Speed. Cunning. Intelligence. An Impressive Cretaceous Combination.

Greetings. Ornithomimus is an extinct genus of ornithomimid theropod dinosaurs that thrived during the Late Cretaceous, between 76.5 and 66 million years ago. Ornithomimus was a swift, bipedal dinosaur with fossil evidence indicating that the reptiles were covered in feathers and equipped with a small toothless beak that may indicate an omnivorous diet. The genus had two species: Ornithomimus velox, and Ornithomimus edmontonicus. O. velox was named in 1890 by Othniel Charles Marsh on the basis of fossilized remains originating from the Denver Formation of Colorado. 

Like other ornithomimids, the two species of ornithomimus were characterized by possessing strong feet with three weight-bearing toes, long slender arms, and long necks with birdlike, elongated, toothless, beaked skulls. They were completely bipedal and, on the surface, resembled modern-day ratites. They would have been swift runners thanks to their very long limbs and hollow bones, had large forward-facing eyes, and one of the largest brain sizes, in comparison with the body, of any known species of dinosaur. All the aforementioned physical characteristics are strongly suggestive of an active, cunning, and intelligent predator. Ornithomimus differs from other ornithomimids, such as struthiomimus, in having shorter torsos, long slender forearms, very slender, straight hand and foot claws, and hand bones and fingers of similar lengths. The two species of ornithomimus were somewhat similar in physical dimensions, with the larger O. edmontonicus coming in at approximately 3.8 meters in length, with a postulated weight of about 170 kilograms, with both species being endothermic, or warm-blooded.

Ornithomimus, like many dinosaurs, was once erroneously thought to have been scaly. By 1995 however, several specimens of Ornithomimus had been uncovered that preserved evidence of feathers. In 1995, 2008, and 2009, three O. edmontonicus specimens with evidence of feathers were found (two adults with carbonized traces on the lower arm, indicating the former presence of pennaceous feather shafts, and a juvenile with impressions of feathers, which were about five centimeters in length, in the form of hair-like filaments covering the rump, legs, and neck was also discovered.) A scientific study conducted in 2012 concluded that O. edmontonicus was covered in plumaceous feathers at all growth stages and that only adults had pennaceous wing-like structures, suggesting that wings may have evolved for use during the mating season. 

A fourth feathered specimen of ornithomimus, this time from the lower portion of the Dinosaur Park Formation, was described in October of 2015. It was the first ornithomimus specimen known to have preserved the feathers of its tail. The feathers, though severely crushed and distorted, bore numerous similarities to those of the extant ostrich, both in structure and overall distribution. Skin impressions were also preserved in the same specimen, which indicated that, from mid-thigh to the feet, there was bare skin and that a flap of skin connected the upper thigh to the torso. This latter structure is similar to that found in modern birds, including ostriches, but was positioned higher above the knee in ornithomimus than in today's birds (avian dinosaurs.)

The diet of ornithomimus is still hotly debated by paleontologists. Being theropods, ornithomimids might have been carnivorous, but their body shape was far better suited for a largely omnivorous lifestyle. The two species of ornithomimus likely fed on insects, crustaceans, fruit, leaves, branches, eggs, lizards, and small mammals.

Ornithomimus had legs that seem clearly suited for rapid locomotion, with the tibia being about 20% longer than the femur. Paleontologists have drawn the conclusion, after decades of intense scrutinization of the genus' physical characteristics, that both species of ornithomimus were capable of running up to 70 kilometers per hour. Additionally, the reptiles had large eye sockets, suggesting of a keen visual sense and the possibility that they were nocturnal by nature. 

As with so many of these magnificent creatures, the two species of ornithomimus were extinguished during the Cretaceous/Paleogene extinction event. The genus was native to the Cretaceous forests of what is now North America, so one can imagine them roaming the forests of modern-day Oregon, Colorado, or Washington State. What a wondrous sight that would be.

Thank you for your time and consideration.