Creature Feature 14

Hello, fans! I hope you have all had a great weekend! This week's Creature Feature will look at Ornithomimus velox.

Ornithomimus velox model - feather texture still work-in-progress.

Ornithomimus velox was a medium-sized theropod dinosaur, somewhat resembling a modern ratite. It was likely rather swift given its large, muscular hindlimbs, and had a small, keratinized beak. While the specimens attributed to O.velox are rather fragmentary and thus hard to evaluate, its sister species O. edmontonicus is known from several extremely well-preserved specimens which allows some degree of inference on the overall biology of O. velox given their close relation.

There have been several specimens of a second species in this genus (O. edmontonicus) found with carbonized traces of feathers, and a description in 2012 concluded that this species retained plumaceous feathers throughout its life, though it only had pennaceous ('wing') feathers at maturity - suggesting that such features may have played a role in mating displays (Zelenitsky et al., 2012). However, others have disagreed on the presence of pennaceous feathers, based on the fact that the feathers like those on the wings of modern cassowaries would leave similar traces (Foth et al., 2014).

Another new feathered specimen of Ornithomimus was described in 2015. This specimen had very similar feather structure and distribution as that found in modern ostriches. Furthermore, the specimen included preserved skin from the hindlimbs, which showed scaleless skin from the mid-thigh to the feet, and a large flap of skin connecting the upper thigh to the torso. Modern birds also share this flap of skin, though in Ornithomimus it was positioned higher from the knee (Van Deer Reest et al., 2016).

The true diet of Ornithomimus and other Ornithomimosaurs is still a subject of debate. This is partially due to their endentulous jaws, which prevent the possibility of inferring diet from tooth structure (you can't analyze a feature if the feature isn't there!). Some authors have suggested that dinosaurs such as Ornithomimus were suspension feeders, using their beak to strain out food from sediments in aqueous environments, somewhat like modern anseriform birds (Norell et al., 2001). However, further analysis of the structure of the beak in Gallimimus suggests a structure more in line with that found in herbivorous chelonians and hadrosaurs, which may suggest a diet consisting of high-fiber plants (Barrett, 2005). On the other hand, there are differences in preserved beaks of Ornithomimus and Struthiomimus when compared to Gallimimus, which does suggest some degree of ecological and dietary divergence from that of Gallimimus (Kobayashi and Lü, 2003). Overall, there is still a large degree of uncertainty as to the actual diet of Ornithomimosaurs in general, though an exclusively carnivorous diet is considered unlikely (Barrett, 2005).

Well, I hope this has given you a bit more information on the rather enigmatic yet very cool theropod known as Ornithomimus!

Acknowledgements:
Zelenitsky, D. K; Therrien, F.; Erickson, G. M.; Debuhr, C. L.; Kobayashi, Y.; Eberth, D. A.; Hadfield, F. 2012. Feathered Non-Avian Dinosaurs from North America Provide Insight into Wing Origins. Science 338 (6106): 510-514.
Foth, Christian; Tischlinger, Helmut; Rauhut, Oliver W. M. 2014. New Specimen of Archaeopteryx provides insights into the evolution of pennaceous feathers. Nature 511 (7507): 79-82.
Van Der Reest, Aaron J.; Wolfe, Alexander P.; Currie, Philip J. 2016. A densely feathered ornithomimid (Dinosauria: Theropoda) from the Upper Cretaceous Dinosaur Park Formation, Alberta, Canada. Cretaceous Research 58: 108.
Norell, M. A.; Makovicky, P. J.; Currie, P. J. 2001. The beaks of ostrich dinosaurs. Nature 412: 873-874.
Barrett, P. M. 2005. The Diet Of Ostrich Dinosaurs (Theropoda: Ornithomimosauria). Palaeontology 48 (2): 347-358.

Kobayashi, Y.; Lü, Jun-Chang. 2003. A new ornithomimid dinosaur with gregareous habits from the Late Cretaceous of China. Acta Palaeontologica Polonica 48: 235-259.