Artwork of pair of Struthiomimus. This extinct ostrich-like dinosaur lived in what is now North America towards end of the Late Cretaceous period, some 70 million years ago. Meaning 'ostritch mimic', Struthiomimus. was an Ornithomimid, closely related to Ornithomimus ('bird mimic') and Gallimimus ('chicken mimic') from Mongolia. It had a toothless beak, measured around 4.3 metres (14 feet) in length, and is estimated to have been able to run at speeds in excess of 50km/h (31 mph). It most likely had feathers.