''Silpholestes'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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

therapsids 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 ...

. The type species ''Silpholestes jackae'' was named by South African paleontologist

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 ...

in 1948 from the ''Cistecephalus'' Assemblage Zone.

Classification

''Silpholestes'' lends its name to Silpholestidae, a family that traditionally encompassed many small therocephalians. Silpholestidae was first named by paleontologists D. M. S. Watson and

Alfred Romer Alfred Sherwood Romer (December 28, 1894 – November 5, 1973) was an American paleontologist and biologist and a specialist in vertebrate evolution. Biography Alfred Romer was born in White Plains, New York, the son of Harry Houston Romer an ...

in 1956. In addition to ''Silpholestes'', the genera '' Ictidodraco'', '' Scaloporhinus'', ''

Silphictidoides ''Silphictidoides'' is an extinct genus of therocephalian therapsids from the Late Permian of Tanzania. The type species ''Silphictidoides ruhuhuensis'' was named by German paleontologist Friedrich von Huene in 1950 from the ''Tropidostoma'' ...

'', and ''

Tetracynodon ''Tetracynodon'' is an extinct genus of therocephalian. Fossils of ''Tetracynodon'' have been found in the Karoo Basin of South Africa. Two species are known: the type species ''T. tenuis'' from the Late Permian and the species ''T. darti'' from ...

'' were all classified in Silpholestidae. Therocephalians that were once classified in this family are all very small, and have elongated and pointed snouts. Silpholestids were characterized by their short temporal openings at the back of the skull; in most therocephalians, these openings are very large and occupy much of the skull. Silpholestids were also distinguished by their wide parietal region between the temporal openings, which did not form a

sagittal crest A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are excepti ...

as in other therocephalians. Silpholestids were also characterized by their prominent

angular bone The angular is a large bone in the lower jaw (mandible) of amphibians and reptiles (birds included), which is connected to all other lower jaw bones: the dentary (which is the entire lower jaw in mammals), the splenial, the suprangular, and the ...

s at the back of the jaw, which are very deep and covered in radiating ridges. Another traditional group of small therocephalians, the scaloposaurids, have a small angular bone that does not stand out from the curvature of the jaw. Therocephalians that were grouped in Silpholestidae all have thin

zygomatic arch In anatomy, the zygomatic arch (colloquially known as the cheek bone), is a part of the skull formed by the zygomatic process of temporal bone, zygomatic process of the temporal bone (a bone extending forward from the side of the skull, over the ...

es and complete postorbital bars that enclose the back margin of the eye sockets. Most have six

incisors Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

, a pair of larger canines, and about ten postcanine teeth. Silpholestids and scaloposaurids comprised the larger group Scaloposauria, which included nearly all small-bodied therocephalians. Most scaloposaurians are now thought to represent juvenile forms of larger therocephalians, and both Silpholestidae and Scaloposauridae are no longer regarded as valid groupings. Most scaloposaurians, including ''Silpholestes'', are now regarded as basal members of the

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 ...

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. ...

. Since there has never been a comprehensive

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 ...

analysis including all scaloposaurian taxa, it is unclear whether the therocephalians once classified as silpholestidae form their own clade.

References

Lopingian synapsids of Africa Therocephalia genera Baurioidea Lopingian genus first appearances Lopingian genus extinctions {{paleo-therapsid-stub