Ornithomimidae
Ornithomimids probably acquired most of their calories from plants. Many ornithomimosaurs, including primitive species, have been found with numerous gastroliths in their stomachs, characteristic of herbivores. Henry Fairfield Osborn suggested that the long, sloth-like 'arms' of ornithomimids may have been used to pull down branches on which to feed, an idea supported by further study of their strange, hook-like hands.  Ornithomimids probably acquired most of their calories from plants. Many ornithomimosaurs, including primitive species, have been found with numerous gastroliths in their stomachs, characteristic of herbivores.