It's the first Friday of Ornithomimidosaurs September and what better way to end that Friday then with Deinocheirus
In general the diets of Ornithomimosaurs are unknown except for a few genera such as Pelecanimimus where we can get a fairly good idea from fossil evidence. Other Ornithomimosaurs have been interpreted as being herbivores, predators of small vertebrates like primitive mammals, lizards and snakes, to omnivores that ate both plants and flesh to even egg thieves that raided unguarded nests. When only the arms of Deinocheirus were known, the large claws on the ends of the fingers were interpreted by many to be for rending the flesh of any dinosaur that had been unfortunate to have been caught by them, however we now know that large claws are not always killing weapons.
The wider understanding of therizinosaurs gathered during the latter half of the twentieth and early twenty-first centuries is proof that some large clawed theropods were herbivores. This observation coupled with a large concentration of smooth rounded stones discovered near what would have been the digestive area of one of the Deinocheirus specimens, indicating that they may be gastroliths, has been taken as evidence that supports a more herbivorous lifestyle, with the large claws possibly being used to hook around and pull down branches. However, the herbivorous diet theory may not be the only possibility.
With the recovery of the stolen skull, we also know that Deinocheirus had a ‘spoonbill’, upper and lower jaws that widened out to form a rounded spoon-shape. This begs the question, was Deinocheirus similar to modern spoonbill birds that are known to snatch out invertebrates and small fish from water systems. Here the widened bill increases the catch area making it easy to snatch prey from the water. A comparison to the spinosaurs could also be in order. Some genera of spinosaur such as Ichthyovenator and of course Spinosaurus itself are known to have had growths on their backs as well as well-developed and long arms and claws, both features that can now be seen in Deinocheirus. In addition, the possible gastroliths of Deinocheirus could have just as easily have been used to strip off the scales from fish making them easier to digest. It may be that Deinocheirus waited for seasonal rains to swell rivers and water systems which then brought in a greater amount and variety of fish, which they then gorged themselves upon in times of plenty to build up there fat reserves stored in a hump, which they then relied upon to see them through the remainder of the year in leaner times. If true then Deinocheirus may have been in a comparative evolutionary niche as the spinosaurs that were common in earlier in the Cretaceous. Finally one should consider that as a saurischian theropod, Deinocheirus as an ornithomimosaur would have been descended from predatory ancestors and even some earlier ornithomimids such as Pelecanimimus are perceived to have been more predatory in their dietary needs. This is only speculation however, it remains to be seen to just what other surprises Deinocheirus may have in for us.
As one of the larger dinosaurs in its environment Deinocheirus probably only had to worry about other large theropod dinosaurs when fully grown, as late Cretaceous Asia seems to have been dominated by large tyrannosaurs such as Tarbosaurus and Zhuchengtyrannus. Tarbosaurus in particular may have been a particular threat given that a least one of the ribs discovered at the fossil site of the original arms shows tooth marks that were likely caused by a tyrannosaur, with Tarbosaurus also being known from that approximate location. If this was active predation or more imply a case of scavenging however is simply impossible to say. Aside from tyrannosaurs, Deinocheirus likely came into contact with other types of dinosaurs such as hadrosaurs, ceratopsians, dromaeosaurs, oviraptorids, therizinosaurs, pachycephalosaurs as well as the occasional titanosaur, all while early birds and pterosaurs flew on overhead.
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