''Hazhenia'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

therocephalia Therocephalia is an extinct suborder of eutheriodont therapsids (mammals and their close relatives) from the Permian and Triassic. The therocephalians ("beast-heads") are named after their large skulls, which, along with the structure of their te ...

therapsid Therapsida is a major group of eupelycosaurian synapsids that includes mammals, their ancestors and relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more ...

s from the

Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is a un ...

of China, of which ''Hazhenia concava'' is the only species. ''Hazhenia'' was named in 1981 from the Heshanggou Formation in the

Ordos Desert The Ordos Desert () is a desert/steppe region in Northwest China, administrated under the prefecture of Ordos City in the Inner Mongolian Autonomous Region (centered ca. ). It extends over an area of approximately , and comprises two sub-dese ...

Inner Mongolia Inner Mongolia, officially the Inner Mongolia Autonomous Region, is an autonomous region of the People's Republic of China. Its border includes most of the length of China's border with the country of Mongolia. Inner Mongolia also accounts for a ...

. It lived during the

Olenekian In the geologic timescale, the Olenekian is an age in the Early Triassic epoch; in chronostratigraphy, it is a stage in the Lower Triassic series. It spans the time between Ma and Ma (million years ago). The Olenekian is sometimes divided into ...

Age of the Early Triassic, about 247 million years ago. ''Hazhenia'' belongs to a group of therocephalians called

Baurioidea Baurioidea is a superfamily of therocephalian therapsids. It includes advanced therocephalians such as ''Regisaurus'' and ''Bauria''. The superfamily was named by South African paleontologist Robert Broom in 1911. Bauriamorpha, named by D. M. ...

and possesses many mammal-like features such as cusped teeth and a

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 ...

, both of which evolved independently in baurioids. Within Baurioidea it is most closely related to the genus '' Ordosiodon'', which is also known from Inner Mongolia but comes from the slightly younger

Ermaying Formation The Ermaying Formation is a sedimentary succession of Anisian (Middle Triassic) age. It is found in the Shaanxi Province of China. It is composed of an up to 600 m thick sequence of mudstone and sandstone. It is famous for its fossils of tetrapods. ...

. Both genera were once placed in the family Ordosiidae, but as the name is preoccupied by a family of Cambrian trilobites, it is no longer valid. ''Hazhenia'' is known from a single skull that was discovered by a group from the

Institute of Vertebrate Paleontology and Paleoanthropology The Institute of Vertebrate Paleontology and Paleoanthropology (IVPP; ) of China is a research institution and collections repository for fossils, including many dinosaur and pterosaur specimens (many from the Yixian Formation). As its name suggest ...

in 1977, a year after the discovery of the first ''Ordosiodon'' remains. Both were initially classified as members of Scaloposauria, a group of small-sized therocephalians now regarded as 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 ...

assemblage of basal baurioids. A

phylogenetic analysis In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

of therocephalians published in 2014 found ''Hazhenia'' and ''Ordosiodon'' to be each other's closest relatives, and placed both in a

derived Derive may refer to: * Derive (computer algebra system), a commercial system made by Texas Instruments * ''Dérive'' (magazine), an Austrian science magazine on urbanism *Dérive, a psychogeographical concept See also * *Derivation (disambiguatio ...

position within Baurioidea, close to the family

Bauriidae Bauriidae is an extinct family of therocephalian therapsids. Bauriids were the latest-surviving group of therocephalians after the Permian–Triassic extinction event, going extinct in the Middle Triassic. They are among the most advanced euther ...

. Below is a

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

from that analysis:

References

Bauriids Triassic synapsids of Asia Early Triassic synapsids Fossil taxa described in 1981 Therocephalia genera {{paleo-therapsid-stub