Skull of Diademodon mastacus on display at the Museum für Naturkunde, Berlin, photographed by FunkMonk.

Belongs within: Eutherapsida.
Contains: Mammaliaformes.

The clade Cynodontia, incluing modern mammals and a number of related non-mammalian synapsids, was defined by Hopson & Kitching (2001) as the most inclusive clade including Mammalia and excluding Bauria. Though the group was ancestrally carnivorous, herbivory evolved among the cynodonts in the Gomphodontia and the Tritylodontidae (as well as several times within the mammals). Cynodonts are first known from the Late Permian, where they are represented by Dvinia and the Procynosuchidae. The remaining cynodonts form a clade Epicynodontia, defined as all taxa closer to mammals than Procynosuchidae and united by synapomorphies including a dentary-surangular dorsal contact midway between the postorbital bar and jaw joint, a coronoid process on the dentary extending above the middle of the orbit, four upper incisors and three lower incisors (Hopson & Kitching 2001).

Characters (from Hopson & Kitching 2001): Nasal-lacrimal contact present; postfrontal absent; prefrontal-postorbital contact present; ectopterygoid not in contact with maxilla; palatal exposure of maxilla behind canine greater than 20% distance from canine to posterior end of palatine; secondary palatal plate on maxilla and palatine; pterygoid flange without teeth; tabular extending around posttemporal foramen; groove on prootic extending from pterygoparoccipital foramen to trigemimal foramen; trigeminal nerve exiting via foramen between prootic and epipterygoid; posteroventral process on quadrate in posterior notch of squamosal; ascending process of epipterygoid greatly expanded; epipterygoid overlapping prootic; lateral flange present on prootic; epipterygoid in contact with frontal; double occipital condyles; stapedial foramen with dorsoventral orientation; dentary masseteric fossa present high on coronoid region; dentary overlap of surangular long; reflected lamina of angula spoon-shaped plate; incisor cutting margins smoothly ridged; canine serrations absent; postcanines with two or more cusps in line; lower anterior cingulum or cusp present; anterior process of ilium 1.0 to 1.5 times diameter of acetabulum; pubis between 1.5 and 1.0 times acetabular diameter.

    |  i. s.: Chaliminia LCS01
    |         Lepagia DDL04
    |         Chronoperates paradoxus Fox, Youzwyshyn & Krause 1992 SFY02
    |--Dvinia HK01
    `--+--Procynosuchidae TT05
       |    |--Uralocynodon tverdochlebovae (Tatarinov 1987) TT05
       |    `--Procynosuchus Broom 1931 MH06, D07
       |         |--P. delaharpeae D07
       |         `--P. rubidgei D07
       `--Epicynodontia HK01
            |--Galesaurus HK01
            `--+--Thrinaxodon Seeley 1894 MH06, D07 [Thrinaxodontidae]
               |    `--T. liorhinus HK01
               `--Eucynodontia [Mammaliamorpha, Tritylodontoidea] HK01
                    |--Cynognathia HK01
                    |    |--Cynognathus Seeley 1895 HK01, D07 [Cynognathidae]
                    |    |    `--C. crateronotus HK01
                    |    `--Gomphodontia [Diademodontidae] HK01
                    |         |--Diademodon mastacus HK01
                    |         `--+--Trirachodon HK01
                    |            `--+--Pascualgnathus HK01
                    |               `--+--Scalenodon angustifrons HK01
                    |                  `--+--Luangwa HK01
                    |                     `--Traversodontidae D07
                    |                          |--Massetognathus Romer 1967 HK01, D07
                    |                          |    |--M. ochagaviae D07
                    |                          |    `--M. pascuali D07
                    |                          `--+--‘Scalenodon’ hirschoni HK01
                    |                             `--+--Exaeretodon HK01
                    |                                `--Gomphodontosuchus HK01
                    `--Probainognathia HK01
                         |--Lumkuia Hopson & Kitching 2001 [Lumkuiidae] HK01
                         |    `--*L. fuzzi Hopson & Kitching 2001 HK01
                         `--+--Ecteninion HK01
                            `--+--+--Probainognathus [Probainognathidae] LY11
                               |  |    `--P. jenseni HK01
                               |  `--+--Pachygenelus [Tritheledontidae] LY11
                               |     |    `--P. monus Watson 1913 OB13
                               |     `--+--Mammaliaformes LY11
                               |        |--+--Brasilodon MH06
                               |        |  `--Brasilitherium MH06
                               |        `--Tritylodontidae LY11
                               |             |  i. s.: Tritylodon longaevus Owne 1884 OB13
                               |             |--Kayentatherium KH14
                               |             |--Yunnanodon KH14
                               |             |--+--Bienotherium KH14
                               |             |  `--Oligokyphus Hennig 1922 KH14, D07
                               |             |       |--O. major [incl. O. minor] D07
                               |             |       `--O. triserialis D07
                               |             `--+--Bocatherium KH14
                               |                `--Bienotheroides KH14
                               `--Chiniquodontoidea DDL04
                                    |--Chiniquodontidae HK01
                                    |    |--Probelesodon HK01
                                    |    `--+--Aleodon brachyrhamphus HK01, NS10
                                    |       `--Chiniquodon von Huene 1936 MH06, D07
                                    |            |--C. magnificus D07
                                    |            |--C. sanjuanensis D07
                                    |            `--C. theotonicus D07
                                    `--+--+--Therioherpeton DDL04
                                       |  `--Charruodon DDL04
                                       `--Dromatheriidae DDL04
                                            |--Microconodon tenuirostris [=Dromatherium tenuirostris] DDL04
                                            |--Tricuspes DDL04
                                            |--Meurthodon DDL04
                                            |--Rewaconodon Datta, Das & Luo 2004 DDL04
                                            |    `--*R. tikiensis Datta, Das & Luo 2004 DDL04
                                            `--Pseudotriconodon DDL04
                                                 |--P. chatterjeei Lucas & Oakes 1988 DDL04
                                                 `--P. wildi DDL04

