1. a Division of Natural and Applied Sciences , Northern Virginia Community College , Loudoun Campus, 1000 Harry Flood Byrd Highway, Sterling , Virginia , 20164 , U.S.A. E-mail:
2. b Department of Pathology , Yale University School of Medicine, and Program in Applied Mathematics, Yale University Graduate School of Arts and Sciences , 310 Cedar Street, New Haven , Connecticut , 06510 , U.S.A.
3. c Department of Geology and Geophysics , Yale University , 210 Whitney Avenue, New Haven , Connecticut , 06520 , U.S.A.
4. d Department of Diagnostic Radiology , Yale University School of Medicine , 333 Cedar Street, New Haven , Connecticut , 06519 , U.S.A.
5. e Royal Tyrrell Museum of Palaeontology , Box 7500, Drumheller , Alberta , T0J 0Y0 , Canada