ACKNOWLEDGEMENTS

This material is based upon work supported by the National Science Foundation under Grant No. EAR-0207194. A zipped copy of the TraceFossil code used to create the material for this paper is available, and the most current version of TraceFossil can be downloaded from the author's site. Please recognize that this program is under active development. Two anonymous reviewers and the editors are thanked for their comments, which greatly improved the manuscript.