''Sintocephalus'' is an extinct genus of

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 ...

therapsid from the

Late Permian Late or LATE may refer to: Everyday usage * Tardy, or late, not being on time * Late (or the late) may refer to a person who is dead Music * ''Late'' (The 77s album), 2000 * Late (Alvin Batiste album), 1993 * Late!, a pseudonym used by Dave Groh ...

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 ...

. 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 under ...

. The

type species In International_Code_of_Zoological_Nomenclature, 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 spe ...

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

Dicynodon ''Dicynodon'' (from Ancient Greek '' δίς'' "two" and '' κυνόδους'' "canine teeth", often translated to "two canine-teeth" or "two dog-teeth") is a genus of dicynodont therapsid that lived in southern and eastern Africa during the Lat ...

''. 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 Temporal fenestrae are openings in the temporal region of the skull of some amniotes, behind the orbit (eye socket). These openings have historically been used to track the evolution and affinities of reptiles. Temporal fenestrae are commonly (al ...

e is very wide.

History

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

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

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

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 ...

''. 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 (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

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

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 ...

(which included only ''D. lacerticeps'' and ''D. huenei''). ''S. alticeps'' was placed in the family Lystrosauridae, with its closest relative being ''Basilodon woodwardi''. 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 ...

showing the

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

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

References

{{Taxonbar, from=Q16992581 Lopingian synapsids of Africa Bidentalia Lopingian genus first appearances Lopingian genus extinctions