Sphenacodontoidea

Sphenacodontoids; Temporal range: Late Carboniferous-Recent, 300–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N
	Fossilized skull of two sphenacodontoids : Clelandina (Therapsida, Gorgonopsidae) and a Dimetrodon (Sphenacodontidae).
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Synapsida
Clade:	Sphenacomorpha
Clade:	Sphenacodontia
Clade:	Pantherapsida
Clade:	Sphenacodontoidea
Clades
	†Sphenacodontidae; Therapsida;

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.

The sphenacodontoids evolved from earlier sphenacodonts such as Haptodus via a number of transitional stages of small, unspecialised pelycosaurs.

Classification[]

The following taxonomy follows Fröbisch et al. (2011) and Benson (2012) unless otherwise noted.^[1]^[2]

Class Synapsida

^ 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)
^ 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. S2CID 84706899.