n.
Any of the various advanced reptiles in the subclass Archosauria ("ruling reptiles"), including all thecodonts, pterosaurs , dinosaurs , birds, and crocodilians.
The first known archosaurs appeared 242227 million years ago during the Triassic Period . All early archosaurs possessed an ankle specialization that aided in upright posture, and most had long hindlegs and short forelimbs. Unlike the teeth of earlier reptiles, which were set in a shallow groove, the teeth of archosaurs were (and are) set in sockets.