Phorcys dubei

Phorcys; Temporal range: Middle Permian, Wordian–Capitanian PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Synapsida
Clade:	Therapsida
Clade:	† Gorgonopsia
Genus:	† Phorcys ; Kammerer & Rubidge, 2022
Species:	†P. dubei
Binomial name
	†Phorcys dubei; Kammerer & Rubidge, 2022

Last updated May 24, 2023

Phorcys is an extinct genus of gorgonopsian (predatory therapsids, related to modern mammals) that lived during the Middle Permian period (Guadalupian) of what is now South Africa. It is known from two specimens, both portions from the back of the skull, that were described and named in 2022 as a new genus and species P. dubei by Christian Kammerer and Bruce Rubidge. The generic name is from Phorcys of Greek mythology, the father of the Gorgons from which the gorgonopsians are named after, and refers to its status as one of the oldest representatives of the group in the fossil record. Phorcys was recovered from the lowest strata of the Tapinocephalus Assemblage Zone (AZ) of the Beaufort Group, making it one of the oldest known gorgonopsians in the fossil record—second only to fragmentary remains of an indeterminate gorgonopsian from the older underlying Eodicynodon Assemblage Zone.

Phorcys was also unexpectedly large for an early gorgonopsian with a total skull length estimated at ~30 cm (12 in), comparable to in size to later gorgonopsians and notably larger than the similarly aged Eriphostoma with skull lengths of only ~10–15 cm (3.9–5.9 in). This contradicts prior suggestions that gorgonopsians only achieved larger sizes, and associated top predator status, following the extinction of dinocephalians and large therocephalian therapsids in the Late Permian. Indeed, Phorcys was comparable in size to a contemporary specimen of a scylacosaurid therocephalian with a skull estimated to be ~21 centimetres (8.3 in) long, and even to the slightly older anteosaur Australosyodon (skull length ~26 cm (10 in)). Phorcys and other gorgonopsians may then have been top predators in some Middle Permian assemblages.

Discovery and naming

Only two specimens of Phorcys are known, each consisting of weathered partial skulls broken off before the snout. Both specimens were collected from a locality near Delportsrivier, a farm in Jansenville of Eastern Cape Province, South Africa, and are catalogued as BP/1/5850 and BP/1/5851 by the Evolutionary Studies Institute of the University of the Witwatersrand, where they are stored. These specimens were initially reported on in 1995 by palaeontologist Bruce S. Rubidge,^[1] however they would not be described and named as a new genus and species, Phorcys dubei, until 2022 by Rubidge and fellow palaeontologist Christian F. Kammerer.^[2] The two specimens were prepared by Mr. Charlton Dube (who himself collected BP/1/5850), and the specific name dubei honours his contribution and commends his skills at fossil preparation. The generic name Phorcys is after Phorcys of ancient Greek mythology, a primordial god and the father of the Gorgons. The name alludes to its status as one of the earliest known gorgonopsians, the group itself being named after the mythological Gorgons with many genera including "gorgon" in their own names.^[2]

Although both specimens are weathered and damaged, BP/1/5851 is considerably more complete and so was designated the holotype specimen by Kammerer and Rubidge. It preserves most of the skull from the occiput (the back face of the skull) up to the orbits, including the basicranium (the floor of the skull beneath the braincase), an eroded upper surface preserving the intact preparietal and portions of the surrounding frontals and parietal bones, with a broken left zygomatic arch and a left palatine displaced into the left orbit, the only known bone from the front half of the skull. The paratype is less complete and more badly weathered, consisting mostly of a partial occiput with associated parts of the skull roof and the basicranium (as well as other unidentified bone fragments).^[2]

