Artwork of the dinosaur Gallimimus. This extinct ostrich-like animal lived in what is now Mongolia towards the Late Cretaceous period, some 70 million years ago. Meaning 'chicken mimic', Gallimimus was the largest known Ornithomimid, closely related to Ornithomimus ('bird mimic'). It had a toothless beak, measured around 6 metres (20 feet) in length, and is estimated to have been able to run at a speed of 50km/h (31 mph). It most likely had feathers.