1. Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
2. Geosciences Research Division, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093-0244, USA
3. Center for Tropical Paleoecology and Archaeology, Smithsonian Tropical Research Institute, Box 2072, Balboa, Republic of Panama
4. Naturhistorisches Museum Basel, Augustinergasse 2, Basel CH-4001, Switzerland