Skull and reproduction of head of Notopithecus, from here.

Belongs within: Pholidotamorpha.
Contains: Toxodontia.

The Notoungulata were a diverse group of herbivorous mammals found in South America from the Palaeocene to the Pleistocene; a single Pleistocene species Mixotoxodon larensis was found in southern North America following the formation of the Central American land bridge. Various forms might be described as convergent on Northern Hemisphere rhinos, pigs, rabbits or hyraxes. The relations of notoungulates within other mammals remain poorly established; various relationships have been suggested with modern afrotherians and euungulates, and it is debated whether or not notoungulates are directly related to other extinct South American ‘ungulates’ such as litopterns or astrapotheres.

Characters (from Rose 2006): Early forms with dental formula of; teeth usually closely spaced, diastema absent; cheek teeth lophodont: upper molars with strong, straight ectoloph, oblique protoloph and more transverse metaloph; tendency to develop extra crests running toward centre of upper molar, including ‘crochet’ extending anterobuccally from metaloph; lower molars with two main crescentic crests, the metalophid and hypolophid, with shorter transverse entolophid derived from entoconid; paraconid typically absent; paracristid short; ectocingulum usually weak or absent on both upper and lower teeth. Skull with postorbital bar absent, zygomatic arch arising high on back of skull. Ear region with tympanic cavity connected to large epitympanic sinus in squamosal, often also to hypotympanic sinus below tympanic cavity; inflated ectotympanic bulla surrounding tympanic cavity, extending laterally as external auditory tube with ventral crest; fossa present behind bulla for projection of the hyoid. Feet mesaxonic; astragalus with moderately long constricted neck, roughly hemispherical head, medial projection on body, prominent dorsal foramen, posterior sulcus, partly confluent sustentacular and navicular facets; astragalar trochlea slightly grooved with high lateral rim; calcaneal peroneal tubercle distally situated.

| i. s.: Pachyrukhos Ameghino 1885D07
| `--P. moyaniD07
| Trigodon Ameghino 1882D07
| `--T. gaudryiD07
| |--HenricosborniidaeSM93
| | |--Othnielmarshia Ameghino 1901SM93
| | |--Henricosbornia Ameghino 1901SM93
| | |--Peripantostylops Ameghino 1904SM93
| | `--Simpsonotus praecursorR06, OB13
| `--NotostylopidaeSM93
| |--Boreastylops Vucetich 1980SM93
| |--Edvardtrouessartia Ameghino 1901SM93
| |--Homalostylops Ameghino 1901SM93
| `--Notostylops Ameghino 1897D07
| |--N. brachycephalusS32
| `--N. escaridusS32
| i. s.: TypotheridaeA05
| |--Isotypotherium annulatumA05
| `--TypotheriumA05
| |--T. cristatumA05
| |--T. insigneA05
| `--T. robustumA05
| Campanorca Bond et al. 1984SM93 [CampanorcidaeR06]
| |--Oldfieldthomasia debilitata [=Acoelodus debilitatus]S32
| |--Colbertia de Paula Couto 1952SM93
| |--Itaboraitherium Paula Couto 1970SM93
| `--Tsamnichoria Simpson 1936SM93
| |--Archaeopithecus Ameghino 1897SM93
| `--Acropithecus Ameghino 1904SM93
| |--Transpithecus Ameghino 1901SM93
| |--Notopithecus [Notopithecidae]R06
| | `--N. adapinusS32
| `--Protypotherium Ameghino 1882SM93
| |--P. anomopodusD07
| |--P. australeD07
| `--P. minitumD07
| | i. s.: Mesotherium Serres 1867SM93
| `--TrachytheriinaeSM93
| |--Ethegotherium Simpson et al. 1962SM93
| `--Paedotherium Burmeister 1888SM93
|--Eohyrax Ameghino 1901SM93
`--Archaeohyrax Ameghino 1897D07
`--A. patagonicusD07

*Type species of generic name indicated


[A05] Ameghino, F. 1905. Les édentés fossiles de France et d’Allemagne. Anales del Museo Nacional de Buenos Aires, serie 3, 6: 175–250.

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

[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.

[R06] Rose, K. D. 2006. The Beginning of the Age of Mammals. John Hopkins University Press: Baltimore.

[S32] Simpson, G. G. 1932. Skulls and brains of some mammals from the Notostylops beds of Patagonia. American Museum Novitates 578: 1–11.

[SM93] Stucky, R. K., & M. C. McKenna. 1993. Mammalia. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 739–771. Chapman & Hall: London.

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