Akidnognathidae

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Akidnognathidae
Temporal range: Late Permian - Early Triassic 254–247  Ma
Jiufengia.png
Holotype skull of Jiufengia jiai
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade:† Therocephalia
Clade:† Eutherocephalia
Family:† Akidnognathidae
Nopcsa, 1928
Genera
List
Synonyms
  • Euchambersiidae Boonstra, 1934
  • Annatherapsididae Kuhn, 1963
  • Moschorhinidae Mendrez, 1974

Akidnognathidae is an extinct family of therocephalian therapsids from the Late Permian and Early Triassic of South Africa, Russia and China. The family includes many large-bodied therocephalians that were probably carnivorous, including Moschorhinus and Olivierosuchus . One akidnognathid, Euchambersia , may even have been venomous. Akidnognathids have robust skulls with a pair of large caniniform teeth in their upper jaws. The family is morphologically intermediate between the more basal therocephalian group Scylacosauridae and the more derived group Baurioidea.

Contents

Research history

The first known fossils of akidnognathids consists of two skulls which were discovered during a series of excavations carried out from 1899 until 1914 by Vladimir Amalitsky and his companion Anna P. Amalitsky  [ ru ] in the Northern Dvina, in present-day European Russia. In an article published posthumously in 1922, Amalitsky established a new taxon of therocephalians under the name Anna petri, in honor of his companion. In his description he judges it to be similar to Scylacosaurus . [1] In 1963, Oskar Kuhn proposed changing the name of the genus to Annatherapsidus , seeing that Anna was an already preoccupied taxon. Currently, Annatherapsidus is the only akidnognathid known from Russian territory. [2]

The first akidnognathid to be described was the type genus Akidnognathus , named in 1918 by Sidney Henry Haughton from a skull discovered by reverend John H. Whaits in the Beaufort Group, South Africa. The specimen comes more precisely from the upper Cistecephalus Assemblage Zone, within the Karoo Supergroup. [3] It is in the Karoo supergroup where the majority of known akidnognathids will be identified, [2] with at least two additional genera, namely Euchambersia and Proalopecopsis , also from the upper Cistecephalus Assemblage Zone. [4]

Akidnognathids were historically only reported from Russia and South Africa, but it was from 2017 that paleontologists Jun Liu and Fernando Abdala described several taxa from the Naobaogou Formation, in Inner Mongolia, China, from several fossils collected on this fossil site since 2009. [2] [5] [6] Among these described taxa, the two authors identify a second species of Euchambersia, a genus that was previously reported only in South Africa. [6]

Classification

Life restoration of Moschorhinus kitchingi. Moschorhinus DB.jpg
Life restoration of Moschorhinus kitchingi .

The first family-level name used to classify an akidnognathid was Euchambersidae, erected by South African paleontologist Lieuwe Dirk Boonstra in 1934, [7] in reference for the genus Euchambersia , which is possibly one of the oldest known venomous tetrapods. [8] Noting that the taxon is written in improper Latin, German paleontologist Friedrich von Huene changed the spelling of the name to Euchambersiidae in 1940. [9] The taxon Akidnognathidae was first named in 1954 by South African paleontologists Haughton and Adrian Smuts Brink, [10] basing their proposal on Akidnognathinae, which was created in 1928 by Ferenc Nopcsa. Nopcsa originally established Akidnognathinae as a subfamily of the Scaloposauridae, [11] which currently appears to be a wastebasket taxon. In the classification of Haughton and Brink, the akidnognathids includes several therocephalians still recognized as such as well as several other genera, now classified as scylacosaurids. [12] English and American paleontologists D. M. S. Watson and Alfred Romer moved many of these therocephalians into the family Whaitsiidae in 1956, [13] although many were moved back to Akidnognathidae in later years. [14] [15] [12]

