Eupelycosauria is a large clade of animals characterized by the unique shape of their skull, encompassing all mammals and their closest extinct relatives.

Many non-therapsid eupelycosaurs were the dominant land animals from the latest Carboniferous to the end of the Early Permian epoch.

Sphenacodontids, a family of carnivorous eupelycosaurs, included the famous Dimetrodon, which is sometimes mistaken for a dinosaur, and was the largest predator of the period.

They became the succeeding dominant land animals for the rest of the Permian, and in the latter part of the Triassic, descendants of the cynodonts, an advanced group of therapsids, gave rise to the first true mammals.

The following cladogram is modified from Huttenlocker et al. (2021):[10] Caseasauria Varanopidae Ophiacodontidae Edaphosauridae Haptodus Ianthodon Palaeohatteria Pantelosaurus Cutleria Secodontosaurus Cryptovenator Sphenacodon Ctenospondylus Dimetrodon Shashajaia bermani Raranimus Dinocephalia Anomodontia Biarmosuchia Gorgonopsia Therocephalia to Mammaliaformes