ACKNOWLEDGMENTS

For loans and permission to apply the methods detailed in this paper to specimens in their care I thank H. A. Nakrem and F.J. Lindemann (both of the Paleontologisk Museum, Oslo), M. Williams and M. Howe (British Geological Survey), B. Paton and M. Taylor (National Museums of Scotland). I thank J. Grant (Ambersil Silicones) and L. Cornish (NHM) for technical advice. The manuscript benefited from the constructive comments of two anonymous reviewers (one of whom pointed out the advantages of storing cured silicon rubber moulds/casts away from ozone and UV light) and the editorial attention of W. Hagadorn and J. Rumford. Prepared while in receipt of a NERC Advanced Research Fellowship (GT5/98/4/ES and NER/J/S/2002/00673).