1. Center for Functional Anatomy and Evolution, Johns Hopkins University School of Medicine, 1830 E. Monument St., Baltimore, MD, 21205, U.S.A.
2. Department of the Geophysical Sciences, University of Chicago, 5734 S. Ellis Ave., Chicago, IL, 60637, U.S.A.
3. Department of Geosciences, Virginia Tech, 926 W. Campus Dr., Blacksburg, VA, 24061, U.S.A.