Jean Gaudant was a qualified specialist of fossil Teleosteans of the continental European Cenozoic and he described many freshwater species. On special occasions he devoted himself to paleohistological techniques to improve his paleontological interpretations. He used for example paleohistology to assign more precisely the phylogenetical position of †Thaumaturus and to describe the histological processes of hyperostosis in two acellular bone fishes (a Cyprinodontidae and a Trichiuridae) and in a cellular bone Clupeidae.