These are the ostrich dinosaurs. They had very long legs, thin bodies, and small heads. They also had very long arms with long fingers. There are many different opinions about what types of food Ornithomimids ate. Most had no teeth (although some of the earlier ones did have lots of very small teeth, Pelecanimimus had over 200 teeth in its mouth), only a bird-like beak, making them unable to eat meat. Other scientists point out that there are a number of birds that have no teeth that eat meat. Some scientists think that Ornithomimids ate both plants and meat.
The one thing that all scientists agree on is that the Ornithomimids were the fastest dinosaurs. With long, thin legs (especially the bones in the lower leg), it would be easy to take large steps. Their sleek, thin body would have lowered their weight and made them more streamlined, helping them go faster. Trackways in the Southern United States show footprints of what are thought to be Ornithomimids running at speeds of over 35 km/hour. That was probably not top speed, but even if it was, it was still a lot faster than any human can run.
Ornithomimids are known from Asia, North America, Europe, and Australia. Most are from the Late Cretaceous, but there are a few from the Early Cretaceous. The earlier ones have very small, cone-shaped teeth, but the later forms have no teeth at all. Very good finds, including skulls, have been found recently in Alberta which will add to what we know about these animals. They ranged in size from about 3 meters (Timimus) to about 5 meters (Gallimimus). This group includes Ornithomimus, Struthiomimus, Gallimimus, Timimus, Garudimimus, Dromiceiomimus, Harpymimus, Anserimimus, Pelecanimimus, and Archaeornithomimus.