Struthiomimidae

Struthiomimidae is a family of theropod dinosaurs within the ornithomimosaurs, a group commonly known as ostrich-mimic dinosaurs. The name derives from the ostrich-like body plan of many members and from Struthiomimus, one of its better-known genera. Struthiomimids are characterized by gracile, toothless beaks, extremely long legs, and an overall lightweight, cursorial build. Their forelimbs were relatively short, with three fingers, and their tails were long and stiff. These traits indicate adaptations for fast running and efficient foraging rather than heavy predation.

The group inhabited the Early to Late Cretaceous and fossils are principally found in North America, with additional records from Asia in some analyses. Struthiomimids were among the most svelte and rapid theropods of their time, and their limb proportions suggest high-speed bipedal locomotion. Estimated body lengths range from roughly 2 to 4 meters, varying by genus and species.

Diet is uncertain; beaks and jaws imply a diet that could include plants, seeds, insects, and possibly small vertebrates, reflecting an omnivorous or opportunistic feeding strategy. The exact taxonomy of Struthiomimidae is debated, with some classifications treating it as a distinct family and others placing its members within Ornithomimidae. Genera commonly associated with Struthiomimidae include Struthiomimus and Dromiceiomimus, among others.

Fossils provide important clues to the diversity and evolution of ornithomimids, highlighting adaptations for speed and dispersion across Late Cretaceous ecosystems.