Historians of science have repeatedly, and justly, pointed to the discrepancy between theory and practice in the writings of Cuvier. This discrepancy is especially conspicious in his palaeontological works. No satisfactory analysis of the relation between theory and practice in Cuvier's palaeontology has appeared as yet. In this paper I shall point out the shortcomings of the interpretations of E. S. Russell, H. Daudin, W. Coleman, M. J. S. Rudwick and B. Balan. These authors either overrated or underestimated the role (...) Cuvier's anatomical rules played in his research. Next I shall argue that theory, as embodied in the anatomical rules, played an important role in Cuvier's study of fossil animals. However, the rules were not used as abstract principles of reconstruction. It is a persistent misconception that Cuvier's main concern in the Recherches sur les ossemens fossiles was the reconstruction of extinct animals. Most memoirs deal only with the identification, description and classification of fossil remains. It was mainly on this level that Cuvier—successfully—applied the anatomical rules. As an example of the use he made of the rules, Cuvier's study of the fossil mosasaur from Masstricht will be discussed. This example will also provide a clue to an alternative explanation of the discrepancy between theory and practice in the Recherches. I shall argue that Cuvier's theoretical claims must in part be qualified as examples of his great talent for image-building. (shrink)