The locality where both specimens were recovered belongs to the eastern exposures of the Abrahamskraal Formation (of which historically were labelled the Koonap Formation), the lowest (and so oldest) geological formation in the fossiliferous Permo-Triassic aged Beaufort Group of the Karoo Basin. The layers of the Abrahamskraal Formation near Jansenville are typically correlated to the lower Tapinocephalus Assemblage Zone (AZ) fauna.^[3] However, due to the unique faunal assemblage known from these localities that are seemingly absent from the rest of the Tapinocephalus AZ (including Phorcys), it has been suggested they may represent a distinct faunal assemblage between the younger Tapinocephalus AZ and the older underlying Eodicynodon Assemblage Zone.^[4] This biostratigraphic position corresponds to a Middle Permian (or Guadalupian) age, dating to somewhere within the Wordian to Capitanian stages. Phorcys then represents one of the oldest known gorgonopsians worldwide, and certainly the oldest named species. Only one other specimen is older, having been discovered in the underlying Eodicynodon AZ. This specimen, NMQR 2982, was also described by Kammerer and Rubidge in the same article as Phorcys. However, the specimen only consists of a pair of jaw tips and lacks any characteristics diagnosable to the genus or species level, and so Kammerer and Rubidge referred NMQR 2982 to Gorgonopsia indet (although they acknowledged the possibility it may be conspecific with Phorcys, lack of overlapping material makes this impossible to determine).^[2]

Description

Little can be said for the overall anatomy of Phorcys as it is only known from partial skulls missing everything in front of the eyes. Nonetheless, it is estimated to be a relatively large-bodied gorgonopsian with a complete skull length estimated at 30 cm (12 in), assuming it had similar proportions to the related Gorgonops . For comparison, the largest Late Permian gorgonopsians such as Inostrancevia and Rubidgea reached skull lengths in excess of 40 cm (16 in).^[5] Collectively, the preserved portions of Phorcys make up the rear of the skull behind the eyes, including the postorbital bar, zygomatic arch, the occiput, and much of the basicranium. Only one bone from the front of the skull is known, the palatine, which bears numerous palatal teeth. Although incomplete and eroded, Phorcys preserves various characteristics that mark it as a gorgonopsian from other groups of therapsids.

One such feature is the width of the postorbital bar behind the eyes, which increases in its front-to-back width from the roof of the skull down to where it meets the jugal on the zygomatic arch, more than doubling its width from 2.2 cm to 4.5 cm. Such an extreme expansion is unique to gorgonopsians, as is its convex border of the temporal fenestra, which in other predatory therapsids is often concave to undercut the orbit. Although the roof of the skull has been narrowed by erosion, the area between the two temporal fenestra (the intratemporal region) is inferred to have been broad and flat like other gorgonopsians from a broken edge still attached to the back of the postorbital, revealing its true extent. Phorcys also had a large preparietal (a bone unique to just a few therapsid groups, including gorgonopsians) with a rounded front edge in the characteristic shape for gorgonopsians. The occiput is broad and low, wider than it is tall as typical of gorgonopsians, and has a vertical face. This contrasts with the only other gorgonopsian from the Tapinocephalus Assemblage Zone, Eriphostoma , which consistently preserves an occiput that slopes up and forwards. Like other gorgonopsians, the occiput has a sulcus (or furrow) in the squamosal bone on either side, mostly exposed on the back but curving around partially onto the side of the zygomatic arch. The occiput also sports a prominent nuchal crest running vertically down the centre and widening from the skull roof down to the circular foramen magnum (the opening for the spinal cord, bordered by the occipital condyle beneath). This crest is common in gorgonopsians and served for muscle attachment, but it is especially robust in Phorcys for its body size.^[2]

The basioccipital, a bone in the basicranium that forms the bottom rim of the foramen magnum and extends below to form the floor of the back of the braincase, distinguishes Phorcys from all other known gorgonopsians. It sports a pair of knob-like protuberances at the back and inner margins of the "basal tubera", ovoid projections of bone that run from the basiccopital and inwards on to the fused parabasisphenoid in front. These protuberances are unknown in any other gorgonopsian, and are present in both specimens. The parabasisphenoid itself is typical of gorgonopsians, sporting the characteristic tall, thin, vertical blade of bone on the narrow cultriform process that extends forwards down the middle of the palate. The epipterygoid, an elongated strap-like process of bone, rise up from either side of the basicranium to where they would contact the parietal bones above, as is the typical form for therapsids.^[2]

The only bone from the front half of the skull known is the palatine from the roof of the mouth. Like other gorgonopsians, the palatine sports a prominent bony boss with palatal teeth. In Phorcys, the palatal teeth are arranged in a delta-shaped row on the boss, resembling a forward-pointing arrowhead or inverted 'V', consisting of 10 teeth. This delta-shaped tooth row is uncommon among gorgonopsians, but is found in other early genera such Gorgonops and Eriphostoma.^[6] The 10th palatal tooth (at the rear of the lateral margin) is conspicuously larger than the rest of the palatal teeth (0.5 cm vs 0.2-0.3 cm), although this was interpreted as an individually unique variation in tooth replacement, as the palatal teeth of gorgonopsians are not known to show consistent size variation within species.^[2]

