Name means: Bird Mimic
Species: edmonticus, velox
Range: Late Cretaceous (Maastrichtian, 76-65 MYA) from Canada (Alberta, Saskatchewan), United States ranging from Montana to Texas, Colorado to Utah
Size estimate: 7-12 ft length, 250-400 lbs
Discovery: Othniel Charles Marsh, 1890
Classification: dinosauria, saurischia, therapoda, coelurosauria, ornithomimidae
Though not as closely related to birds as Deinonychus or Troodon, Ornithomimus and its relatives probably lived a more recognizably birdlike lifestyle. Their resemblance to modern ostriches and emus likely indicates similar behavior. Ornithomimus is therefore yet another example of convergent evolution. Fossils which preserved impressions of soft tissue show that they had feathers. Even the flesh around their legs had a similar shape to their modern cousins. A featherless flap of skin attached the thigh to the animal’s flanks, just like living ostriches. These fossils also show that as Ornithomimus reached adulthood, it grew a fringe of feathers along its arms. The fringe may have played a role in mating displays, though it may also have helped insulate eggs.
Ornithomimus lacked teeth, which makes its diet a mystery. Many scientists accept that it had an omnivorous diet, but as yet none of the available evidence leads to anything specific. Its arms and claws probably helped it gather food, but their shape could work for a number of different tasks. The claws had a slight curve, and somewhat resembled a sloth’s claws. They could have been used for hooking branches to make the leaves easier to reach. They could also rake through termite mounds, dig for grubs, or pull up tubers.
Whatever its diet, Ornithomimus ranked among the fastest dinosaurs. Short thighs, long shins, and long tarsals usually indicate a running specialization. The tarsals are located between the toes and the shin, and technically count as part of the foot. The legs of the Brachiosaurus nearby have the opposite construction. A giant like Brachiosaurus needed stability more than speed. Ornithomimus on the other hand depended on speed to escape predators. Estimates for its tops speed range between 35 and 40 miles per hour, comparable to an ostrich. Its long tail may have made it more maneuverable than an ostrich as well.