The oldest eucynodonts are known from the Early Triassic and possibly Late Permian.

Eucynodontia includes two major subgroups, Cynognathia and Probainognathia.

[1] 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] Cladogram after Stefanello et al. (2023):[5] Procynosuchus Galesaurus Thrinaxodon Platycraniellus Cynognathus Diademodon Langbergia Trirachodon Sinognathus Pascualgnathus Luangwa Scalenodon Mandagomphodon Massetognathus Exaeretodon Lumkuia Chiniquodon Probainognathus Bonacynodon Trucidocynodon Ectenion (sic) Diegocanis Protheriodon Prozostrodon Pseudotherium Therioherpeton Irajatherium Riograndia Diarthrognathus Pachygenelus Tritylodontidae Botucaraitherium Brasilodon Mammaliaformes