Classification

Although known from little material, what is preserved is enough to demonstrate that Phorcys was undoubtedly a gorgonopsian. Phorcys can be diagnosed and distinguished from all other gorgonopsians by the knob-like protuberances between the basal tubera and the occipital condyle on the underside of the skull. It is also distinguished from the only other known Tapinocephalus Assemblage Zone gorgonopsian Eriphostoma by its larger size, vertical occiput and proportionately deeper zygomatic arch.^[2]

To determine its relationship to other gorgonopsians, Kammerer and Rubidge performed a phylogenetic analysis using a complete dataset of all currently valid gorgonopsian genera. Similar to previous analyses, they recovered Nochnitsa and Viatkogorgon as the earliest-diverging (basal) gorgonopsians, with the remaining genera split into two clades, one containing Russian gorgonopsians and the other African.^[7]Phorcys was found in a polytomy at the base of the African clade with Eriphostoma, Gorgonops and the remaining African gorgonopsians. This basal position among African gorgonopsians is consistent with its age, however, at the same time it draws out the existing ghost lineages (inferred ancestral lineages with missing fossil records) of the earlier-diverging Laurasian gorgonopsians back to the Wordian of the middle Permian at minimum. However, Kammerer and Rubidge considered this result preliminary due to the fragmentary nature of the known material, and noted that this position in the tree was weakly supported with only one coded characteristic (the straight orientation of the subtemporal zygoma) uniting it with other African gorgonopsians in this analysis (a trait that is itself variable in this clade). Nonetheless, an additional trait that wasn't coded for in their analysis may strengthen a relationship to the African gorgonopsians, the shape of the parabasisphenoid blade of the braincase. In Phorcys, this bone has only slight variation along its bottom margin, unlike the notable semi-circular blades of the Russian gorgonopsians but very comparable to those in the African clade.^[2]

The cladogram below depicting the relationship of Phorcys in Gorgonopsia follows the results of Kammerer and Rubidge (2022):^[2]

Life restoration of Eriphostoma (speculatively restored with whiskers), a possible close relative of Phorcys Eoarctops.jpg — Life restoration of *Eriphostoma* (speculatively restored with whiskers), a possible close relative of *Phorcys*

"Russian clade"

	Pravoslavlevia

	Inostrancevia

"African clade"

Phorcys

	Smilesaurus

	Arctops

	Arctognathus

	Rubidgeinae

Palaeoecology

In what would become the eastern Abrahamskraal Formation, Phorcys coexisted with an unusual assortment of therapsids and may have been part of a potentially distinct faunal assemblage from the rest of the Tapinocephalus Assemblage Zone. Two other therapsid genera are known only from these units, the predatory burnietamorph Pachydectes and the herbivorous early dicynodont Lanthanostegus , an unusual genus with markedly forward-facing eye sockets.^[2]^[4] A scylacosaurid therocephalian is also known from the same horizon, estimated to have a skull roughly ~21 cm (8.3 in) long and comparable in size to, if not smaller than Phorcys. It is possible then that Phorcys was the top predator in this assemblage, in contrast to therapsid faunas in the upper Tapinocephalus AZ where therocephalians and the even larger anteosaurs dominated.^[2]

Gorgonopsian ecological evolution

The presence of a relatively large-bodied early gorgonopsian like Phorcys so low in the Tapinocephalus AZ complicates previously proposed narratives for the ecological evolution of predatory therapsids. Prior to its discovery, gorgonopsians from older therapsid faunas were small—such as Viatkogorgon and Nochnitsa from Russia and the African Eriphostoma—and were in low abundance, while the largest and most diverse predators were either large therocephalians (namely scylacosaurids and lycosuchids) or giant anteosaurs. This lead palaeontologists Christian Kammerer and Vladimir Masyutin to suggest in 2018 that gorgonopsians and therocephalians were niche partitioning by body size, with gorgonopsians occupying smaller predatory roles than larger therocephalians. Indeed, gorgonopsians only appeared to achieve larger sizes until after the extinction of the large therocephalians at the end-Guadalupian extinction event, which they suggested was an ecological release for gorgonopsians.^[7]

