Earliest Divergence of Stagodontid (Mammalia: Marsupialiformes) Feeding Strategies from the Late Cretaceous (Turonian) of North America

Two new unequivocal stagodontids, Fumodelphodon pulveris, gen. et. sp. nov., and Hoodootherium praeceps, gen. et. sp. nov., are described from the Turonian (similar to 92 Ma) Smoky Hollow Member of the Straight Cliffs Formation, of southern Utah, USA. Mammals from this time period are poorly represented; the recovery of these two large stagodontids demonstrates the early emergence of faunal elements mostly associated with the later Cretaceous. These taxa represent the earliest stagodontids with crushing premolars (Fumodelphodon) and sectorial premolars (Hoodootherium), morphologically similar to the well-known stagodontids Didelphodon and Eodelphis, respectively. The similar morphologies suggest that these two new genera may be early members of later Cretaceous stagodontid clades, implying a similar to 7 Ma ghost lineage leading to Eodelphis and a similar to 15 Ma ghost lineage to Didelphodon. A reexamination of stagodontid characters suggests a basal placement of Pariadens within Stagodontidae, contrary to some recent studies. The discovery of two new stagodontids bearing lower molars morphologically similar to, but premolars distinct from, Eodelphis highlights the importance of the specialized premolar morphology for resolving the relationships between genera within Stagodontidae.