1. Department of Biological Sciences, University of Alberta, CW 405 Biological Sciences Bldg., Edmonton, Alberta, T6G 2E9, Canada,
2. Department of Biology, Columbus State University, 4225 University Avenue, Columbus, Georgia 31907-5645, U.S.A.,
3. Canadian Fossil Discovery Centre, 111-B Gilmour Street, Morden, Manitoba R6M 1N9, Canada
4. Royal Tyrrell Museum of Palaeontology, Box 7500, Drumheller, Alberta, T0J 0Y0, Canada;