ornithomimosaurs

Ornithomimosaurs are a clade of theropod dinosaurs known for their bird-mimic body plan. The name means "bird mimic." They have slender builds, very long legs and necks, small heads, and beaked mouths. Many well-preserved fossils show feathers covering the body. They were bipedal and among the fastest-running dinosaurs, with lightweight skeletons adapted for high-speed locomotion.

Most ornithomosaurs had long arms with three-fingered hands and relatively reduced teeth or were toothless, giving them a beaked look. Their skulls were small, eyes medium in size, and tails were long and stiff. Some early or primitive members retained teeth, such as Pelecanimimus, which indicates diversity in dentition within the group.

Diet and ecology: While precise diets varied, many scientists propose omnivory or herbivory, cropping plants with beaks and using gastroliths to help grind tough vegetation. Fossils and trackways suggest they were fast runners that inhabited open environments, possibly foraging over large areas.

Distribution and time: Ornithomimosaurs are known from North America, Asia, and Europe. The group lived from the Middle Jurassic to the Late Cretaceous, with most fossils dating to the Late Cretaceous.

Notable genera: Ornithomimus, Struthiomimus, Gallimimus, Pelecanimimus, and the unusual Deinocheirus, which has extremely long arms and a robust body.

Classification: They belong to the clade Ornithomimosauria within Theropoda; Ornithomimidae includes most well-known forms. The group remains the subject of ongoing research, with new fossils sometimes reshaping understanding of their relationships, behavior, and ecology.