Thrinaxodontidae is an extinct

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

cynodont The cynodonts () (clade Cynodontia) are a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya), and extensively diversified after the Permian–Triassic extinction event. Cynodonts had a wide variety ...

s that includes the genera ''

Thrinaxodon ''Thrinaxodon'' is an extinct genus of cynodonts, most commonly regarded by its species ''T. liorhinus'' which lived in what are now South Africa and Antarctica during the Early Triassic. ''Thrinaxodon'' lived just after the Permian–Triassic m ...

'', '' Nanictosaurus'', and '' Nanocynodon'', and possibly ''

Bolotridon ''Bolotridon'' is an extinct genus of epicynodontian cynodont. It was renamed from its original genus designation of ''Tribolodon'' (Harry Govier Seeley, 1895), which was already occupied by a genus of cyprinid fish named in 1883 by Sauvage. The ...

'', '' Novocynodon'' and ''

Platycraniellus ''Platycraniellus'' is an extinct genus of non-mammalian cynodonts. It is known from the Early Triassic ''Lystrosaurus'' Assemblage Zone of the Normandien Formation of South Africa. The type and only species is ''P. elegans''. See also * Lis ...

''. All thrinaxodontids share a bony

secondary palate The secondary palate is an anatomical structure that divides the nasal cavity from the oral cavity in many vertebrates. In human embryology, it refers to that portion of the hard palate that is formed by the growth of the two palatine shelves medi ...

. Thrinaxodontids are basal members of the cynodont

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

Epicynodontia Epicynodontia is a clade of cynodont therapsids that includes most cynodonts, such as galesaurids, thrinaxodontids, and Eucynodontia (including mammals). It was erected as a stem-based taxon by Hopson and Kitching (2001) and defined as the mo ...

. Some studies consider the family a

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

group, representing an

evolutionary grade A grade is a taxon united by a level of morphological or physiological complexity. The term was coined by British biologist Julian Huxley, to contrast with clade, a strictly phylogenetic unit. Definition An evolutionary grade is a group of ...

of basal epicynodonts rather than an actual clade.

References

Prehistoric cynodonts Early Triassic first appearances Early Triassic extinctions Prehistoric therapsid families {{Paleo-Therapsid-stub