Triconodont mammals from the medial Cretaceous of Utah

Abstract

ABSTRACT Herein we describe triconodontid mammals from the upper part of the Cedar Mountain Formation (placed approximately at the Albian–Cenomanian, or Lower–Upper Cretaceous, boundary), Emery County, Utah. Three new species, based on dentulous jaw fragments and isolated teeth, are included; one is referred to Astroconodon, one to Corviconodon (both previously recorded from the Aptian–Albian), and one to a new genus. This diversity is comparable to that seen in the Aptian–Albian Cloverly Formation, and differs from succeeding faunas of the North American Cretaceous, in which triconodontids are rare or lacking altogether. The species differ greatly in size; the largest, at an estimated body weight of 750 g, is the largest known triconodontid and presumably incorporated vertebrate prey into its diet. Triconodont relationships are problematic. Craniodental evidence supports a monophyletic Triconodontidae, and there is weak support for a monophyletic grouping of the North American Cretaceous taxa within the family. However, an exclusive common ancestry for North American Cretaceous triconodontids cannot be readily identified among the morphological diversity known for Late Jurassic taxa. Instead, limited evidence at hand suggests that Late Jurassic Triconodontidae (Triconodon, Priacodon, Trioracodon) form a monophyletic group.