The Upper Cretaceous Nemegt Formation of Mongolia is rich in well-preserved dinosaurs and Omithomimosauria is one of the most common taxa in the formation. Three ornithomimosaur taxa, Anserimimus planinychus, Deinocheirus mirificus, and Gallirnimus bullaws, have been discovered from the formation so far. However, the recently discovered specimens suggest there is even greater morphological variation of ornithomimosaurs in the Nemegt Formation than are presently recognized. This study focuses on the structures of manual elements among Nemegt ornithomimosaurs and reveals their remarkable diversity. The manual structures of seven individuals, including aforementioned three known taxa and four new individuals, are morphologically distinct from each other. Numerical analyses on metacarpals, phalanges, and unguals also support high morphological diversity of the Nemegt ornithomimosaurs. The large diversity of manual morphology may be related to large variety of palaeoecological niches were prevailed in the Nemegt ecosystem.
