10 Facts About Ornithomimus, the "Bird Mimic" Dinosaur

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How Much Do You Know About Ornithomimus?

Julio Lacerda

Ornithomimus, the "bird mimic," was a dinosaur that looked uncannily like an ostrich―and lent its name to an extensive family that stretched across the expanse of late Cretaceous Eurasia and North America. On the following pages, you'll discover 10 fascinating facts about this long-legged speed demon.

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Ornithomimus Looked a Lot Like a Modern Ostrich

Ostrich (Struthio camelus) walking in Palmwag Conservancy, Damaraland, Namibia
Danita Delimont / Getty Images

If you're willing to overlook its gangly arms, Ornithomimus bore a striking resemblance to a modern ostrich, with a small, toothless head, a squat torso, and long hind legs; at three hundred pounds or so for the largest individuals, it even weighed as much as an ostrich. This dinosaur's name, Greek for "bird mimic," alludes to this superficial kinship, though modern birds didn't descent from Ornithomimus, but from small, feathered raptors and dino-birds.

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Ornithomimus Could Sprint at Over 30 MPH

Ornithomimus skeletal remains

Jens Lallensack [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], from Wikimedia Commons 

Ornithomimus not only resembled an ostrich, but it presumably behaved like an ostrich as well, meaning it could hit sustained running speeds of about 30 miles per hour. Since all the evidence points to this dinosaur having been a plant eater (or at the very most an occasional omnivore; see slide #9), it clearly used its blazing speed to escape from predators―such as the numerous raptors and tyrannosaurs that shared its late Cretaceous habitat.

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Ornithomimus Was Endowed With a Larger-Than-Usual Brain

Ornithomimus skull

Jens Lallensack [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], from Wikimedia Commons 

Given its tiny head, the brain of Ornithomimus wasn't very big in absolute terms. However, it was above-average in size compared to the rest of this dinosaur's body, a measure known as encephalization quotient (EQ). The most likely explanation for Ornithomimus' extra grey matter is that this dinosaur needed to maintain its balance at high speeds (not a small matter when you're sprinting at 30 miles per hour!), and may have had slightly enhanced smell, sight and hearing.

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Ornithomimus Was Named by the Famous Paleontologist Othniel C. Marsh

Othniel Marsh

Mathew Brady (1822-1896) or w:en:Levin Corbin Handy (1855–1932) [Public domain], via Wikimedia Commons 

Ornithomimus had the fortune (or misfortune) to be identified in 1890, at a time when dinosaur fossils were being discovered by the thousands, but scientific knowledge had yet to catch up with this wealth of data. Although the famous paleontologist Othniel C. Marsh didn't actually discover the type specimen of Ornithomimus, he did have the honor of naming this dinosaur, after a partial skeleton unearthed in Utah made its way to his study at Yale University.

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There Were Once Over a Dozen Named Species of Ornithomimus

Ornithomimus species
Canadian Museum of Nature

Because Ornithomimus was discovered so early, it quickly attained the status of a "wastebasket taxon": virtually any dinosaur that remotely resembled it was assigned to its genus, resulting, at one point, in 17 different named species. It took decades for this confusion to be sorted out, partly by the invalidation of some species, and partly by the erection of new genera (for example, two Ornithomimus species have since been promoted to their own genera, Archaeornithomimus and Dromiceiomimus).

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Ornithomimus Was a Close Relative of Struthiomimus

Sergio Perez

Although most of the confusion concerning its various species has been sorted out, there's still some disagreement among paleontologists about whether some Ornithomimus specimens should be properly identified as the extremely similar Struthiomimus ("ostrich mimic"). The comparably sized Struthiomimus was virtually identical to Ornithomimus, and shared its North American territory 75 million years ago, but its arms were slightly longer and its grasping hands had slightly stronger fingers.

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Adult Ornithomimus Were Equipped With Proto-Wings

Vladimir Nikolov

It's unclear whether Ornithomimus was covered head to toe with feathers, which only rarely leave fossil imprints. However, we know for a fact that this dinosaur sprouted feathers on its forearms, which (given its 300-pound size) would have been useless for flight, but would certainly have come in handy for mating displays. This raises the possibility that the wings of modern birds evolved primarily as a sexually selected characteristic, and only secondarily as a way to take flight!

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The Diet of Ornithomimus Remains a Mystery

Ornithomimus skull

Wikimedia Commons/Creative Commons 3.0

One of the most mysterious things about Ornithomimus is what it ate. Given its small, toothless jaws, large, wriggling prey would have been out of the question, but then again this dinosaur had long, grasping fingers, which would have been ideal for snatching up small mammals and theropods. The most likely explanation is that Ornithomimus was mostly a plant-eater (using its claws to rope in copious amounts of vegetation), but supplemented its diet with occasional small servings of meat.

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One Species of Ornithomimus Was Much Bigger Than the Other


IJReid [CC BY 4.0 (https://creativecommons.org/licenses/by/4.0)], from Wikimedia Commons 

Today, there are only two named species of Ornithomimus: O. velox (the one named by Othniel C. Marsh in 1890), and O. edmontonicus (named by Charles Sternberg in 1933). Based on a recent analysis of fossil remains, this second species may have been about 20 percent bigger than the type species, with full-grown adults weighing close to 400 pounds. (Still, given the lack of fossils corresponding to different growth stages, it's difficult to make firm judgments about relative size.)

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Ornithomimus Has Lent its Name to an Entire Family of Dinosaurs


GermanOle [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], from Wikimedia Commons 

Ornithomimids―the family of "bird mimics" named after Ornithomimus―have been discovered across North America and Eurasia, with one controversial species (which may or may not have been a true bird mimic) hailing from Australia. All of these dinosaurs shared the same basic body plan, and all of them seem to have pursued the same opportunistic diet (though one early genus, Pelecanimimus, sported over 200 teeth and may have been a devoted meat eater).