Ornithomimus

Ornithomimus, which means "bird mimic," was a type of dinosaur that lived during the Late Cretaceous period in what is now western North America. This dinosaur was known for being fast and walking on two legs. It had feathers and a small beak without teeth, which suggests it might have eaten both plants and small animals.

The first species of Ornithomimus, called Ornithomimus velox, was discovered and named in 1890 by Othniel Charles Marsh. It was based on a foot and part of a hand found in Colorado. Since then, scientists have named many other species, but most of them are now thought to belong to different dinosaur groups. The most well-known species today is Ornithomimus edmontonicus, found in Alberta in Canada. Many complete skeletons of this species have been found in the Horseshoe Canyon Formation. Sometimes, other species found in different rock layers are also grouped with Ornithomimus, such as Ornithomimus samueli, though they might actually belong to closely related dinosaurs.

History of discovery

The history of naming and classifying Ornithomimus has been complex. The type species, Ornithomimus velox, was first named by O.C. Marsh in 1890. It was based on partial leg and arm bones found in Colorado. The name "Ornithomimus" means "bird mimic," referring to its bird-like appearance. Marsh also named two other species at the same time, but these are now understood to belong to different dinosaurs.

Over the years, many new species were named and later reassigned. In 1933, Charles Mortram Sternberg named the species Ornithomimus edmontonicus based on a nearly complete skeleton from Alberta. In the 1970s, Dale Russell studied these dinosaurs and created two new genera: Archaeornithomimus and Dromiceiomimus, reassigning several species to them. Later research has suggested that some of these species might actually belong to Ornithomimus, particularly Dromiceiomimus, which is often considered the same as Ornithomimus edmontonicus.

Description

Ornithomimus was a fast-moving dinosaur that walked on two legs. It had long, slender arms and a neck that looked like a bird's, with a beak that had no teeth. Its feet had three main toes that helped it run quickly. Ornithomimus had large brains and eyes.

Scientists used to think Ornithomimus had scaly skin like a lizard. But later discoveries showed that it actually had feathers. Some fossils showed feathers on the arms and body, looking like the feathers of modern birds such as ostriches. These feathers might have been used for showing off to mates rather than for flying. The skin on its lower legs and feet had no feathers, and there was a flap of skin connecting the thigh to the body, similar to what birds have today.

Classification

In 1890, a scientist named Marsh placed Ornithomimus in a group called Ornithomimosauria, and many people still use this today. Newer studies using special methods suggest that Ornithomimus was an advanced type within its family. However, these newer studies have only looked at one kind of Ornithomimus, called O. edmontonicus. We still do not know exactly how O. edmontonicus, O. velox, and another kind called O. sedens are related to each other.

Paleobiology

The diet of Ornithomimus is still debated. While it was a type of meat-eating dinosaur, its body shape suggests it might have also eaten a mix of plants and small animals like insects, crustaceans, fruit, leaves, and small mammals.

Ornithomimus had long legs made for fast running, with the lower leg bone being about 20% longer than the upper leg bone. Its large eye sockets suggest it had good vision and might have been active during the night. A study of its foot bones did not find any signs of stress fractures.