April 4, 2022 Scott Kraus

Gallimimus is the Largest Ornithomimid Dinosaur

Gallimimus pronounced “Gal-ih-MY-mus”, was a dinosaur from the Ornithomimidae family, which was a genus of theropod dinosaurs that looked like modern day ostriches. It was actually the largest of the Ornithomimids. Its name comes from the Greek words meaning “rooster mimic”, referring to its similarity to a flightless bird. Gallimimmus lived during the late Cretaceous period, about 65-70 million years ago. Although it was a theropod, paleontologists don’t believe it was carnivorous, like most theropods. Its beak was toothless, like a birds, so it was thought to be an omnivore.

Quick Facts

What did Gallimimus look like?

If you were standing on the plains in the warm, humid ecosystem that is now Mongolia during the late Cretaceous, you might see Gallimimus feeding among the tropical foliage. It was a digigrade bipedal omnivore, meaning that it walked on its toes on two feet, eating plants and small aquatic life. It was incredibly long for its size, while only on average 2 meters tall, some specimens have reached 8 meters from snout to tail. Propelled by abnormally large hips and a long femur (hip bone) the Gallimimus would have been similar to a modern day ostrich. Like the ostrich, the Gallimimus could run from predators, and its long legs and beak complete the look.

Physical characteristics of the Gallimimus.

The long physique of the Gallimimus, and in particular the curvature of the neck, similar to a chicken, lead to the name of the Gallimimus. The creature also had an elongated snout, that apparently grew the most during adulthood. To offset the mass of the torso and skull, the Gallimimus had a thick, sinuous tail, used for balance. Its eyes were set on opposite sides of the skull, ensuring that its vision was better at detecting movement around it. It may not have had the binocular vision of an eagle, but that would have been offset by its herd mentality and group numbers.

Uncertainty about Gallimimus

The front arms and the beak of the Gallimimus have caused some debate among paleontologists. The first assumption upon finding Gallimimus remains was that the short, three fingered forelimbs were used for hunting and foraging in the dense undergrowth, then prevalent in the area. Its beak was also thought to be ideally suited, due to thin ribs present on the inside of the beak, to sift the tiny water living creatures, like mollocks, vegetation, insects, etc. making the Gallimimus a omnivore. It is commonly thought now however, that the adaptation was an unused feature of the family of Ornithominidae it belonged to. This is evidenced by the presence of similar structures on known herbivore animals, and casts doubt as to whether the Gallimimus was not an herbivore instead. The classification of diet is still under debate however, until more complete specimens are found.

What did Gallimimus Eat?

The Gallimimus has, at various times, been described as carnivore, omnivore, and herbivore. The original scientists who described it thought it was a carnivore, but in the past decade, or so, the general opinion has vacillated between omnivore and herbivore. In 2001, a beak specimen of Gallimimus, with preserved soft tissue, was shown to have the same kinds of vertical ridges that ducks use to strain plants as well as meat such as mollusks. The environment that Gallimimus lived in also indicates to paleontologists that it was an omnivore since its region would have contained a lot of water. That suggests that the similarity of its beak to a duck’s beak was not just coincidental. Gallimimus has also been suspected to be a herbivore due to the fact that other herbivores have similar qualities to their mouths, namely turtles and Edmontosaurus. On the other hand, if Gallimimus was an omnivore, that would help to explain its long grasping claws, which would be useful for catching and holding prey or digging in the dirt for insects.

How did Gallimimus move?

Gallimimus was bipedal, so it moved along the ground on its two back legs and toes, and it could move fast. We know that Gallimimus was a fast runner because of the similarity of its leg proportions to other fast animals, like ostriches and horses. Its speed would have come in handy for catching prey and fleeing predators.

Predators of Gallimimus

Two predators that Gallimimus had to fear were Saurornithoides and Tarbosaurus. They were both ferocious theropod carnivores that lived in Mongolia during the late Cretaceous period, at the same time that Gallimimus lived. Luckily, Gallimimus was a fast runner which would have been a very helpful defense.

Where did Gallimimus Live?

Gallimimus lived in what is now Mongolia. They probably lived in plains or lowlands so that they could run long distances without being impeded by lots of vegetation. The fossil records also indicate that dinosaurs in the Ornithiminidae family were in Mesic environments, meaning that there was a good supply of water in the area, so Gallimimus had lots of water available to find aquatic organisms to eat.

The Discovery of Gallimimus

Gallimimus was first discovered in the Gobi Desert of Mongolia in August of 1963. It was a Polish-Mongolian expedition led by Professor Zofia Kielan-Jaworowska, who reported it in 1965. In 1972, three other paleontologists named the species “Gallimimus Bullatus”. The “rooster mimic” meaning behind the name came from a similarity in the neural arches between the dinosaur and Galliformes, which is an order of bird more commonly known as game fowl. The holotype specimen is the largest known example of the dinosaur, but several smaller specimens have been found and determined to be juveniles.

The Importance of Gallimimus

The Gallimimus has the distinction of being represented in the popular film Jurassic Park, so you may be more familiar with what it looks like than you thought. The film makers portrayed the Gallimimus grazing in a herd, only to be disrupted by the giant theropod, Tyrannosaurus. However, the evidence isn’t sufficient to state with confidence that Gallimimus did live in herds. Paleontologists don’t have much information about the behavior of Gallimimus, but hopefully that will change as more fossils are discovered.