Sphenacodontia

Sphenacodontia is a stem-based clade of derived synapsids. It was defined by Amson and Laurin (2011) as "the largest clade that includes Haptodus baylei, Haptodus garnettensis and Sphenacodon ferox, but not Edaphosaurus pogonias". They first appear during the Late Pennsylvanian (Upper Carboniferous) epoch. From the end of the Carboniferous to the end of the Permian, most of them remained large, with only some secondarily becoming small in size.

Tetraceratops insignis ("four-horned face emblem") is an extinct synapsid from the Early Permian that was formerly considered the earliest known representative of Therapsida, a group that includes mammals and their close extinct relatives. It is known from a single skull, discovered in Texas in 1908. According to a 2020 study, it should be classified as a primitive non-therapsid sphenacodont rather than a genuine basal therapsid.

Haptodus is an extinct genus of basal sphenacodonts, a member of the clade that includes therapsids and hence, mammals. It was at least in length. It lived in present-day France during the Early Permian. It was a medium-sized predator, feeding on insects and small vertebrates.

Sphenacodontoidea is a node-based clade that is defined to include the most recent common ancestor of Sphenacodontidae and Therapsida and its descendants (including mammals). Sphenacodontoids are characterised by a number of synapomorphies concerning proportions of the bones of the skull and the teeth.

Pantelosaurus (meaning "complete lizard") is an extinct genus of basal sphenacodonts known from the Early Permian period (Asselian stage) of Saxony, Germany. It contains a single species, Pantelosaurus saxonicus.

thumb|Holotype KUVP 133735

Palaeohatteria is an extinct genus of basal sphenacodonts known from the Early Permian period (Sakmarian stage) of Saxony, Germany. It contains a single species, Palaeohatteria longicaudata.

Hypselohaptodus is a genus of sphenacodont synapsid from the Cisuralian of England. It contains a single species, Hypselohaptodus grandis, and is known only from a single specimen, a partial left maxilla, which is hosted at the Warwick County Museum. It was collected at Kenilworth, Warwickshire, England, from the Kenilworth Sandstone Formation (Warwickshire Group), dating to the earliest Asselian stage of the Cisuralian series, about 299 million years ago.