Latest Pleistocene paleoecology of Jefferson's ground sloth (Megalonyx jeffersonii) and elk-moose (Cervalces scotti) in northern Illinois

New records of Jefferson's ground sloth (Megalonlyx jeffersonii) and elk-moose (Cervalces scotti) from Lang Farm provide the first precise temporal correlation of these taxa with the specific environments inhabited by them near the time of their extinction. Six AMS C-14 measurements establish an age of 11,405 +/- 50 C-14 yr B.P. for Lang Farm Cervalces and an age of 11,430 +/- 60 or 11,485 +/- 40 C-14 yr B.P. for the Megalonyx. These measurements represent the youngest C-14 dates for these two genera based on direct dating. Comparison of the dates with pollen data from northern Illinois indicates that these species inhabited a nonanalog environment that was transitional from mid-latitude tundra to mixed conifer and deciduous woodland. Although spruce (Picea sp.) was dominant, it was less abundant than prior to 12,500 C-14 yr B.P. The presence of black ash (Fraxinus nigra) and fir (Abies sp.) indicates a wet climate and heavy winter precipitation. This may have been the preferred habitat for Cervalces because of its narrow geographic range. However, this habitat type was only one of many occupied by Megalonlyx as indicated by its broad geographic distribution. (C) 2003 University of Washington. All rights reserved.