Archaeornithomimus

Archaeornithomimus was a genus of ornithomimosaurid theropod dinosaur that originated in the Late Cretaceous of Asia about 70 million years ago. In 1923, Roy Chapman Andrews discovered the remains of Archaeornithomimus during an expedition. It was originally called Ornithomimus asiaticus but was later placed in its own genus by Dale Russel in 1972. 

It was described as a medium-sized ornithomimosaur that was about 3.4 m long and weighed between 45 and 91 kg. A dash of hard evidence showed that Archaeornithomimus had feathers, more like those of ratites, and was equipped with a keratinous beak. The hind limbs were robust. It was a long-legged dinosaur that was built for speed to easily escape its predator. It had a long tail that served as a counterweight to aid locomotion. However, there is not much information about its skull, scientists assumed it was toothless and formed a beak like the other dinosaurs in the group. Archaeornithomimus was probably an omnivore that ate plant parts, insects and small vertebrates such as lizards and mammals.

As Archaeornithomimus was from the Iren Dabasu Formation, it had shared its ecosystem with other dinosaurs such as the tyrannosaur Alectrosaurus, Avimimimus, Gigantoraptor, and even the dromaeosaurid Velociraptor.