Sauropsida ("lizard faces") is a group of amniotes that includes all existing birds and reptiles as well as their fossil ancestors and other extinct relatives. Large land animals are either in this group or in its sister group, Synapsida, which includes mammals and their fossil relatives. This clade includes the reptiles of Parareptilia and other extinct clades. All living sauropsids are members of the subgroup Diapsida, the Parareptilia clade having died out 200 million years BC in the Late Triassic, likely due to the Triassic-Jurassic Extinction Event. The term originated in 1864 with Thomas Henry Huxley, who grouped birds with reptiles based on fossil evidence.
Sauropsids date back to the Late Carboniferous (Pennsylvanian).