ACKNOWLEDGMENTS

The idea for this study was originally hatched in a discussion with K. Carpenter (Denver Museum of Nature and Science), to whom I am also much indebted for showing me, before publication, the original "thagomized" Allosaurus vertebra. H.-J. 'Kirby' Siber and the crew of the SMA organized and invited me to their highly productive Stegosaur Meeting, for where an initial report on this study was given. Their effort and enthusiasm has greatly aided the study of stegosaurs, and I am deeply indebted to them. J.R. Hutchinson and V. Allen (Royal Veterinary College) both greatly aided my understanding of biomechanics, for which I am very grateful, as well as for their comments on a draft of this manuscript. H.-U. Pfretzschner (Eberhard-Karls-University Tübingen) discussed tail swings with me repeatedly, greatly helping my understanding of underlying mechanics of tail motions. Reviews of a previous version of the manuscript by P. Galton (University of Bridgeport) and an anonymous reviewer, and of this version by H. Larsson (Redpath Museum, McGill University) greatly improved the manuscript.