The hip bones of many dinosaurs evolved in such a way that walking upright on two legs became an efficient way to travel. Dinosaurs that walked in this way developed long legs, which allowed them to walk and run very efficiently. Scientists used to think that they walked in an upright position with their tail dragging on the ground, but we now know that the tail stuck out horizontally to balance the forward-leaning body. These dinosaurs were able to stand upright while grazing.
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