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Tetracynodon - Wikipedia

From Wikipedia, the free encyclopedia

Tetracynodon Temporal range: Late Permian - Early Triassic

Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Synapsida
Clade:	Therapsida
Clade:	†Therocephalia
Family:	†Lycideopidae
Genus:	†Tetracynodon Broom and Robinson, 1948
Species
†T. tenuis Broom and Robinson, 1948 †T. darti Sigogneau, 1963

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 the Early Triassic. Both species were small-bodied and probably fed on insects and small vertebrates. Although Tetracynodon is more closely related to mammals than to reptiles, its braincase is very primitive and more resembles that of modern amphibians and reptiles than of mammals.^[1]

Permo-Triassic survivorship

Tetracynodon was one of the few therapsid genera known to have survived the Permo-Triassic extinction event. Aside from Tetracynodon, the only therocephalian genera known from both sides of the Permo-Triassic boundary are Moschorhinus, Ictidosuchoides and Promoschorhynchus. The Triassic species Tetracynodon darti would have been part of the extinction's survivor fauna, a low-diversity community of therapsids and other land vertebrates. The Triassic species Tetracynodon darti is relatively small compared to Permian baurioids. This may be a possible example of the Lilliput effect in which small species are more common immediately after a mass extinction.^[1]

Phylogeny

Tetracynodon was once classified among a group of therocephalians called scaloposaurids, all characterized by their very small size. Scaloposauridae is no longer recognized as a valid group because many scaloposaurid features are now thought to be characteristics of juvenile individuals rather than evidence of close evolutionary relationships.^[1]

In 2008, Tetracynodon tenuis was proposed to be a juvenile of the larger therocephalian Lycideops, which is known from the same Late Permian strata. Since T. tenuis is the type species of Tetracynodon and the type species of Lycideops, L. longiceps, was named earlier than T. tenuis, the species would be a synonym of Lycideops longiceps and the genus Tetracynodon would be invalid. Moreover, since the study found that Lycideops was not directly related to the Early Triassic Tetracynodon darti, it suggested that this lineage of therocephalians did not survive uninterrupted past the Permo-Triassic extinction event.^[2]

Tetracynodon was included in a phylogenetic analysis of therocephalians in 2012 and was placed in clade Baurioidea along with many other prior scaloposaurids. It was found to nest in a smaller clade with Lycideops and Choerosaurus, designated as the family Lycideopidae. Tetracynodon tenuis and T. darti were found to be sister taxa, meaning that they were a valid phylogenetic grouping and T. tenuis could not be a juvenile of Lycideops. Below is a cladogram from the study:^[1]

Therapsida

Biarmosuchus tener

Titanophoneus potens

Charassognathus gracilis

	Dvinia prima

	Procynosuchus delaharpeae

Therocephalia

Lycosuchus vanderrieti

	Glanosuchus macrops

	Ictidosaurus angusticeps

	Pristerognathus polyodon

Eutherocephalia

Euchambersia mirabilis

	Promoschorhynchus platyrhinus

	Olivierosuchus parringtoni

	Cerdops burgheri

	Moschorhinus kitchingi

Ictidostoma hemburyi

Hofmeyria atavus

Mirotenthes digitipes

Viatkosuchus sumini

	Moschowhaitsia vjuschkovi

	Theriognathus microps

Baurioidea

Ictidosuchus primaevus

Ictidosuchops rubidgei

Ictidosuchoides longiceps

Regisaurus jacobi

Scaloposaurus constrictus

Ericiolacerta parva

Bauriidae

Lycideopidae

Lycideops longiceps

Choerosaurus dejageri

	Tetracynodon tenuis

	Tetracynodon darti

References

^ ^a ^b ^c ^d Sigurdsen, T.; Huttenlocker, A. K.; Modesto, S. P.; Rowe, T. B.; Damiani, R. (2012). "Reassessment of the morphology and paleobiology of the therocephalian Tetracynodon darti (Therapsida), and the phylogenetic relationships of Baurioidea". Journal of Vertebrate Paleontology. 32 (5): 1113. Bibcode:2012JVPal..32.1113S. doi:10.1080/02724634.2012.688693.
^ Kammerer, C. (2008). "A new therocephalian from the Cistecephalus Assemblage Zone of South Africa and new information on therocephalian systematics". Journal of Vertebrate Paleontology. 28 (3, suppl): 98A–99A. doi:10.1080/02724634.2008.10010459.

