Archosauria is a clade of reptiles that includes modern birds and crocodilians, as well as their extinct relatives like dinosaurs and pterosaurs. This group is characterized by specific features in their skulls and limbs, which distinguish them from other reptiles. The origin of Archosauria dates back to the late Permian period, around 250 million years ago. They became the dominant terrestrial vertebrates during the Mesozoic era, which is often referred to as the "Age of Reptiles." Their evolutionary adaptations allowed them to thrive in various environments.