''Silpholestes'' 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 ...

therocephalian 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

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 ...

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

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 ...

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 Prof David Meredith Seares Watson FRS FGS HFRSE LLD (18 June 1886 – 23 July 1973) was the Jodrell Professor of Zoology and Comparative Anatomy at University College, London from 1921 to 1951. Biography Early life Watson was born in the Highe ...

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 ''Ictidodraco'' is an extinct genus of therocephalian therapsids from the Late Permian of South Africa. The type species ''Ictidodraco longiceps'' was named by South African paleontologists Robert Broom and John T. Robinson in 1948 from the ''Ci ...

'', '' 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'' Ass ...

'', 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'' fro ...

'' 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 exceptiona ...

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 art ...

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, or cheek bone, is a part of the skull formed by the zygomatic process of the temporal bone (a bone extending forward from the side of the skull, over the opening of the ear) and the temporal process of the zygomati ...

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, wh ...

, a pair of larger

canines Canine may refer to: Zoology and anatomy * a dog-like Canid animal in the subfamily Caninae ** ''Canis'', a genus including dogs, wolves, coyotes, and jackals ** Dog, the domestic dog * Canine tooth, in mammalian oral anatomy People with the surn ...

, 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 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, ...

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 (; 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 ...

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 Baurioids Lopingian genus first appearances Lopingian genus extinctions {{paleo-therapsid-stub