Two new specimens of Deinocheirus mirificus, one of the most mysterious dinosaurs known only from two gigantic arms for almost 50 years, are described for the first time in the international journal Nature.
The nearly complete skeletons have been pieced together from a collection of fossils unearthed in Mongolia, along with the recovery of a skull and hand that had been poached and sold to private collectors.
Analyses of the skeletons indicate that Deinocheirusis was the largest member of the ornithomimosaurs, a group of dinosaurs which bore a superficial resemblance to modern ostriches.
One of the specimens had a predicted body length of 11 metres and an estimated body weight of 6,358 kg.
Broad hips and large feet indicate that Deinocheirus was a slow mover.
Deinocheirus seems to have been well-suited to river system habitats. A duck-like bill may have helped it to forage for food at the bottom of streams and blunt, flattened bones under their claws may have prevented it from sinking on wet ground.
Fish remains were found among what seems to be stomach contents but the Deinocheirus skeletons also have features associated with plant eating.
The results of the reconstruction are reported by Yuong-Nam Lee of the Korea Institute of Geoscience and Mineral Resources and colleagues.
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