EXCEPTIONALLY WELL-PRESERVED MAMMAL FOSSILS FROM THE UPPER CRETACEOUS (CAMPANIAN) EGG MOUNTAIN LOCALITY (TWO MEDICINE FORMATION)
Recent field work at the Egg Mountain locality, a dinosaur-nesting site in the Upper Cretaceous Two Medicine Formation of Montana, has yielded exceptionally well-preserved and largely autochthonous mammalian fossils. Here, we describe two new specimen blocks. One contains semi-articulated dental, cranial, and postcranial (distal humerus, radius, ulna, femur, tibia, fibula) remains, likely of a single individual of the multituberculate Cimexomys judithae. The other specimen block contains associated, disarticulated dental, cranial, and postcranial (ulna, hand) remains of at least three individuals of the marsupialiform Alphadon halleyi. Study of these specimens has just begun, but they hold potential to improve our assessment of the ecologies of these taxa, clarify our understanding of their phylogenetic relationships, and establish associations among their dental, cranial, and postcranial elements. Moreover, because Egg Mountain is situated in the Western Interior of North America among several intensely studied, often well-dated Late Cretaceous localities with large fossil sample sizes of isolated remains, these specimens will inform studies of these other sites.