Therocephalia

Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade: Eutheriodontia

Synapsida

see Synapsida
Therocephalia	see below↓

Therocephalia

Gorynychus Porosteognathus Cynodontia?
Lycosuchidae	Lycosuchus Simorhinella
Scylacosauridae	Alopecodon Alopecognathus Biarmosuchoides? Eutheriodon Glanosuchus Hyorhynchus Julognathus Koksharovia Maraisaurus Pardosuchus Pristerognathus Scylacosaurus

Eutherocephalia

Chthonosauridae

Chthonosaurus
Ichibengops

Akidnognathidae

Whaitsioidea

Ophidostoma
Hofmeyriidae	Gorochovetzia Hofmeyria Ictidostoma Mirotenthes
Whaitsiidae	Dalongkoua Ictidochampsa Megawhaitsia Microwhaitsia Moschowhaitsia Theriognathus Viatkosuchus

Baurioidea

- see below↓

Baurioidea

Karenitidae

Karenites
Mupashi

Lycideopidae

Regisauridae

Regisaurus
Urumchia

Bauriamorpha

Hazhenia Nothogomphodon Notictoides Ordosiodon Scaloposaurus
Ericiolacertidae	Ericiolacerta Pedaeosaurus? Silphedosuchus
Bauriidae	Antecosuchus Bauria Microgomphodon Scalopognathus Traversodontoides

Nomina dubia
Alopecorhinus Arnognathus Blattoidealestes Dongusaurus Hyaenasuchus Ictidoparia Ictidosaurus Scymnosaurus Tamboeria Trochorhinus Trochosaurus Trochosuchus

Category

Geology of South Africa

Geological formations

List of fossiliferous stratigraphic units in South Africa

Palaeoarchaean	Bushveld Igneous Complex Fig Tree Formation Komatii Formation Moodies Group Onverwacht Group Transvaal Supergroup
Paleozoic	Carboniferous Dwyka Group Ganigobis Formation Devonian Bokkeveld Group Table Mountain Sandstone Permian Abrahamskraal Formation Balfour Formation Dwyka Group Ganigobis Formation Teekloof Formation Whitehill Formation Ordovician Soom Shale
Mesozoic	Cretaceous Uitenhage Group Buffelskloof Formation Enon Formation Kirkwood Formation Sundays River Formation Kalahari Deposits Jurassic Drakensberg Group Enon Formation Uitenhage Group Karoo Supergroup Beaufort Group Abrahamskraal Formation Balfour Formation Katberg Formation Middleton Formation Teekloof Formation Dwyka Group Ecca Group Whitehill Formation Stormberg Group Bushveld Sandstone Clarens Formation Elliot Formation Triassic Elliot Formation Katberg Formation Molteno Formation Normandien Formation
Cenozoic	Algoa Group

‎Tectonics and orogeny

Volcanism	List of volcanoes in South Africa Pilanesberg Pilanesberg Game Reserve Prince Edward Islands Diatremes Big Hole Finsch diamond mine Jagersfontein Mine Koffiefontein mine Barberton Greenstone Belt Drakensberg Karoo-Ferrar
Earthquakes	1620 Robben Island earthquake 1969 Tulbagh earthquake 2006 Mozambique earthquake 2014 Orkney earthquake
Impact craters	Kalkkop crater Morokweng impact structure Tswaing crater Vredefort impact structure
Meteorites	Bellsbank meteorite

‎Mineral deposits
Kimberlite Merensky Reef Witwatersrand Banket (mining term) Coal in South Africa Iron ore in Africa Platinum in Africa Titanium in Africa Uranium in Africa Minerals Council South Africa Department of Mineral Resources (South Africa) Department of Mineral Resources and Energy

Paleontology‎

Ordovician

Devonian

Carboniferous

Permian

Beaufort Group

Assemblages	Cistecephalus Assemblage Zone Daptocephalus Assemblage Zone Eodicynodon Assemblage Zone Pristerognathus Assemblage Zone Tapinocephalus Assemblage Zone Tropidostoma Assemblage Zone

Triassic

Assemblages	Cynognathus Assemblage Zone Lystrosaurus Assemblage Zone

Jurassic

Cretaceous

Paleogene

Nummulite

Neogene

Pleistocene

Other

Research and administration‎

Geologists	Hans Merensky
Paleontologists	Andrew Geddes Bain Lieuwe Dirk Boonstra Charles Kimberlin Brain Robert Broom Alfred Brown Anusuya Chinsamy-Turan H. Basil S. Cooke Alfred W. Crompton Daniel Rossouw Kannemeyer Andre Keyser James Kitching John Talbot Robinson George William Stow Eduard Meine van Zinderen-Bakker

Regional articles
Geology of Cape Town

Other
Pothole (geology) Steep structure Swazian

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