Prestosuchus

Prestosuchus is an extinct genus of pseudosuchian in the family Prestosuchidae. Its close relatives include Saurosuchus and Postosuchus.

Description
Like other related prestosuchids, Prestosuchus had a deep skull and serrated teeth. Prestosuchus lived during the Late Triassic in what is now Brazil. It reached lengths of nearly 5 metres. While it resembled a dinosaur in having a large body and upright posture it was actually a rauisuchian archosaur more closely related to modern crocodilians.

Prestosuchus walked on four legs like crocodilians, but unlike crocodilians it had an upright semi-erect stance with limb bones placed below the hips. In 2013, a study of the structure of its hind limb bones inferred that Prestosuchus chiriquensis had 13 leg muscle groups in common with both crocodilians and birds (which together make up the two living groups of archosaurs) but only two muscle groups in common with only crocodilians, indicating that the musculature of Prestosuchus better represents a basal ("primitive") condition for archosaurs than it does a derived condition for crocodile-line or pseudosuchian archosaurs. The leg musculature of Prestosuchus was also compared to that of Poposaurus, a Triassic pseudosuchians that walked on two legs. While the strongest leg muscles of Poposaurus are thought to drive the forward and backward motion of the leg necessary for bipedal movement, the strongest leg muscles of Prestosuchus were responsible for the rotation of the limb, which is an indication of quadrupedal movement.