable to maintain that these could have been utilized in a more predatory fashion, in addition to simple defense and foraging.  However, scientists today seem to be inclined toward the latter, even suggesting that Deinocheirus was built to be a nimble climbing creature—even more like the sloth than previously supposed.  No evidence exists today that can fully support this claim of climbing ability.

It will take the discovery of more well-preserved Deinocheirus remains to answer positively the ornithomimosaurid nature of the genus.  Some paleontologists will spend their lives dedicated to this discovery, and it may not be long before these questions are answered, as each day scientists learn more about Deinocheirus.