Phorcys (as well as the similarly sized indeterminate gorgonopsian from the Eodicynodon AZ), however, demonstrate that early gorgonopsians did achieve large sizes comparable to later species and contemporary therocephalians, such as the scylacosaurid mentioned above. Indeed, while anteosaurs were the top predators in the upper Tapinocephalus AZ and were substantially larger than other predatory therapsids, the older Australosyodon from the underlying Eodicynodon AZ was relatively small and comparably sized to both Phorcys and scylacosaurids with a skull 26 cm (10 in) long. With Phorcys reaching comparable or potentially even greater sizes than either early anteosaurs and therocephalians, Kammerer and Rubidge contemplated the possibility that gorgonopsians like Phorcys may have been top predators in these early Middle Permian assemblages.^[2]

It remains unclear why similarly large gorgonopsians appear to be absent from later Middle Permian faunas such as in the upper Tapinocephalus AZ. Gorgonopsian fossils are relatively under-sampled from these ages, so it is possible that they were rare parts of their ecosystems—although this would not explain why similar sized therocephalians were much more abundant. Alternatively, large therocephalians and gorgonopsians may have indeed been partitioned by size, but only following the extinction of large gorgonopsians like Phorcys in the Capitanian.^[2]

Related Research Articles

Dinocephalians are a clade of large-bodied early therapsids that flourished in the Early and Middle Permian between 279.5 and 260 million years ago (Ma), but became extinct during the Capitanian mass extinction event. Dinocephalians included herbivorous, carnivorous, and omnivorous forms. Many species had thickened skulls with many knobs and bony projections. Dinocephalians were the first non-mammalian therapsids to be scientifically described and their fossils are known from Russia, China, Brazil, South Africa, Zimbabwe, and Tanzania.

Gorgonopsia 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, as well as elongated upper and sometimes lower canine teeth and incisors which were likely used as slashing and stabbing weapons. Postcanine teeth are generally reduced or absent. For hunting large prey, they possibly used a bite-and-retreat tactic, ambushing and taking a debilitating bite out of the target, and following it at a safe distance before its injuries exhausted it, whereupon the gorgonopsian would grapple the animal and deliver a killing bite. They would have had an exorbitant gape, possibly in excess of 90°, without having to unhinge the jaw.

<i>Gorgonops</i> Extinct genus of therapsids

Gorgonops is an extinct genus of gorgonopsian therapsid, of which it is the type genus. Gorgonops lived during the Late Permian (Wuchiapingian), about 260–254 million years ago in what is now South Africa.

Biarmosuchia is an extinct clade of non-mammalian synapsids from the Permian. Biarmosuchians are the most basal group of the therapsids. They were moderately-sized, lightly built carnivores, intermediate in form between basal sphenacodont "pelycosaurs" and more advanced therapsids. Biarmosuchians were rare components of Permian ecosystems, and the majority of species belong to the clade Burnetiamorpha, which are characterized by elaborate cranial ornamentation.

Inostrancevia is an extinct genus of large carnivorous therapsids who lived during the Late Permian in what is now European Russia and South Africa. The first known fossils of this gorgonopsian were discovered in the Northern Dvina, where two almost complete skeletons was exhumed. Subsequently, several other fossil material was discovered in various oblasts, and these finds will lead to a confusion about the exact number of valid species in the country, before only three of them where officially recognized : I. alexandri, I. latifrons and I. uralensis. More recent research carried out in South Africa has discovered fairly well-preserved remains of the genus, being attributed to the species I. africana. The whole genus is named in honor of Alexander Inostrantsev, professor of Vladimir P. Amalitsky, the paleontologist who described the taxon.

<i>Dinogorgon</i> Extinct genus of therapsids

Dinogorgon is a genus of gorgonopsid from the Late Permian of South Africa and Tanzania. The generic name Dinogorgon is derived from Greek, meaning "terrible gorgon", while its species name rubidgei is taken from the surname of renowned Karoo paleontologist, Professor Bruce Rubidge, who has contributed to much of the research conducted on therapsids of the Karoo Basin. The type species of the genus is D. rubidgei.

