Largest ostrich dinosaur

The largest species of ostrich dinosaur or ornithomimosaur (named after their superficial outward similarity to an ostrich) was Deinocheirus mirificus. Living approximately 71–69 million years ago during the late Cretaceous in what is today Mongolia, it is currently known from three specimens, the largest of which measures up to 11 m in length and weighs an estimated 6.36 tonnes.

Just like ostriches, ornithomimosaurs were bipedal and very fleet-footed. They had long slender necks, their beaks were usually (although not always) toothless, and their eyes were large in proportion to the size of their skulls. Moreover, their skin was feathered rather than scaly, so in life they would certainly have looked surprisingly ostrich-like.