In 1974, Christiane Mendrez established the family Moschorhinidae, while recognizing three subfamilies making it up, namely Annatherapsidinae, Moschorhininae and Euchambersiinae. [14] In 1975, the same author proposed another name to designate the group, Annatherapsididae, although she maintained the validity of the three subfamilies previously cited. [16] In their phylogenetic revision of therapsids published in 1986, James Hopson and Herb Barghusen supported Mendrez's hypothesis that the group included three subfamilies, but both authors preferred to use the name Euchambersiidae instead. [17] While the name Euchambersiidae may have priority over Akidnognathidae because it was named first, Akidnognathidae is currently considered as the valid name because it is based on the first named genus of the group, Akidnognathus , this latter having been named in 1918 while Euchambersia was named in 1931. [12] It is on the basis of this affirmation that this name has achieved wider acceptance within the scientific literature. [18] [19] [12] In 1974, Leonid Petrovich Tatarinov proposed uniting the Akidnognathidae (then named Annatherapsididae), the Whaitsiidae and the Moschowhaitsiidae within a superfamily called Whaitsioidea. [20] Multiple authors have disagreed with this proposition, [14] [17] [21] but others like Mikhail Ivakhnenko in 2008 and Adam Huttenlocker in 2009, share Tatarinov's point of view. [22] [12] However, phylogenies led by Huttenlocker and Christian Sidor found that the Akidnognathidae was instead closest to the Chthonosauridae, with the two forming the sister group to the group containing the Whaitsioidea and the Baurioidea. [23] Subsequent classifications published after this study tend to follow this pattern. [6]

The cladogram below follows a phylogenetic analysis led by Jun Liu and Fernando Abdala in 2022, [6] largely sharing the topology recovered by Huttenlocker and Sidor: [23]

Therocephalia

Distribution

Akidnognathids are known from various fossils identified in Russia, South Africa and China. However, a skull from an undescribed taxon was identified in the Fremouw Formation, Antarctica, and is dated to the Lower Triassic. [24]

Related Research Articles

<span class="mw-page-title-main">Therapsida</span> Clade of tetrapods including mammals

Therapsida is a clade comprising a major group of eupelycosaurian synapsids that includes mammals and their ancestors and close relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more underneath the body, resulting in a more "standing" quadrupedal posture, as opposed to the lower sprawling posture of many reptiles and amphibians.

<span class="mw-page-title-main">Therocephalia</span> Extinct order of therapsids

Therocephalia is an extinct clade of eutheriodont therapsids from the Permian and Triassic periods. The therocephalians ("beast-heads") are named after their large skulls, which, along with the structure of their teeth, suggest that they were carnivores. Like other non-mammalian synapsids, therocephalians were once described as "mammal-like reptiles". Therocephalia is the group most closely related to the cynodonts, which gave rise to the mammals, and this relationship takes evidence in a variety of skeletal features. Indeed, it had been proposed that cynodonts may have evolved from therocephalians and so that therocephalians as recognised are paraphyletic in relation to cynodonts.

<i>Trochosaurus</i> Extinct genus of therapsids from Permian South Africa

Trochosaurus is a dubious genus of therocephalian therapsid from South Africa based upon specimens of Lycosuchidae. Three species of Trochosaurus have appeared in literature, T. intermedius, T. major, and T. dirus. The genus Trochosaurus and all three species are considered nomen dubia today, while the specimens referred to them are regarded as Lycosuchidae incertae sedis.

<span class="mw-page-title-main">Eutherocephalia</span> Extinct clade of therapsids

Eutherocephalia is an extinct clade of advanced therocephalian therapsids. Eutherocephalians are distinguished from the lycosuchids and scylacosaurids, two early therocephalian families. While lycosuchids and scyalosaurids became extinct by the end of the Permian period, eutherocephalians survived the Permian–Triassic extinction event. The group eventually became extinct in the Middle Triassic.

<i>Euchambersia</i> Extinct genus of therapsid from Late Permian South Africa

Euchambersia is an extinct genus of therocephalian therapsids that lived during the Late Permian in what is now South Africa and China. The genus contains two species. The type species E. mirabilis was named by paleontologist Robert Broom in 1931 from a skull missing the lower jaw. A second skull, belonging to a probably immature individual, was later described. In 2022, a second species, E. liuyudongi, was named by Jun Liu and Fernando Abdala from a well-preserved skull. It is a member of the family Akidnognathidae, which historically has also been referred by as the synonymous Euchambersiidae.

