Sphenacodontoidea

The sphenacodontoids evolved from earlier sphenacodonts such as Haptodus and Ianthodon via a number of transitional stages of small, 1-10 kg, faunivore animals. The possible common ancestor of sphenacodontids and therapsids was a carnivorous synapsid that reached moderate or large size and more closely resembled the land-dominant Early Permian sphenacodontids than the small Haptodus. The first predators among Sphenacodontoidea, like Shashajaia, appeared in the tropical western part of Pangea in the Late Carboniferous. Later, in Permian, sphenacodontoids gave rise to the dominant terrestrial carnivores in both sphenacodontid and therapsid groups.

Classification

The following taxonomy follows Fröbisch et al. (2011) and Benson (2012) unless otherwise noted.

Class Synapsida

• Sphenacodontoidea
  • Family †Sphenacodontidae
  • Therapsida

Phylogeny

Sphenacodontoidea in a cladogram modified from Huttenlocker et al. (2021):