Micro-X-ray fluorescence (mu XRF) is an increasingly popular tool within the Earth sciences, although its full potential within palaeontology remains to be explored. In palaeoichthyology, the anatomical descriptions necessary for taxonomic identification of fossil fishes require specialist knowledge and often still relies solely on traditional studies using conventional stereomicroscopy. The quality of preservation, sedimentary matrix, and choice of fossil preparation affects the presence and accessibility of meristic, morphometric and anatomical features used for systematic purposes. Here, we present the first comprehensive study utilising non-destructive benchtop mu XRF-element mapping as a novel scientific tool to expose fossil fish anatomical features, many of which are not commonly accessible. We mu XRF-mapped a total of 66 fish fossils plus a single fossil bird from four different main lithologies from the 55-54 million years old lowermost Eocene Olst and Fur formations; the latter is a world renowned Konservat-Lagerstatte widely known for its exquisitely preserved fossil fauna. Element mapping of Sr, P, Ca, and Ti provided critical and precise information on anatomical characters in both prepared and unprepared fossils that are directly relevant for future taxonomic, phylogenetic and palaeoecological studies, as well as detailed and precise images of squamation patterns and skeletal anatomy hidden by overlying structures or thin layers of sediment. Moreover, preliminary benchtop mu XRF-scans of eight additional specimens show that the method can be successfully applied with similar results in fossil fishes from other and younger deposits, such as the well-known Eocene Pesciara di Bolca (Italy), Green River Formation (United States), and the Oligocene Hochberg Formation (France).. Element-mapping, Fur Formation, carbonate concretion, diatomite, Olst Formation, Teleostei, Eocene, Denmark