Artwork of the dinosaur Struthiomimus. This extinct ostrich-like animal lived in what is now North America towards end of the Late Cretaceous period, some 70 million years ago. Meaning 'ostrich-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.