Anteosaurus is an extinct genus of large carnivorous dinocephalian synapsid. It lived at the end of the Guadalupian during the Capitanian stage, about 265 to 260 million years ago in what is now South Africa. It is mainly known by cranial remains and few postcranial bones. With its skull reaching 80–90 cm (31–35 in) in length and a body size estimated at more than 5 m (16 ft) in length, and 500 to 600 kg in weight, Anteosaurus was the largest known carnivorous non-mammalian synapsid and the largest terrestrial predator of the Permian period. Occupying the top of the food chain in the Middle Permian, its skull, jaws and teeth show adaptations to capture large prey like the giants titanosuchids and tapinocephalids dinocephalians and large pareiasaurs.

The Tapinocephalus Assemblage Zone is a tetrapod assemblage zone or biozone which correlates to the middle Abrahamskraal Formation, Adelaide Subgroup of the Beaufort Group, a fossiliferous and geologically important geological Group of the Karoo Supergroup in South Africa. The thickest outcrops, reaching approximately 2,000 metres (6,600 ft), occur from Merweville and Leeu-Gamka in its southernmost exposures, from Sutherland through to Beaufort West where outcrops start to only be found in the south-east, north of Oudshoorn and Willowmore, reaching up to areas south of Graaff-Reinet. Its northernmost exposures occur around the towns Fraserburg and Victoria West. The Tapinocephalus Assemblage Zone is the second biozone of the Beaufort Group.

<i>Rubidgea</i> Extinct genus of therapsids

Rubidgea is a genus of gorgonopsid from the upper Permian of South Africa and Tanzania, containing the species Rubidgea atrox. The generic name Rubidgea is sometimes believed to be derived from the surname of renowned Karoo paleontologist, Professor Bruce Rubidge, who has contributed to much of the research conducted on therapsids of the Karoo Basin. 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 gorgonopsian subfamily Rubidgeinae, a derived group of large-bodied gorgonopsians restricted to the Late Permian (Lopingian). The subfamily Rubidgeinae first appeared in the Tropidostoma Assemblage Zone. They reached their highest diversity in the Cistecephalus and Daptocephalus assemblage zones of the Beaufort Group in South Africa.

Lemurosaurus is a genus of extinct biarmosuchian therapsids from the Late Permian of South Africa. The generic epithet Lemursaurus is a mix of Latin, lemures “ghosts, spirits”, and Greek, sauros, “lizard”. Lemurosaurus is easily identifiable by its prominent eye crests, and large eyes. The name Lemurosaurus pricei was coined by paleontologist Robert Broom in 1949, based on a single small crushed skull, measured at approximately 86 millimeters in length, found on the Dorsfontein farm in Graaff-Reinet. To date, only two skulls of the Lemurosaurus have been discovered, so body size is unknown. The second larger, more intact, skull was found in 1974 by a team from the National Museum, Bloemfontein.

Styracocephalus platyrhynchus (Greek for “spiked-head”) is an extinct genus of dinocephalian therapsid that existed during the Mid-Permian throughout South Africa, but mainly in the Karoo Basin. It is often referred to by its single known species Styracocephalus platyrhynchus. The Dinocephalia clade consisted of the largest land vertebrates and herbivores during the early to mid-Permian. This period is often also referred to as the Guadalupian epoch, approximately 270 to 260 million years ago.

Aelurosaurus is a small, carnivorous, extinct genus of gorgonopsian therapsids from the Middle Permian to Late Permian of South Africa. It was discovered in the Karoo Basin of South Africa, and first named by Richard Owen in 1881. It was named so because it appeared to be an ancestor for cat-like marsupials, but not yet a mammal itself. It contains five species, A. felinus, A. whaitsi, A. polyodon, A. wilmanae, and A.? watermeyeri. A. felinus, the type species, is generally well described with established features, while the other four species are not due to their poorly preserved holotypes.

Scylacops is an extinct genus of Gorgonopsia. It was first named by Broom in 1913, and contains two species, S. bigendens, and S. capensis. Its fossils have been found in South Africa and Zambia. It is believed to be closely related to the Gorgonopsian Sauroctonus progressus. Scylacops was a moderately sized Gorgonopsid.

