Early Eocene mammals from the Driftwood Creek beds, Driftwood Canyon Provincial Park, northern British Columbia

ABSTRACT

The early Eocene is an important time in Cenozoic history because it marked the height of global warming, coincident with significant reorganization of the mammalian biota. In North America, our understanding of mammalian diversity during this interval is largely limited to a fossil record south of the 49th Parallel. New discoveries in the early Eocene Driftwood Creek beds (Ootsa Lake Group), northern British Columbia (∼55°N) double the known diversity of Eocene mammals from this Canadian province and provide a window into the mammalian community that lived near the northernmost lake of the Okanagan Highlands, a series of Eocene lake deposits extending north-south from Republic, Washington, to Smithers, northern British Columbia. A diverse insect and fish fauna has been described from Okanagan Highlands Eocene lake shales, together with a diverse flora, interpreted as a cool upland forested landscape. We report the tapiroid cf. Heptodon and an erinaceomorph lipotyphlan Silvacola acares, gen. et sp. nov., from the Driftwood Creek beds. Presence of cf. Heptodon is consistent with the late early Eocene age of the Driftwood Creek beds determined by radiometric dating and palynology. Heptodon is otherwise known from Eocene localities in Wyoming and Colorado as well as Ellesmere Island in the High Arctic, whereas erinaceids are recorded from late Paleocene sites in Alberta, Saskatchewan, and the U.S. Western Interior and are relatively uncommon at Eocene sites in the U.S. Western Interior. Occurrence of cf. Heptodon at Driftwood Canyon supports the hypothesis proposed by others that tapiroids are proxies of densely forested habitats.

ACKNOWLEDGMENTS

We thank T. Ryan (Center for quantitative X-Ray imaging, Pennsylvania State University) for the microCT scan work, and A. Tirabasso (CMN, now at the Royal Canadian Mint) for assembling the specimen in 3D studio max and assistance with preparing Figure 2. Funding for this work in part was from the University of Colorado, the Canadian Museum of Nature, and a Discovery Grant to D.R.G. (DG 311934) from the Natural Sciences and Engineering Research Council of Canada. Collecting at the Driftwood Canyon Provincial Park occurred under a permit from BC Parks to S. B. Archibald (Simon Fraser University). We thank S. MacMillan and J. Howard from BC Parks and F. Tomlin from the Bulkley Valley Museum in Smithers for their assistance and hospitality, and A. Sweet (GSC Calgary) and C. L. Greenwood (Brandon University) for assistance on palynology. We also thank for field work assistance: S. B. Archibald, J. F. Basinger, C. Bataille, G. Bowen, M. Brown, M. Desautels, N. Eberle-Taylor, M. Gilbert, C. Sproat, and D. Wagner. We thank R. Hebda and M. Johns at the Royal British Columbia Museum (Victoria, BC) for curating the Driftwood Canyon mammal specimens. RBCM.EH2012.028.0001.001 was prepared at the University of Colorado by D. Wagner. We especially thank S. B. Archibald and J. Medcraft at Canada Customs for arranging temporary transfer of the perissodactyl specimen to the University of Colorado for study, and S. B. Archibald for his strong commitment to advancing paleontological study of Driftwood Canyon and other BC Eocene fossil sites. The manuscript was improved by the comments of two anonymous reviewers.

Handling editor: Guillermo Rougier