Sphenacodontia
| Sphenacodontia Temporal range: Late Pennsylvanian-Recent, | |
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| 3D restoration of Dimetrodon grandis, a sphenacodontid | |
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| Restoration of a pair of Alopecognathus angusticeps, a therocephalian therapsid | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Synapsida |
| Clade: | Sphenacomorpha |
| Clade: | Sphenacodontia Romer & Price, 1940 |
| Subgroups | |
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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. The earliest sphenacodontians were small carnivores, though the group also includes large carnivores, such as the famous Dimetrodon (Sphenacodontidae). The group includes Therapsida, the only living subclade of Synapsida (including living mammals), which is most closely related to Sphenacodontidae within Sphenacodontia as part of the subclade Sphenacodontoidea.