Deinocheirus was an Ornithomimid that is know from only from 8 foot long arms. Scaling from the arms of a Gallimimus, Deinocheirus would be 40 feet long and 4 tons. That is, if it is an Ornithomimid. If it was a Therizinosaur, then it would be 30-33 feet long. It lived in late Cretaceous Mongolia. The first picture is of Ornithomimid Deinocheirus, and the second one is of Therizinosaur Deinocheirus.