Eucynodontia

Eucynodontia ("true dog teeth") is a clade of cynodont therapsids including mammals and most non-mammalian cynodonts. The oldest eucynodonts are known from the Early Triassic and possibly Late Permian. Eucynodontia includes two major subgroups, Cynognathia and Probainognathia.^[1]

Eucynodonts Temporal range: Early Triassic-Holocene, 251–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Examples of eucynodonts. 1st row: Trirachodon berryi, Probainognathus jenseni; 2nd row: Brasilitherium riograndensis, Castorocauda lutrasimilis; 3rd row: Ornithorhynchus anatinus (platypus), Loxodonta africana (African bush elephant).
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Synapsida
Clade:	Therapsida
Clade:	Cynodontia
Clade:	Epicynodontia
Clade:	Eucynodontia Kemp, 1982
Subgroups
†Kataigidodon †Cynognathia Probainognathia

The clade was named in 1982 by Thomas Kemp, who defined it as all cynodonts more derived than Thrinaxodon.^[2][3]

In 2001, Hopson and Kitching redefined the clade Eucynodontia as the least inclusive group containing Mammalia and Exaeretodon.^[4]

Phylogeny

Cladogram after Stefanello et al. (2023):^[5]

	Procynosuchus
	Galesaurus Thrinaxodon Platycraniellus Eucynodontia Cynognathia Cynognathus Gomphodontia Diademodon Langbergia Trirachodon Sinognathus Traversodontidae Pascualgnathus Luangwa Scalenodon Mandagomphodon Massetognathus Exaeretodon Probainognathia Lumkuia Chiniquodon Probainognathidae Probainognathus Bonacynodon Ecteniniidae Trucidocynodon Ectenion (sic) Diegocanis Protheriodon Prozostrodontia Prozostrodontidae Prozostrodon Pseudotherium Therioherpeton Irajatherium Riograndia Diarthrognathus Pachygenelus Tritylodontidae Botucaraitherium Brasilodon Mammaliaformes

References

1. Rubidge, B.S.; Sidor, C.A. (2001). "Evolutionary patterns among Permo-Triassic therapsids" (PDF). Annual Review of Ecology, Evolution, and Systematics. 32: 449–480. doi:10.1146/annurev.ecolsys.32.081501.114113. Archived from the original (PDF) on 2012-03-21.
2. T.S. Kemp. 1982. Mammal-like Reptiles and the Origin of Mammals 363 pp
3. Martínez, R. N.; Fernandez, E.; Alcober, O. A. (2013). "A new non-mammaliaform eucynodont from the Carnian-Norian Ischigualasto Formation, Northwestern Argentina". Revista Brasileira de Paleontologia. 16: 61–76. doi:10.4072/rbp.2013.1.05.
4. James A. Hopson and James W. Kitching, 2001, "A Probainognathian Cynodont from South Africa and the Phylogeny of Nonmammalian Cynodonts" pp 5-35 in: PARISH A. JENKINS, JR., MICHAEL D. SHAPIRO, AND TOMASZ OWERKOWICZ, EDITORS, STUDIES IN ORGANISMIC AND EVOLUTIONARY BIOLOGY IN HONOR OF A. W. CROMPTON Bullettin of the Museum of Comparative Zoology. Harvard University 156(1)
5. Stefanello, M.; Martinelli, A. G.; Müller, R. T.; Dias-da-Silva, S.; Kerber, L. (2023). "A complete skull of a stem mammal from the Late Triassic of Brazil illuminates the early evolution of prozostrodontian cynodonts". Journal of Mammalian Evolution. doi:10.1007/s10914-022-09648-y.