The Adamantina Formation hosts one of the most well-documented Late Cretaceous continental faunas in South America, with crocodyliforms standing out for their unusual richness and ecomorphological diversity. While their taxonomy and anatomy have been widely studied, the understanding of their fossilization processes has been largely overlooked. Here, we apply a multi-technique approach to analyze diagenetic alterations of the skeletal elements of crocodyliforms from the Adamantina Formation, combining information from energy dispersive X-ray fluorescence, scanning electron microscopy with energy dispersive X-ray spectroscopy, micro-Raman spectroscopy, and X-ray diffraction. Our results indicate significant structural and compositional changes, including loss of the organic matrix, void permineralization, ionic substitutions, and recrystallization. Although organic molecules were not unambiguously detected, some Raman spectra exhibited bands in the 1000–1800 cm−1 range that resemble signals previously linked to organic compounds, but which may instead result from fluorescence induced by rare earth elements. Void-filling minerals reflect the prevailing influence of both alkaline (e.g., calcite, relict siderite) and oxidizing (iron oxyhydroxides) pore waters. All samples showed transformation of the original bioapatite into carbonated fluorapatite, highlighting the importance of the precipitation of a more thermodynamically stable phase for the long-term survival of skeletal remains. Raman spectroscopy further revealed differences in fossil apatite preservation among samples, with some showing less alteration and potentially storing original chemical information. The combination of techniques used in this study allowed a comprehensive assessment of the mode and degree of diagenetic alteration of crocodyliform remains, which might be useful when selecting samples for molecular or isotopic studies.
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