<i>Moschorhinus</i> Genus of synapsid from late Permian and early Triassic South Africa

Moschorhinus is an extinct genus of therocephalian synapsid in the family Akidnognathidae with only one species: M. kitchingi, which has been found in the Late Permian to Early Triassic of the South African Karoo Supergroup. It was a large carnivorous therapsid, reaching 1.1–1.5 metres (3.6–4.9 ft) in total body length with the largest skull comparable to that of a lion in size, and had a broad, blunt snout which bore long, straight canines.

<i>Lycosuchus</i> Extinct genus of therapsids from the middle Permian of South Africa

Lycosuchus is an extinct genus of carnivorous therocephalians which lived in the Middle Permian 265—260 Ma existing for approximately 5 million years. As a member of the Lycosuchidae, the genus represents one of the earliest diverging therocephalians. The type and only species, L. vanderrieti, is known from a handful of well-preserved specimens featuring the cranium and lower jaw; the holotype US D173 housed at the University of Stellenbosch, South Africa, is a near complete occluded skull. Specimen MB.R. 995, housed at the Museum für Naturkunde Berlin, Germany, consists of a near complete and isolated lower jaw, along with a partial snout and brain case. With the help of μCT data, Pusch et al (2020) described the endocranial anatomy of Lycosuchus vanderrieti.

<i>Theriognathus</i> Extinct genus of therapsids from late Permian South Africa and Tanzania

Theriognathus is an extinct genus of therocephalian therapsid belonging to the family Whaitsiidae, known from fossils from South Africa, Zambia, and Tanzania. Theriognathus has been dated as existing during the Late Permian. Although Theriognathus means mammal jaw, the lower jaw is actually made up of several bones as seen in modern reptiles, in contrast to mammals. Theriognathus displayed many different reptilian and mammalian characteristics. For example, Theriognathus had canine teeth like mammals, and a secondary palate, multiple bones in the mandible, and a typical reptilian jaw joint, all characteristics of reptiles. It is speculated that Theriognathus was either carnivorous or omnivorous based on its teeth, and was suited to hunting small prey in undergrowth. This synapsid adopted a sleek profile of a mammalian predator, with a narrow snout and around 1 meter long. Theriognathus is represented by 56 specimens in the fossil record.

<i>Moschowhaitsia</i> Extinct genus of therapsid from the late Permian of Eurasia

Moschowhaitsia is an extinct genus of therocephalian therapsids from the Late Permian (Guadalupian) of Russia and China. The type species, Moschowhaitsia vjuschkovi, was discovered in the Changxingian-aged Archosaurus Assemblage Zone of Russia and named in 1963 by Russian palaeontologist Leonid Petrovich Tatarinov. A second species was discovered in Jingtai County of Gansu, China in 2020 and named as M. lidaqingi in 2023 by Jun Liu and Fernando Abdala, the first whaitsiid therocephalian to be discovered in China. It was among the larger carnivores in the faunal assemblages it occurred in, with a skull-length of up to 25 centimetres (9.8 in) in M. vjuschkovi and an even larger estimated 35 centimetres (14 in) for M. lidaqingi, one of the largest therocephalian skulls reported. The genus name Moschowhaitsia alludes to two other therocephalians, Moschorhinus and Whaitsia, due to the structure of its palate combining physical features of both these genera.

<i>Megawhaitsia</i> Extinct genus of large therapsids from the Late Permian in East Russia

Megawhaitsia is an extinct genus of large therocephalian therapsids who lived during the Late Permian (Wuchiapingian) in what is now Eastern Europe. The only known species is M. patrichae, described in 2008 from several fossils discovered in various oblasts of European Russia. The fossils are representative of a large animal whose skull size is estimated to be 40–50 cm (16–20 in) long.

Promoschorhynchus is a genus of akidnognathid therocephalians from the Late Permian and Early Triassic of South Africa. Unlike many other therapsids, Promoschorhynchus survived the Permian-Triassic extinction event.

<i>Scymnosaurus</i> Extinct genus of therapsids from middle Permian South Africa

Scymnosaurus is a dubious genus of therocephalian therapsids based upon various fossils of large early therocephalians. The genus was described by Robert Broom in 1903 with S. ferox, followed by S. watsoni in 1915 and a third, S. major, by Lieuwe Dirk Boonstra in 1954. Each of these species are considered nomen dubia today and based upon specimens belonging to two separate families of therocephalians. S. ferox and S. major represent specimens of Lycosuchidae incertae sedis, while S. watsoni is Scylacosauridae incertae sedis. Broom named a fourth species in 1907 from KwaZulu-Natal, S. warreni, though he later referred it to Moschorhinus as a valid species in 1932 but now is recognised as being synonymous with M. kitchingi.

