Triconodontids can be distinguished from other eutriconodonts by the shape of theirmolars, which bore three maincusps of roughly equal size. Duringocclusion, the upper and lower molars interlocked tightly, producing a self-sharpening cutting edge. Historically, the triconodontids were thought to have a different occlusion pattern than other eutriconodonts, with the middle cusp of the lower molar (cusp a) fitting between the middle cusp (cusp A) and the front cusp (cusp B) of the upper molar, as in the basalmammaliaformMorganucodon.[4] However, a 2020 study onPriacodon suggests that triconodontids occluded their molars in the same manner as other eutriconodonts (so-called "embrasure occlusion"), with the middle cusp (cusp A/a) fitting between two opposing molars.[5]
Triconodontidae was named by Marsh (1887). It was assigned toPolyprotodontia by Cope (1889); toTriconodonta by Rasmussen and Callison (1981), Bonaparte (1986), Carroll (1988) and Engelmann and Callison (1998); and toMammalia by Marsh (1887) and Luoet al. (2001).[6]
SometimesVolaticotheria is recovered as a part of this group.[2] However, other phylogenetic studies group it outside of Triconodontidae.[7][8]
^abBajpai, Sunil; Rautela, Abhay; Yadav, Ravi; Mantilla, Gregory P. Wilson (29 February 2024). "The first eutriconodontan mammal from the Cretaceous (Maastrichtian) of India".Journal of Vertebrate Paleontology.43 (4).doi:10.1080/02724634.2024.2312234.
^Gaetano, L. C.; Rougier, G. W. (2012). "First Amphilestid from South America: A Molariform from the Jurassic Cañadón Asfalto Formation, Patagonia, Argentina".Journal of Mammalian Evolution.19 (4):235–248.doi:10.1007/s10914-012-9194-1.hdl:11336/68489.S2CID254698557.
^Averianov, A. O.; Lopatin, A. V. (2011). "Phylogeny of triconodonts and symmetrodonts and the origin of extant mammals".Doklady Biological Sciences.436 (1):32–35.doi:10.1134/s0012496611010042.PMID21374009.S2CID10324906.
