1. Department of Ecology and Evolutionary Biology, Brown University, 105 A Biomedical Sciences Building, Providence, Rhode Island 02912, U.S.A.,
2. Department of Pathology and Anatomical Sciences, University of Missouri, 1 Hospital Dr., Columbia, Missouri 65212, U.S.A.,
3. Structure & Motion Lab, Department of Comparative Biomedical Sciences, The Royal Veterinary College, Hawkshead Lane, Hatfield, Hertfordshire AL9 7TA, United Kingdom,