Pylaecephalidae is a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

dicynodont Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivores that typically bore a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, t ...

therapsids that includes ''

Diictodon ''Diictodon'' (meaning "two weasel teeth") is an extinct genus of pylaecephalid dicynodont that lived during the Late Permian period, approximately 255 million years ago. Fossils have been found in the ''Cistecephalus'' Assemblage Zone of the M ...

'', ''

Robertia ''Robertia'' is an extinct genus of small herbivorous dicynodonts from the Middle to Late Permian of South Africa, between 260 and 265 million years ago. It is a monospecific genus, consisting of the type-species ''R. broomiana,'' which was clas ...

'', and '' Prosictodon'' from the

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 ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

. Pylaecephalids were small burrowing dicynodonts with long tusks. The family was first named in 1934 and was redefined in 2009. Diictodontidae and Robertiidae are considered

junior synonym In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...

s of Pylaecephalidae; although ''Pylaecephalus'' itself is considered a junior synonym of ''Diictodon'',Sullivan, C., & Reisz, R. R. (2005)
CRANIAL ANATOMY AND TAXONOMY OF THE LATE PERMIAN DICYNODONT DIICTODON.
Annals of Carnegie Museum, 74(1), 45–75. the name Pylaecephalidae predates these names and therefore takes priority.

Phylogeny

Below is 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 Angielczyk et al. (2021):

References

Prehistoric synapsids of Africa Dicynodontia Permian synapsids Permian first appearances Permian extinctions Prehistoric therapsid families {{anomodont-stub