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".[2] They first appear during the Late Pennsylvanian epoch.

Temporal range: Latest Pennsylvanian-Recent, 299.9–0 Ma
Dimetrodon NT2 small.jpg
CG restoration of Dimetrodon homogenes
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Eupelycosauria
Clade: Haptodontiformes
Clade: Sphenacomorpha
Clade: Sphenacodontia
Genera and Clades

Basal Sphenacodontia constitute a transitional evolutionary series from early pelycosaurs to ancestral therapsids (which in turn were the ancestors of more advanced forms and finally the mammals). One might say that the sphenacodontians are proto-therapsids.


The defining characteristics include a thickening of the maxilla visible on its internal surface, above the large front (caniniform) teeth; and the premaxillary teeth being set in deep sockets. All other (sister group and more primitive) synapsid clades have teeth that are set in shallow sockets.


Secodontosaurus, Early Permian

The following taxonomy follows Fröbisch et al. (2011) and Benson (2012) unless otherwise noted.[2][3][4]

Class Synapsida

See alsoEdit


  1. ^ Spindler, F. 2016. Morphological description and taxonomic status of Palaeohatteria and Pantelosaurus (Synapsida: Sphenacodontia). Freiberger Forschungshefte C550(23): 1–57. https://www.researchgate.net/publication/321129043_Morphological_description_and_taxonomic_status_of_Palaeohatteria_and_Pantelosaurus_Synapsida_Sphenacodontia
  2. ^ a b Benson, R.J. (2012). "Interrelationships of basal synapsids: cranial and postcranial morphological partitions suggest different topologies". Journal of Systematic Palaeontology. 10 (4): 601–624. doi:10.1080/14772019.2011.631042.
  3. ^ Jörg Fröbisch, Rainer R. Schoch, Johannes Müller, Thomas Schindler and Dieter Schweiss (2011). "A new basal sphenacodontid synapsid from the Late Carboniferous of the Saar-Nahe Basin, Germany" (PDF). Acta Palaeontologica Polonica. 56 (1): 113–120. doi:10.4202/app.2010.0039.CS1 maint: uses authors parameter (link)
  4. ^ https://pdfs.semanticscholar.org/9c44/ab6ded322debc7895dba871e4b06ea2a36f1.pdf

External linksEdit