Trituberculata

The Trituberculata is an extinct group of mammals in the fossil record from about 215–85 illion years ago (mya). The discoveries were isolated teeth, so not much else can be said about the animals. They were small insectivores, and probably nocturnal.Kermack K.A; Lees, Patricia M. & Mussett, Frances 1965. Aegialodon dawsoni: a new trituberculosectorial tooth from the Lower Wealden.
Proceedings of the Royal Society of London. Series B, Biological Sciences
 162, 989, 535-554. Gerkema M.P. et al 2013. The nocturnal bottleneck and the evolution of activity patterns in mammals. Proceedings of the Royal Society B: Biological Sciences 280 (1765).   The group contains the ancestors of Placentalia and Marsupialia; all modern mammals except Monotremes are descended from trituberculates.

The name comes from the three tubercles (cusps) of the molar teeth (not to be confused with Triconodonta). The clade Trituberculata is not always regarded as valid. They probably do not form a monophyletic group. Instead, some may be "true" basal mammals (though not always closest related to each other). Others (such as the symmetrodonts) may fall just outside the therian crown group.

 References 

 Sources 
Kemp T.S. 2005. The origin and evolution of mammals. Oxford University Press. 
Kermack D.M. & K.A. 1984. The evolution of mammalian characters. London: Croom Helm. 
Kielan-Jaworowska, Zofia; Cifelli, Richard L. & Luo, Zhe-Xi  2004. Mammals from the Age of Dinosaurs: origins, evolution, and structure. Columbia University Press, New York, 2004 .

Category:Extinct mammals
Category:Fossils
Category:Mesozoic