*Type species of generic name indicated


[DDL04] Datta, P. M., D. P. Das & Z.-X. Luo. 2004. A Late Triassic dromatheriid (Synapsida: Cynodontia) from India. Annals of Carnegie Museum 73 (2): 12–24.

[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.

[HK01] Hopson, J. A., & J. W. Kitching. 2001. A probainognathian cynodont from South Africa and the phylogeny of nonmammalian cynodonts. Bulletin of the Museum of Comparative Zoology 156 (1): 5–35.

[KH14] Krause, D. W., S. Hoffmann, J. R. Wible, E. C. Kirk, J. A. Schultz, W. von Koenigswald, J. R. Groenke, J. B. Rossie, P. M. O'Connor, E. R. Seiffert, E. R. Dumont, W. L. Holloway, R. R. Rogers, L. J. Rahantarisoa, A. D. Kemp & H. Andriamialison. 2014. First cranial remains of a gondwanatherian mammal reveal remarkable mosaicism. Nature 515: 512–517.

[LCS01] Luo, Z.-X., A. W. Crompton & A.-L. Sun. 2001. A new mammaliaform from the Early Jurassic and evolution of mammalian characteristics. Science 292: 1535–1540.

[LY11] Luo, Z.-X., C.-X. Yuan, Q.-J. Meng & Q. Ji. 2011. A Jurassic eutherian mammal and divergence of marsupials and placentals. Nature 476: 442–445.

[MH06] Meng, J., Y. Hu, Y. Wang, X. Wang & C. Li. 2006. A Mesozoic gliding mammal from northeast China. Nature 444 (7121): 889–893.

[NS10] Nesbitt, S. J., C. A. Sidor, R. B. Irmis, K. D. Angielczyk, R. M. H. Smith & L. A. Tsuji. 2010. Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira. Nature 464: 95–98.

[OB13] O'Leary, M. A., J. I. Bloch, J. J. Flynn, T. J. Gaudin, A. Giallombardo, N. P. Giannini, S. L. Goldberg, B. P. Kraatz, Z.-X. Luo, J. Meng, X. Ni, M. J. Novacek, F. A. Perini, Z. S. Randall, G. W. Rougier, E. J. Sargis, M. T. Silcox, N. B. Simmons, M. Spaulding, P. M. Velazco, M. Weksler, J. R. Wible & A. L. Cirranello. 2013. The placental mammal ancestor and the post-K–Pg radiation of placentals. Science 339: 662–667.

[SFY02] Scott, C. S., R. C. Fox & G. P. Youzwyshyn. 2002. New earliest Tiffanian (late Paleocene) mammals from Cochrane 2, southwestern Alberta, Canada. Acta Palaeontologica Polonica 47: 691–704.

[TT05] Tverdokhlebov, V. P., G. I. Tverdokhlebova, A. V. Minikh, M. V. Surkov & M. J. Benton. 2005. Upper Permian vertebrates and their sedimentological context in the South Urals, Russia. Earth-Science Reviews 69: 27–77.

Last updated: 24 August 2018.

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