STL Science Center

STL Science Center

25 May 2020

Long Distance Hugs

We could probably all use some kind of interaction from outside our family these days. While we cannot really pat one another on the back and continue social distancing, there are animals that could have done so. One such animal was the ornithomimosaur Deinocheirus mirificus. Originally, a pair of arms and their shoulders were described in 1970 by Osmólska & Roniewicz, and Deinocheirus was originally thought to be some kind of carnosaur. The description was amended after some time to assign Deinocheirus to the ornithomimosaurs, but new material to even more thoroughly describe the dinosaur was unknown for nearly 50 years. In 2014 (49 years after the initial dig that found Deinocheirus remains) new remains were found in Mongolia (later they were stolen but then returned to the country) from two individuals of the species. At an estimated 11 m and 6.4 t, this was a large and heavy ornithomimosaur of the Late Cretaceous.

The enormous hands and long arms are thought to have been well adapted for digging, which, given the duckbill-like head that seems adapted for water and grass foraging, appears to be at odds with the hypothesized diet. A large number of gastroliths associated with Deinocheirus support a vegetation heavy diet, as the dinosaur would have used these to help break down the fibrous plant matter. It has been reported that fish vertebrae were also discovered along with the gastroliths, meaning that it is likely that Deinocheirus was eating fish as well. Could oversized hands be useful for catching fish? There is a possibility for this as a use, but digging and manipulation of vegetation remains a good hypothesis.

Digging, with large hands, could help efficiently find supplemental dietary items like insects and burrowing lizards; there is no known evidence for this behavior currently. Also unknown is the nesting behavior of these animals. Could hands good at digging make very good nesting mounds? This is also a potential hypothesis. Holding vegetation to crop (or chop) small amounts of food could also be plausible. Defense could also be a plausible explanation for the namesake "horrible hands". Injuries to the holotype digit joints and bitemarks in the coracoids near the shoulder indicate manipulation of the digits (important for dexterous activities noted above) and unsuccessful predation. These predation events are attributed to one of the largest predators on Earth during the Cretaceous, Tarbosaurus bataar.
Adapted by Wiki users from the original at (