| Sphenacodontoids Temporal range: Late Carboniferous–Middle Permian, 303–0 Ma |
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|---|---|
| Ctenospondylus | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Synapsida |
| (unranked): | Eupelycosauria |
| (unranked): | Sphenacodontia |
| (unranked): | Sphenacodontoidea |
| Genera and Clades | |
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See Taxonomy |
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Sphenacodontoidea is the name given to the clade that includes the most recent common ancestor of the Sphenacodontidae and the Therapsida and their descendants (including mammals). They are defined according to a number of specialised characteristics concerning proportions of the bones of the skull and the teeth.
The Sphenacodontoidea evolved from earlier Sphenacodontia such as Haptodus via a number of transitional stages of small, unspecialised pelycosaurs.