Deinocheiridae is a family of large-bodied ornithomimosaurs -- part of the "ostrich mimic" theropod lineage -- best known for extraordinarily long, robust forelimbs rather than the speed usually associated with their relatives. The type genus Deinocheirus, from the Late Cretaceous of Mongolia, had arms roughly 2.4 meters long tipped with blunt, three-fingered claws, a build so unusual that for decades it was known only from a pair of isolated arms, leaving its full body plan a mystery until more complete skeletons were described. Unlike typical fast-running ornithomimosaurs, deinocheirids were heavily built and not adapted for speed, with skull and gut-content evidence -- including fish scales and stomach stones -- pointing to an omnivorous diet.
The family lived roughly 96 to 70 million years ago and, alongside Deinocheirus, includes Garudimimus and Beishanlong, both from Cretaceous Asia. A tall neural-spine "sail" along Deinocheirus's back and its unusual proportions have made it one of the more visually distinctive theropods once fully described, and its long-mysterious arms remain a well-known example in paleontology of how partial fossils can leave even a genus's basic body plan unresolved for generations.