PHYLOGENETIC INTEGRITY AND RELATIONSHIPS OF TRICONODONTIDAE (MAMMALIA)

Triconodontids are one of several groups of early mammals characterized by a serially tricuspate molar pattern, believed to be primitive for Mammalia (and therefore uninformative as to relationships). Triconodontidae have long been known from the Late Jurassic (US) and earliest Cretaceous (UK). Recently described taxa from the Aptian–Campanian of North America and the Barremian of China add considerably to the diversity of the group, and provide an opportunity to explore the phylogenetic relationships of Triconodontidae in a biogeographic context. We conducted cladistic analyses of dental and mandibular characters in order to test the integrity of, and interrelationships within, the family.

Results provide strong support for monophyly of Triconodontidae. Despite overall similarity of Morrison-Purbeck taxa, relationships of basal triconodontids (Triconodon, Trioracodon, Priacodon) are poorly resolved; similarly, the position of Asiatic Jeholodens (sometimes regarded as sister taxon to Triconodontidae) is unstable. Within the family, North American Cretaceous taxa form a monophyletic (and endemic) clade, Alticonodontinae, which persisted into the Campanian. That radiation was paralleled in Asia by an approximately coeval diversification of Gobiconodontidae.