<span class="mw-page-title-main">Baurioidea</span> Extinct superfamily of therapsids

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. S. Watson and Alfred Romer in 1956, is a junior synonym of Baurioidea.

Olivierosuchus is an extinct genus of therocephalian therapsids. It is a member of the family Akidnognathidae. Fossils of Olivierosuchus have been found from the Early Triassic Lystrosaurus Assemblage Zone in South Africa. Unlike other akidnognathids such as Moschorhinus, it has a narrow snout and fewer postcanine teeth. As a distinguishing feature, Olivierosuchus also has a sharp ridge near the choana, an opening in the skull palate. Bumps and projections cover the pterygoid, a bone that forms part of the palate.

<i>Blattoidealestes</i> Extinct genus of therapsid from Middle-Permian South Africa

Blattoidealestes is an extinct genus of therocephalian therapsid from the Middle Permian of South Africa. The type species Blattoidealestes gracilis was named by South African paleontologist Lieuwe Dirk Boonstra from the Tapinocephalus Assemblage Zone in 1954. Dating back to the Middle Permian, Blattoidealestes is one of the oldest therocephalians. It is similar in appearance to the small therocephalian Perplexisaurus from Russia, and may be closely related.

Scalopodon is an extinct genus of therocephalian therapsids from the Late Permian of Russia. The type species Scalopodon tenuisfrons was named in 1999 from the Kotelnichsky District of Kirov Oblast. Scalopodon is known from a single fragmentary holotype specimen including the back of the skull, the left side of the lower jaw and isolated postorbital and prefrontal bones. The skull was found in the Deltavjatia Assemblage Zone, which dates back to the early Wuchiapingian about 260 million years ago. Distinguishing features of Scalopodon include narrow frontal bones and a distinctive sagittal crest along the parietal region at the back of the skull. Scalopodon was originally classified in the family Scaloposauridae, and was the first scaloposaurid found in Russia. More recent studies of therocephalians have found scaloposaurids like Scalopodon to be juvenile forms of larger therocephalians and do not consider Scaloposauridae to be a valid group. Scalopodon and most other scaloposaurids are now classified as basal members of Baurioidea.

Lycideops is an extinct genus of therocephalians from the Late Permian of South Africa. The type species is Lycideops longiceps, named in 1931 by South African paleontologist Robert Broom. Fossils of Lycideops come from the Dicynodon Assemblage Zone of the Beaufort Group. Lycideops is a member of the family Lycideopidae. Like other lycideopids, Lycideops has a long snout.

<i>Urumchia</i> Extinct genus of therapsids from the Early Triassic of China

Urumchia is an extinct genus of therocephalian therapsids from the Early Triassic of China. The type species Urumchia lii was described by Chinese paleontologist C. C. Young in 1952 from the Jiucaiyuan Formation in Xinjiang. The holotype skull has been lost, but Young was able to describe the species on the basis of a detailed cast of the skull. Urumchia is similar to the South African therocephalian Regisaurus in having an expanded pair of vomer bones on the underside of the skull that form a secondary palate. In Urumchia the front end of the vomers narrow to a point, while in Regisaurus they do not. Urumchia has six incisors on either side of the upper jaw, a primitive condition among baurioid therocephalians that usually have fewer incisors.

Simorhinella is an extinct genus of therocephalian therapsids from the Late Permian of South Africa. It is known from a single species, Simorhinella baini, named by South African paleontologist Robert Broom in 1915. Broom named it on the basis of a single fossil collected by the British Museum of Natural History in 1878 that included the skull and jaws forward from the eye sockets. The skull is unusual in that it has an extremely short and deep snout, unlike the longer and lower snouts of most other therocephalians. Because of the skull's distinctiveness, the classification of Simorhinella within Therocephalia is uncertain. However, a 2014 study proposed that it was closely related to the basal therocephalian Lycosuchus, placing it in the family Lycosuchidae.

