''Sintocephalus'' is an extinct genus of

dicynodont Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivorous animals with a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, typicall ...

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 ...

from the

Late Permian Late may refer to: * LATE, an acronym which could stand for: ** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia ** Local-authority trading enterprise, a New Zealand business law ** Local average treatment effect, ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

. Fossils are known from the ''Cistecephalus'' Assemblage Zone of the

Beaufort Group The Beaufort Group is the third of the main subdivisions of the Karoo Supergroup in South Africa. It is composed of a lower Adelaide Subgroup and an upper Tarkastad Subgroup. It follows conformably after the Ecca Group and unconformably underlie ...

. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

of ''Sintocephalus'', ''S. alticeps'', was first named in 1913 as a species of ''

Dicynodon ''Dicynodon'' ("two dog-teeth") is a genus of dicynodont therapsid that flourished during the Upper Permian period. Like all dicynodonts, it was herbivorous animal. This reptile was toothless, except for prominent tusks, hence the name. It probab ...

''. The genus was erected in 1934, but in subsequent years its species were often regarded as members of other dicynodont genera.

Description

Compared to other dicynodonts, ''Sintocephalus'' is distinguished by the thickness and upward curve of its temporal arch behind the eyes. It also has a sharply sloped snout, large eye sockets, and tusks that are positioned forward in the upper jaw. The intertemporal region at the top of the skull between the two

temporal fenestra An infratemporal fenestra, also called the lateral temporal fenestra or simply temporal fenestra, is an opening in the skull behind the orbit in some animals. It is ventrally bordered by a zygomatic arch. An opening in front of the eye sockets, ...

e is very wide.

History

The type species ''S. alticeps'' was first named by paleontologists

Robert Broom Robert Broom FRS FRSE (30 November 1866 6 April 1951) was a British- South African doctor and palaeontologist. He qualified as a medical practitioner in 1895 and received his DSc in 1905 from the University of Glasgow. From 1903 to 1910, he ...

and

Sidney H. Haughton Sidney Henry Haughton FRS (7 May 1888 – 24 May 1982) was an English-born South African paleontologist and geologist best known for his description of the sauropodomorph dinosaur '' Melanorosaurus'' in 1924, and his work on the geology of ...

in 1913. Broom and Haughton regarded it as a species of ''Dicynodon'', calling it ''D. alticeps''. In 1934, paleontologist E. C. N. van Hoepen considered ''D. alticeps'' to be distinct from other ''Dicynodon'', and placed it in its own genus ''Sintocephalus''. Van Hoepen also reassigned ''Dicynodon gilli'', ''Dicynodon jouberti'', and ''Dicynodon woodwardi'' to this genus. ''S. gilli'' and ''S. woodwardi'' were later considered valid species of ''Dicynodon'' (although they are currently classified in the genera ''

Dinanomodon ''Dinanomodon'' is a genus of dicynodont from Late Permian (Changhsingian) of the ''Lystrosaurus'' Assemblage Zone, Katberg Formation, and ''Cistecephalus'' Assemblage Zone, Balfour Formation Beaufort Group, Karoo Basin of South Africa ...

'' and '' Basilodon''), and ''S. jouberti'' has since been transferred to the genus ''

Diictodon ''Diictodon'' is an extinct genus of pylaecephalid dicynodont. These mammal-like synapsids lived during the Late Permian period, approximately 255 million years ago. Fossils have been found in the ''Cistecephalus'' Assemblage Zone of the Mad ...

''. In 1986, paleontologist A. S. Brink synonymized the type species ''S. alticeps'' with ''Dicynodon lacerticeps''. Because a genus is defined by its type species, the abandonment of ''S. alticeps'' implied that the name ''Sintocephalus'' was no longer valid. However, Brink kept the name ''Sintocephalus'' for ''S. gilli''. Most other paleontologists have abandoned the use of ''Sintocephalus'' altogether. Following a phylogenetic analysis of dicynodonts by Christian F. Kammerer, Kenneth D. Angielczyk, and Jörg Fröbisch in 2011, ''Sintocephalus'' was reinstated as a valid genus including the species ''S. alticeps''. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

specimen of ''S. alticeps'' was distinguished from ''D. lacerticeps'' material, and the species was found to be separate from the ''Dicynodon''

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, ...

(which included only ''D. lacerticeps'' and ''D. huenei''). ''S. alticeps'' was placed in the family

Lystrosauridae Lystrosauridae is a family of dicynodont therapsids from the Permian and Triassic time periods. It includes two genera, ''Lystrosaurus'' and '' Kwazulusaurus''. ''Kwazulusaurus'' includes a single species, ''K. shakai'', from the Late Permian of ...

, with its closest relative being ''Basilodon woodwardi''. 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 ...

showing the

phylogenetic 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 ...

placement of ''Sintocephalus'' in the analysis of Kammerer ''et al.'' (2011):

References

{{Taxonbar, from=Q16992581 Lopingian synapsids of Africa Dicynodonts Lopingian genus first appearances Lopingian genus extinctions Anomodont genera