Sauria is a clade of reptiles that includes all living diapsids, as well as their common ancestor and all its extinct descendants. The ancestral saurian was probably a small lizard-like creature living in the Permian Period. This crown group is diagnosed by a number of details in skull and skeleton, and comprises the two important clades Lepidosauromorpha and Archosauromorpha.
The term "Sauria" has previously been used as a synonym of Lacertilia, a suborder of Squamata that includes all lizards but excludes snakes. This classification is rarely used today because as Sauria so-defined is a paraphyletic group.