Like other ornithomimids, species of "Ornithomimus" are characterized by feet with three weight-bearing toes, long slender arms, and long necks with birdlike, elongated, toothless, beaked skulls. They were bipedal and superficially resembled an ostrich. They would have been swift runners. They had very long limbs, hollow bones, and large brains and eyes. The brains of ornithomimids in general were large for non-avialan dinosaurs, but this may not necessarily be a sign of greater intelligence; some paleontologists think that the enlarged portions of the brain were dedicated to kinesthetic coordination. The bones of the hands are remarkably sloth-like in appearance, which led Henry Fairfield Osborn to suggest that they were used to hook branches during feeding.