Sphenacodontoidea is a node-based

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

that is defined to include the

most recent common ancestor A most recent common ancestor (MRCA), also known as a last common ancestor (LCA), is the most recent individual from which all organisms of a set are inferred to have descended. The most recent common ancestor of a higher taxon is generally assu ...

of Sphenacodontidae and Therapsida and its descendants (including

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

s). 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'' 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 Pangaea or Pangea ( ) was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia (continent), Siberia during the Carboniferous period ...

in the Late Carboniferous. Later, in

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

, 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 Synapsida is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant rep ...

* Sphenacodontoidea ** Family † Sphenacodontidae **

Therapsida Therapsida is a clade comprising a major group of eupelycosaurian synapsids that includes mammals and their ancestors and close relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including l ...

Phylogeny

Sphenacodontoidea in a

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

modified from Huttenlocker ''et al''. (2021):

References

External links

* {{Taxonbar, from=Q5853182 Transitional fossils Extant Pennsylvanian first appearances

Classification

Phylogeny

See also

References

Further reading

External links