April 4, 2022 Scott Kraus

Ornithomimus was an Ostrich-Like Omnivore

Ornithomimus (pronounced Or-nith-owe-mim-uss), was a theropod belonging to the ornithomimid family and lived during the Late Cretaceous Period about 70 million years ago, in what is now North America.

Ornithomimus meaning “Bird Mimic” when translated from Greek, which is in reference to its bird-like feet, has given its name to a whole family of similar dinosaurs; the Ornithomimids including Struthiomimus and Gallimimus, the latter of which Ornithomimus was closely related to.

Quick Facts

What did Ornithomimus Look Like?

Ornithomimus was a relatively small dinosaur who looked rather like a modern-day ostrich with the exception of its long tail that it would have held off the ground. This dinosaur had large eyes and a small elongated toothless beak on a small head with a long neck. It had short arms, with each hand having long three-clawed fingers, and long slender legs with three weight-bearing clawed toes on each bird-like foot. Half of Ornithomimus length would have come from its neck and tail and it may have had hair like feathers, particularly as a juvenile though no evidence of this has been found.

Because only partial skeleton remains have been found for Ornithomimus and the three recognized species remains vary in size palaeontologists are unsure how large Ornithomimus really was and estimated vary between 3.5-6 meters long, 1.8-2.4 meters tall and weighing 170-350 kg.

Physical Attributes of Ornithomimus

Ornithomimus had a large brain and this is thought to mean that it had one of the highest intelligence levels of all dinosaurs as with other theropods, however not all palaeontologists agree; some think that the enlarged parts of the brain were dedicated to kinesthetic coordination – The awareness of body movement and the sequence that must be followed from brain to joints and muscles to get the dinosaur moving.

Due to the large eye sockets palaeontologists think that Ornithomimus would have had good eyesight, the large size also suggesting a possibility that this dinosaur was nocturnal, it also had hollow bones to help keep its weight down so that it was able to move fast.

What did Ornithomimus Eat?

As a dinosaur belonging to the theropods it’s possible that Ornithomimus was a carnivore, but due to its body shape it is thought that it would have been more suited to a partly, if not largely, herbivorous lifestyle with palaeontologists settling on an omnivorous lifestyle.

It is thought that it would have lived off a varied diet of insects, land-based crustaceans such as woodlice, eggs, fruit, plants and leaves, seeds and berries as well as the meat from small reptiles and small primitive mammals.

How did Ornithomimus Move?

Ornithomimus was a bipedal dinosaur meaning it walked on two-legs. Palaeontologists think that Ornithomimus would have been a quick runner being fast and agile with its legs clearly suited for rapid movement, the tibia being approximately 20% longer than the femur.

Its long tail would have acted as a stabilizer during fast turns giving it a counterbalance and it is estimated that Ornithomimus would have been able to run up to 70 kph making it the fastest dinosaur to live in its local environment. Ornithomimus would have used its speed to survive having no other defense mechanisms or weapons on its body and it is thought would have stampeded in herds to get away from predators.

Where did Ornithomimus Live?

About 70 million years ago during the Late Cretaceous period Ornithomimus would have been widespread roaming the swamps and forests of what is now known as North America from the Eastern United States including Arizona, Colorado, Montana to Canada.

Its contemporaries would have been Albertosaurus, Parasaurolophus, Kritosaurus, Nanotyrannus and Euoplocephalus. Palaeontologists have analyzed Ornithomimus sceleral rings (rings of bone found in the eye) and found that this dinosaur was likely to have lived a cathemeral lifestyle being active for short periods of time during the day and night.

The Discovery of Ornithomimus

The classification of Ornithomimus, as well as the classification of ornithomimids in general has been complicated with this dinosaur having had one of the most complicated taxonomic histories to date, that still continues to cause much confusion today.

This confusion stems from ornithomimid being one of the first discovered with Ornithomimus and Struthiomimus both being used as a waste basket taxon to store any remains remotely resembling or attributed to these two genus often resulting in a new species being created.

At one time there was thought to be a total of 18 different species of Ornithomimus but the majority of these were either found to be the same as the type species, reassigned a new genus or upon further examination shown to be not directly related to Ornithomimus at all leaving the three valid and recognized species of today; the type species O. velox, the holotype O. edmontinicus and O. sedens.

The first remains for Ornithomimus were found in June 1889 by George Lyman Cannon in Denver, Colorado in the Maastrichtian Denver Formation when a partial forelimb and a partial hind-limb were discovered. This became the type species given the name of O. velox by Othniel Marsh in 1890 with further remains discovered in Wyoming at the Ferris Formation.

O. sedens was named in 1891 by Marsh after partial remains were discovered in Wyoming in the Lance Formation, one year after the description of O. velox was released. Since then a complete specimen from Montana as well as some fragments from Alberta have been recovered.

In 1933 Charles Sternberg named the species O. edmontonicus from a nearly complete skeleton found in Alberta, Canada at the Horseshoe Canyon Formation. It is this species that has the best fossil remains coming from several individuals.

The Importance of Ornithomimus

Ornithomimus is important because it was one of the first dinosaur genus to be created and was used as a reference point to group other similar dinosaurs. It is hoped that in the future, with more fossil finds, and further research and analysis that the final, and true, taxidermy for Ornithomimus and the subsequent species will be discovered and agreed upon perhaps with more valid species joining Ornithomimus or with O velox and O edmontonicus discovered to be the same species.