Eriphostoma is an extinct genus of gorgonopsian therapsids known from the Middle Permian of Tapinocephalus Assemblage Zone, South Africa. It has one known species, Eriphostoma microdon, and was first named by Robert Broom in 1911. It is the oldest known gorgonopsian and among the smallest and most basal members of the clade.

Scymnosaurus is an extinct genus of therocephalian therapsids, first described by Robert Broom in 1903. There are three species that still take the name Scymnosaurus, S. ferox, S. watsoni and S. major, with a fourth, S. warreni, now identified as Moschorhinus warreni. Each of these have now been reclassified into Lycosuchidae incertae sedis.

"Dixeya" nasuta is a species of the predatory gorgonopsian therapsids from the Late Permian of East Africa, known from fossils found in what is now Tanzania. The species has a complicated taxonomic history, it was originally named as a second species of the genus Dixeya which is now considered a junior synonym of Aelurognathus. "D." nasuta itself, however, was not moved to Aelurognathus, and although it was instead tentatively referred to Arctognathus at first it has since been recognised to not belong to this genus either. This situation leaves "Dixeya" nasuta without a formal genus name. It was proposed to belong to a new distinct genus, named "Njalila", that was informally proposed for the species in a PhD thesis, but this name has not yet been formally published and is currently a nomen nudum. "D." nasuta has been characterised from other gorgonopsians by a combination of its straight snout profile, upturned and 'pinched' nose, and curved jaw margin.

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 during the Late Permian, and became extinct at the end of the Permian.

Nochnitsa is a genus of gorgonopsian therapsid from the Kotelnich red beds of Permian Russia. It contains one species, Nochnitsa geminidens. It the most basal known gorgonopsian and among the smallest members of the clade known to date.

Thliptosaurus is an extinct genus of small kingoriid dicynodont from the latest Permian period of the Karoo Basin in KwaZulu-Natal, South Africa. It contains the type and only known species T. imperforatus. Thliptosaurus is from the upper Daptocephalus Assemblage Zone, making it one of the youngest Permian dicynodonts known, living just prior to the Permian mass extinction. It also represents one of the few small bodied dicynodonts to exist at this time, when most other dicynodonts had large body sizes and many small dicynodonts had gone extinct. The unexpected discovery of Thliptosaurus in a region of the Karoo outside of the historically sampled localities suggests that it may have been part of an endemic local fauna not found in these historic sites. Such under-sampled localities may contain 'hidden diversities' of Permian faunas that are unknown from traditional samples. Thliptosaurus is also unusual for dicynodonts as it lacks a pineal foramen, suggesting that it played a much less important role in thermoregulation than it did for other dicynodonts.

Vetusodon is an extinct genus of cynodonts belonging to the clade Epicynodontia. It contains one species, Vetusodon elikhulu, which is known from four specimens found in the Late Permian Daptocephalus Assemblage Zone of South Africa. With a skull length of about 18 centimetres (7.1 in), Vetusodon is the largest known cynodont from the Permian. Through convergent evolution, it possessed several unusual features reminiscent of the contemporary therocephalian Moschorhinus, including broad, robust jaws, large incisors and canines, and small, single-cusped postcanine teeth.