Ichibengops is an extinct genus of therocephalian therapsids known from the type species Ichibengops munyamadziensis, which lived in what is now Zambia during the Late Permian. Ichibengops was named in 2015 on the basis of fossils found in the Wuchiapingian-age Madumabisa Mudstone Formation in the Luangwa Basin. Therocephalians have been known from the Luangwa Basin for decades, yet Ichibengops was the first endemic Zambian therocephalian to have been described in detail. Phylogenetic analysis indicates that it is a basal member of the clade Eutherocephalia, lying just outside a clade containing hofmeyriids, whaitsiids, and baurioids. Ichibengops is the sister taxon of the Russian therocephalian Chthonosaurus; together they form one of several known African-Russian sister taxon pairs of eutherocephalians, which indicate that eutherocephalians could freely disperse across most of Pangea during the Late Permian. Like the fellow therocephalian Euchambersia, Ichibengops might have had venom glands, as evidenced by grooves above its teeth.

References

  1. ↑ Amalitzky, V. (1922). "Diagnoses of the new forms of vertebrates and plants from the Upper Permian on North Dvina". Bulletin de l'Académie des Sciences de Russie. 16 (6): 329–340.
  2. 1 2 3 Liu, J.; Abdala, F. (2017). "The tetrapod fauna of the upper Permian Naobaogou Formation of China: 1. Shiguaignathus wangi gen. et sp. nov., the first akidnognathid therocephalian from China". PeerJ . 5: e4150. doi: 10.7717/peerj.4150 . PMC   5723136 . PMID   29230374.
  3. ↑ Haughton, S. H. (1918). "Some new carnivorous Therapsida, with notes upon the braincase in certain species". Annals of the South African Museum . 12: 175–216.
  4. ↑ Smith, R.; Rubidge, B.; van der Walt, M. (2011), "Therapsid Biodiversity Patterns and Palaeoenvironments of the Karoo Basin, South Africa", in Chinsamy-Turan, A. (ed.), Forerunners of Mammals: Radiation, Histology, Biology, Bloomington: Indiana University Press, pp. 31–64, ISBN   978-0-253-00533-5
  5. ↑ Liu, J.; Abdala, F. (2019). "The tetrapod fauna of the upper Permian Naobaogou Formation of China: 3. Jiufengia jiai gen. et sp. nov., a large akidnognathid therocephalian". PeerJ . 7: e6463. doi: 10.7717/peerj.6463 . PMC   6388668 . PMID   30809450.
  6. 1 2 3 4 Liu, J.; Abdala, F. (2022). "The emblematic South African therocephalian Euchambersia in China: a new link in the dispersal of late Permian vertebrates across Pangea". Biology Letters . 18 (7): 20220222. doi: 10.1098/rsbl.2022.0222 . PMC   9278400 . PMID   35857894.
  7. ↑ Boonstra, L. D. (1934). "A contribution to the morphology of the mammal-like reptiles of the suborder Therocephalia". Annals of the South African Museum . 31: 215–267.
  8. ↑ Benoit, J.; Norton, L. A.; Manger, P. R.; Rubidge, B. S. (2017). "Reappraisal of the envenoming capacity of Euchambersia mirabilis (Therapsida, Therocephalia) using μCT-scanning techniques". PLOS ONE . 12 (2): e0172047. Bibcode:2017PLoSO..1272047B. doi: 10.1371/journal.pone.0172047 . PMC   5302418 . PMID   28187210.
  9. ↑ von Huene, F. (1940). "Die Saurier der Karroo, Gondwana und verwandten Ablagerungen in faunistischer, biologischer und phylogenetischer Hinsicht" [The reptiles of the Karroo, Gondwana and related deposits in faunistic, biological and phylogenetic terms]. Neues Jahrbuch für Mineralogie, Geologie und Paläontologie, Beilage-Band (in German). 83: 246–347. OCLC   600936687.
  10. ↑ Haughton, S. H.; Brink, A. S. (1954). "A bibliographical list of Reptilia from the Karroo beds of Africa". Palaeontologia Africana. 2: 1–187.
  11. ↑ Nopcsa, F. (1928). "The genera of reptiles" (PDF). Palaeobiologica. 1: 163–188.
