New mammalian fossils from the Upper Cretaceous Upper Milk River Formation, Alberta, document the occurrence of a possibly new triconodontid species, and of an unnamed therian of metatherian–eutherian grade. The second discovered specimen of the Upper Cretaceous triconodontid Alticonodon lindoei Fox 1969 is described, and Alticondon is classified in a new subfamily. A new genus and species of spalacotheriid symmetrodont represented by lower molars at five positions and apparently not descended from the previously known spalacotheriids Spalacotherium Owen 1854 or Spalacotheroides Patterson 1955 is named and described. A lower molar is referred to the primitive therian of metatherian–eutherian grade Potamotelses aquilensis Fox 1972, The structure, size, and apparent position () of the molar suggest relationship of Potamotelses with the Asiatic Upper Cretaceous Deltatheridiidae and the Lower Cretaceous Aegialodon Kermack, Lees, and Mussett 1965. Kielantherium Dashzeveg 1975 is a junior synonym of Aegialodon.