16.) Deinocheirus The Deinocheirus was the largest ornithomimosaurian (ostrich dinosaur) to ever exist. The bones were discovered in the Nemegt Formation of Mongolia in 1965. It measured 11 m (36 ft), with an estimated weight of 6.36 t (14,000 lb). Its claws are huge and were probably very useful for digging up food or scaring off attackers!