A Primitive Higher Mammal from the Late Cretaceous of Southern Utah

Cretaceous mammals of the southwestern United States are poorly known. Herein, a new genus and species is described from the Wahweap Formation of southern Utah. The Wahweap fauna is of probable Aquilan age, otherwise known by a single local fauna from Alberta, Canada. Although the new species is clearly a “higher” mammal, it bears no known features uniting it with either marsupials or eutherians. The distribution of dental characters among tribosphenic therians suggests common ancestry of marsupials and eutherians from a taxon advanced with respect to “aegialodonts,” in turn indicating that dentally advanced Tribosphenida were more widely distributed than the known record indicates.