References

↑ Rubidge, Bruce S., ed. (1995). Biostratigraphy of the Beaufort Group (Karoo Supergroup). South African Committee for Stratigraphy. Biostratigraphic Series 1. Pretoria: Council for Geoscience. ISBN 978-1-87-506124-2. OCLC 35233710.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 Kammerer, C. F.; Rubidge, B. S. (2022). "The earliest gorgonopsians from the Karoo Basin of South Africa". Journal of African Earth Sciences. 194: 104631. Bibcode:2022JAfES.19404631K. doi:10.1016/j.jafrearsci.2022.104631. S2CID 249977414.
↑ M.O. Day; B.S. Rubidge (2020). "Biostratigraphy of the Tapinocephalus Assemblage Zone (Beaufort Group, Karoo Supergroup), South Africa". South African Journal of Geology. 123 (2): 149–164. Bibcode:2020SAJG..123..149D. doi:10.25131/sajg.123.0012. S2CID 225815517.
1 2 Rubidge, B. S.; Day, M. O.; Benoit, J. (2021). "New Specimen of the Enigmatic Dicynodont Lanthanostegus mohoii (Therapsida, Anomodontia) from the Southwestern Karoo Basin of South Africa, and its Implications for Middle Permian Biostratigraphy". Frontiers in Earth Science. 9: Article 668143. Bibcode:2021FrEaS...9..414R. doi: 10.3389/feart.2021.668143 . S2CID 235258937.
↑ Kammerer, Christian F. (2016). "Systematics of the Rubidgeinae (Therapsida: Gorgonopsia)". PeerJ. 4: e1608. doi:10.7717/peerj.1608. ISSN 2167-8359. PMC 4730894 . PMID 26823998.
↑ Kammerer, Christian F. (2014). "A Redescription of Eriphostoma microdon Broom, 1911 (Therapsida, Gorgonopsia) from the Tapinocephalus Assemblage Zone of South Africa and a Review of Middle Permian Gorgonopsians". In Kammerer, Christian F.; Angielczyk, Kenneth D.; Fröbisch, Jörg (eds.). Early Evolutionary History of the Synapsida. Vertebrate Paleobiology and Paleoanthropology. Springer. pp. 171–184. doi:10.1007/978-94-007-6841-3_11. ISBN 978-94-007-6840-6.
1 2 Kammerer, C. F.; Masyutin, V. (2018). "A new therocephalian (Gorynychus masyutinae gen. et sp. nov.) from the Permian Kotelnich locality, Kirov Region, Russia". PeerJ. 6: e4933. doi:10.7717/peerj.4933. PMC 5995100 . PMID 29900076.

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[1] Rubidge, Bruce S., ed. (1995). Biostratigraphy of the Beaufort Group (Karoo Supergroup). South African Committee for Stratigraphy. Biostratigraphic Series 1. Pretoria: Council for Geoscience. ISBN 978-1-87-506124-2. OCLC 35233710.

[desc-2] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Kammerer, C. F.; Rubidge, B. S. (2022). "The earliest gorgonopsians from the Karoo Basin of South Africa". Journal of African Earth Sciences. 194: 104631. Bibcode:2022JAfES.19404631K. doi:10.1016/j.jafrearsci.2022.104631. S2CID 249977414.

[3] M.O. Day; B.S. Rubidge (2020). "Biostratigraphy of the Tapinocephalus Assemblage Zone (Beaufort Group, Karoo Supergroup), South Africa". South African Journal of Geology. 123 (2): 149–164. Bibcode:2020SAJG..123..149D. doi:10.25131/sajg.123.0012. S2CID 225815517.

[lanth-4] 1 2 Rubidge, B. S.; Day, M. O.; Benoit, J. (2021). "New Specimen of the Enigmatic Dicynodont Lanthanostegus mohoii (Therapsida, Anomodontia) from the Southwestern Karoo Basin of South Africa, and its Implications for Middle Permian Biostratigraphy". Frontiers in Earth Science. 9: Article 668143. Bibcode:2021FrEaS...9..414R. doi: 10.3389/feart.2021.668143 . S2CID 235258937.

[5] Kammerer, Christian F. (2016). "Systematics of the Rubidgeinae (Therapsida: Gorgonopsia)". PeerJ. 4: e1608. doi:10.7717/peerj.1608. ISSN 2167-8359. PMC 4730894 . PMID 26823998.

[Eri2014-6] Kammerer, Christian F. (2014). "A Redescription of Eriphostoma microdon Broom, 1911 (Therapsida, Gorgonopsia) from the Tapinocephalus Assemblage Zone of South Africa and a Review of Middle Permian Gorgonopsians". In Kammerer, Christian F.; Angielczyk, Kenneth D.; Fröbisch, Jörg (eds.). Early Evolutionary History of the Synapsida. Vertebrate Paleobiology and Paleoanthropology. Springer. pp. 171–184. doi:10.1007/978-94-007-6841-3_11. ISBN 978-94-007-6840-6.

[gory-7] 1 2 Kammerer, C. F.; Masyutin, V. (2018). "A new therocephalian (Gorynychus masyutinae gen. et sp. nov.) from the Permian Kotelnich locality, Kirov Region, Russia". PeerJ. 6: e4933. doi:10.7717/peerj.4933. PMC 5995100 . PMID 29900076.

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