  12. 1 2 3 4 5 Huttenlocker, A. (2009). "An investigation into the cladistic relationships and monophyly of therocephalian therapsids (Amniota: Synapsida)". Zoological Journal of the Linnean Society . 157 (4): 865–891. doi: 10.1111/j.1096-3642.2009.00538.x . S2CID   84603632.
  13. ↑ Watson, D. M. S.; Romer, A. S. (1956). "A classification of therapsid reptiles". Bulletin of the Museum of Comparative Zoology . 111: 37–89. OCLC   249699529.
  14. 1 2 3 Mendrez, C. H. (1974). "Étude du crâne d'un jeune spécimen de Moschorhinus kitchingi Broom, 1920 (?Tigrisuchus simus Owen, 1876), Therocephalia, Pristerosauria, Moschorhinidae d'Afrique Australe (Remarques sur les Moschorhinidae et les Whaitsiidae)" [Study of the skull of a young specimen of Moschorhinus kitchingi Broom, 1920 (?Tigrisuchus simus Owen, 1876), Therocephalia, Pristerosauria, Moschorhinidae from Southern Africa (Remarks on Moschorhinidae and Whaitsiidae)]. Annals of the South African Museum (in French). 64: 71–115.
  15. ↑ Durand, J. F. (1991). "A revised description of the skull of Moschorhinus (Therapsida, Therocephalia)". Annals of the South African Museum . 99: 381–413.
  16. ↑ Mendrez, C. H. (1975). "Principales variations du palais chez les thérocéphales Sud-Africains (Pristerosauria et Scaloposauria) au cours du Permien Supérieur et du Trias Inférieur" [Main variations of the palate in South African therocephalians (Pristerosauria and Scaloposauria) during the Upper Permian and Lower Triassic]. Colloque International C.N.R.S. Problèmes Actuels de Paléontologie-Évolution des Vertébrés (in French). 218: 379–408.
  17. 1 2 Hopson, J. A.; Barghusen, H. R. (1986), "An analysis of therapsid relationships", in Hotton III, N.; MacLean, P. D.; Roth, J. J.; Roth, E. C. (eds.), The Ecology and Biology of Mammal-like Reptiles, Washington, D. C.: Smithsonian Institution Press, pp. 83–106, ISBN   978-0-874-74519-1, JSTOR   4523181
  18. ↑ Rubidge, B. S.; Sidor, C. A. (2001). "Evolutionary Patterns Among Permo-Triassic Therapsids". Annual Review of Ecology and Systematics . 32: 449–480. doi:10.1146/annurev.ecolsys.32.081501.114113. S2CID   51563288.
  19. ↑ Sigurdsen, T. (2006). "New features of the snout and orbit of a therocephalian therapsid from South Africa" (PDF). Acta Palaeontologica Polonica . 51 (1): 63–75.
  20. ↑ Tatarinov, L. P. (1974). Териодонты СССР [Theriodonts of the USSR] (in Russian). Vol. 143. Trudy Paleontologicheskogo Instituta, Akademiya Nauk SSSR. pp. 1–226.
  21. ↑ Huttenlocker, A. K.; Smith, R. M. H. (2017). "New whaitsioids (Therapsida: Therocephalia) from the Teekloof Formation of South Africa and therocephalian diversity during the end-Guadalupian extinction". PeerJ . 5: e3868. doi: 10.7717/peerj.3868 . PMC   5632541 . PMID   29018609.
  22. ↑ Ivakhnenko, M. F. (2008). "The First Whaitsiid (Therocephalia, Theromorpha)". Paleontological Journal . 42 (4): 409–413. doi:10.1134/S0031030108040102. S2CID   140547244.
  23. 1 2 Huttenlocker, A. K.; Sidor, C. A. (2016). "The first karenitid (Therapsida, Therocephalia) from the upper Permian of Gondwana and the biogeography of Permo-Triassic therocephalians". Journal of Vertebrate Paleontology . 36 (4): e1111897. Bibcode:2016JVPal..36E1897H. doi:10.1080/02724634.2016.1111897. JSTOR   24740259. S2CID   130994874.
  24. ↑ Huttenlocker, A. K.; Sidor, C. A. (2012). "Taxonomic Revision of Therocephalians (Therapsida: Theriodontia) from the Lower Triassic of Antarctica". American Museum Novitates . 3728: 1–19. doi: 10.1206/3738.2 . S2CID   55745212.
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