A cousin of modern crocodiles, Postosuchus was an archosaur - the lineage of reptiles that include the crocodiles, dinosaurs and birds. Reaching lengths of five metres, Postosuchus was the top predator during the Late Triassic in what’s now the southern USA. Since its front limbs were shorter than its hind limbs, there is debate as to whether it walked on two legs or four, but most palaeontologists favour the latter. Its stance, with the legs under the body, would have made it a faster and more efficient runner than a modern crocodile. Most Postosuchus fossils have been found in Texas’ Post quarry, hence the name.