''Rubidgea'' is a

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 ...

gorgonopsid Gorgonopsia (from the Greek Gorgon, a mythological beast, and 'aspect') is an extinct clade of sabre-toothed therapsids from the Middle to Upper Permian roughly 265 to 252 million years ago. They are characterised by a long and narrow skull ...

from the upper

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...

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 ...

and

Tanzania Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands and ...

, containing the species ''Rubidgea atrox''. The generic name ''Rubidgea'' is sometimes believed to be derived from the surname of renowned

Karoo The Karoo ( ; from the Afrikaans borrowing of the South Khoekhoe !Orakobab or Khoemana word ''ǃ’Aukarob'' "Hardveld") is a semi-desert natural region of South Africa. No exact definition of what constitutes the Karoo is available, so its ext ...

paleontologist, Professor Bruce Rubidge, who has contributed to much of the research conducted on

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 of the

Karoo Basin The Karoo Supergroup is the most widespread stratigraphy, stratigraphic unit in Africa south of the Kalahari Desert. The group (stratigraphy), supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Pennsylvan ...

. However, this generic name was actually erected in honor of Rubidge's paternal grandfather, Sydney Rubidge, who was a renowned fossil hunter. Its species name ''atrox'' is derived from Latin, meaning “fierce, savage, terrible”. ''Rubidgea'' is part of the

gorgonopsia Gorgonopsia (from the Greek Gorgon, a mythological beast, and 'aspect') is an extinct clade of sabre-toothed therapsids from the Middle to Upper Permian roughly 265 to 252 million years ago. They are characterised by a long and narrow skull, a ...

n subfamily

Rubidgeinae Rubidgeinae is an extinct subfamily of gorgonopsid therapsids known only from Africa. They were among the largest gorgonopsians, and their fossils are common in the Cistecephalus and Daptocephalus assemblage zones of the Karoo Basin. They lived ...

, 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 ...

group of large-bodied gorgonopsians restricted to the Late

(

Lopingian The Lopingian is the uppermost series/last epoch of the Permian. It is the last epoch of the Paleozoic. The Lopingian was preceded by the Guadalupian and followed by the Early Triassic. The Lopingian is often synonymous with the informal terms l ...

). The subfamily

first appeared in the ''Tropidostoma'' Assemblage Zone. They reached their highest diversity in the ''

Cistecephalus ''Cistecephalus'' is an extinct genus of dicynodont therapsid from the Late Permian of southern Africa (South Africa and Zambia). It was a small, specialised, burrowing dicynodont, possibly with habits similar to a modern mole. The head was flat ...

'' and ''

Daptocephalus ''Daptocephalus'' is an extinct genus of non- mammalian synapsid anomodont dicynodont, it which was found in Late Permian strata, in a biozone known precisely for the presence of fossils of this dicynodont, the ''Daptocephalus'' Zone, in the Ka ...

'' assemblage zones 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 ...

History of discovery

The first ''Rubidgea''

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

was discovered by C. J. M. "Croonie" Kitching, the father of renowned paleontologist

James Kitching James William Kitching (6 February 1922 – 24 December 2003) was a South African vertebrate palaeontologist and regarded as one of the world’s greatest fossil finders. Career His work in the southern hemisphere, including Antarctica, led ...

, on the farm Doornberg outside the small town

Nieu-Bethesda Nieu-Bethesda (Afrikaans for ''New Bethesda'') is a village in the Eastern Cape at the foot of the Sneeuberge, approximately north of Graaff Reinet. It was founded in 1875 as a church town, like many other Karoo villages, and attained municipa ...

sometime in the 1930s. In a paper published in 1938,

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 ...

named the fossil ''Rubidgea kitchingi''. Broom noted the large size of the new

, stating that it was a new

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

. Subsequent discoveries in the following decades confirmed Broom's suspicions that a new subfamily of

ns should be categorised, and the

was erected.

Description

''Rubidgea'' was the largest African

ns and one of the largest gorgonopsians known to have lived. The largest specimens had skulls that measure up to in length. ''Rubidgea'' was a heavily-built, large-bodied

apex predator An apex predator, also known as a top predator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the highest trophic lev ...

, and sported a thick skull with long, sabre-like

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 ...

. The

group as a whole were the largest gorgonopsians known to have lived, and are characterised by their robust skeletal features, particularly their skulls which are heavily- pachyostosed. The genus ''Rubidgea'' is composed of three species, ''R. atrox'', ''R. platyrhina'', and ''R. majora''.

Classification

The

are a subfamily of

gorgonopsids that have only been found in

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

. They are composed of six

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

and 17

. The

are closely related to their sister group, the

Inostranceviinae Inostranceviinae is an extinct subfamily of gorgonopsid therapsids that lived during the Late Permian. Only two genera are known, both from Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning East ...

, which have only been found in

Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...

. Out 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, ...

, the

systematics Biological systematics is the study of the diversification of living forms, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees (synonyms: cladograms, phylogenetic tre ...

of the

is the best resolved due to their distinctive character traits. The

of other

n subfamilies remain chaotic due to a high degree of

cranial Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

homomorphism between

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

, making it difficult to distinguish different taxa effectively. The cladogram below (Kammerer and Rubidge 2022) displays the currently accepted systematic relationships of the

Gorgonopsia Gorgonopsia (from the Greek Gorgon, a mythological beast, and 'aspect') is an extinct clade of sabre-toothed therapsids from the Middle to Upper Permian roughly 265 to 252 million years ago. They are characterised by a long and narrow skull, a ...

Correlation

Numerous

, including rubidgenae gorgonopsids, are used as biostratigraphic markers in other African Basins, such as the Upper Madumabisa Mudstone Formation of

Zambia Zambia (), officially the Republic of Zambia, is a landlocked country at the crossroads of Central Africa, Central, Southern Africa, Southern and East Africa, although it is typically referred to as being in Southern Africa at its most cent ...

, and the Chiweta Beds of

Malawi Malawi (; or aláwi Tumbuka: ''Malaŵi''), officially the Republic of Malawi, is a landlocked country in Southeastern Africa that was formerly known as Nyasaland. It is bordered by Zambia to the west, Tanzania to the north and northeast ...

. ''Rubidgea'' fossils have been recovered from the

Usili Formation The Usili Formation is a Late Permian geologic formation in Tanzania. It preserves fossils of many terrestrial vertebrates from the Permian, including temnospondyls, pareiasaurs, therapsids and the archosauromorph ''Aenigmastropheus''. History ...

, indicating

biostratigraphic Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictionary of Bio ...

correlation with upper

-aged deposits in

.Parrington, F. R. "A new genus of gorgonopsid from East Africa." Annals of the South African Museum 64 (1974): 47-52. No

rubidgeinae Rubidgeinae is an extinct subfamily of gorgonopsid therapsids known only from Africa. They were among the largest gorgonopsians, and their fossils are common in the Cistecephalus and Daptocephalus assemblage zones of the Karoo Basin. They lived ...

fossils have been found outside of African deposits to date, although the

are considered to be their Russian counterparts.

References

{{Taxonbar, from=Q1977910 Gorgonopsia Prehistoric therapsid genera Permian synapsids of Africa Fossil taxa described in 1938