Poposaurus gracilis

Poposaurus was (surprise!) a poposauroid, living in the Late Triassic of the southwestern United States. Despite looking superficially like a theropod dinosaur, poposaurs were on the crocodile line of archosaurs. Poposaurus seemed to have walked habitually on its hind legs, which is a striking example of convergence, and helps make it resemble the early predatory dinosaurs it shared its habitat with.