Sauria

Sauria is the clade of diapsids containing the most recent common ancestor of Archosauria (which includes crocodilians and birds) and Lepidosauria (which includes squamates and the tuatara), and all its descendants. Since most molecular phylogenies recover turtles as more closely related to archosaurs than to lepidosaurs as part of Archelosauria, Sauria can be considered the crown group of diapsids, or reptiles in general. Depending on the systematics, Sauria includes all modern reptiles or most of them (including birds, a type of archosaur) as well as various extinct groups.

Archelosauria is a clade grouping turtles and archosaurs (birds and crocodilians) and their closest relatives, to the exclusion of lepidosaurs (the clade containing lizards, snakes and the tuatara). Most phylogenetic analyses based on molecular data (e.g. DNA and proteins) have supported a sister-group relationship between turtles and archosaurs. On the other hand, Archelosauria had not been historically supported by most morphological analyses, which have instead found turtles to either be descendants of parareptiles, early-diverging diapsids outside of Sauria, or close relatives of lepidosau

Sinosaurosphargis is an extinct genus of basal marine saurosphargid reptile known from the Middle Triassic Guanling Formation of Yunnan and Guizhou Provinces, southwestern China. It contains a single species, Sinosaurosphargis yunguiensis. thumb|Life reconstruction of Sinosaurophargis yunguiensis

Ankylopoda was a proposed clade that hypothetically contains turtles and lepidosaurs (tuatara, lizards and snakes) and their fossil relatives. This clade was historically supported based on microRNA analysis as well as some morphological cladistic analyses. However, it was strongly contradicted by molecular evidence which supports Archelosauria (the grouping of turtles and archosaurs), as well as some morphological analyses.