Although Paleocene mammals have been known from western Canada for nearly 70 years, only during the last 15 years have concerted efforts been made to discover, develop, and describe collections documenting their evolution. Whereas much remains to be done, a faunal succession has been reconstructed, based on collections from 41 mammalian local faunas in Alberta and Saskatchewan, ranging from early Puercan to late Tiffanian age (the first 8 to 10 m.y. of the Tertiary). Latest Cretaceous mammalian local faunas in Saskatchewan show that evolution of progressive “Paleocene aspect” mammals, including condylarths, had begun during the North American Cretaceous as evidenced by the occurrence of fossils in stratigraphie settings free from the complexities that make uncertain the age of faunally similar assemblages in Montana. The Ravenscrag Formation, southwestern Saskatchewan, yields the oldest (early Puercan) Tertiary mammals known from Canada (Rav W-l: MHBT Quarry, Pine Cree Park and Croc Pot localities), including the first discovery of the ancestral primate Purgatorius outside of eastern Montana, and the oldest unarguable carnivoran. Torrejonian mammals are known from the Coalspur Formation (Rocky Mountain Foothills; Diss locality) south of Edson, Alberta. Cochrane 2 (Porcupine Hills Formation, west of Calgary) has yielded unexpectedly diverse earliest Tiffanian mammals, and early Tiffanian mammals have recently been discovered in the Paskapoo Formation near Drumheller (Hand Hills West, lower level), and east of Innisfail, Alberta (Aaron’s Locality). Middle Tiffanian localities occur in the Paskapoo Formation near Red Deer (DW 1 to 3, Mel’s Place, Joffre Bridge Road Cut, Mammal Site No. 1, Erickson’s Landing), and in the Hand Hills (Hand Hills West, upper level); the Police Point local fauna (Ravenscrag Formation), Alberta, appears to be late middle or early late Tiffanian in age. Late Tiffanian mammals at Roche Percée, Saskatchewan (Ravenscrag Formation), and Canyon Ski Lodge, Crestomere School, and Swan Hills, Alberta (Paskapoo Formation) conclude the Paleocene mammalian record known from Canada. Species lists for each locality are presented. The early and middle Tiffanian mammalian record from Alberta fails to show a decline in species numbers seen at several American localities representing this interval: instead of the global cooling sometimes hypothesized to account for this decline, it now seems to be a result of biological or sedimentological events acting on a local scale, sampling error, or some combination of these factors.

Coals in the post-Wapiabi strata of the Rocky Mountain Foothills are found in the upper Campanian (uppermost Belly River and lowermost St. Mary River formations), lower Maastrichtian (upper Brazeau Formation) and lower Paleocene (upper Coalspur Formation) stratigraphic sequences. Large-scale facies relationships within these sequences, combined with sedimentologic data for the coal-bearing strata and their correlatives, indicate that the coal-forming swamps originated in marginal marine, marginal lacustrine, and flood-plain enviornments. The coal-forming swamps developed only when there was a combination of appropriate diastrophic and favorable climatic conditions. This happened twice in the depositional history of the Rocky Mountain Foothills during phases of relative tectonic quiescence (early Maastrichtian and early Paleocene) in the northern, humid part of the basin. At those times the semiarid conditions in the southern part of the basin precluded the formation of coal-forming swamps. The semiarid conditions in this part of the basin were overridden in the late Campanian by the influence of the Bearpaw Sea, which led to the formation of thin coals in the marginal marine environment.