Summary
A bioRxiv preprint reports nanoscale chemical mapping of a roughly 150-million-year-old Giraffatitan brancai tooth. The researchers identified magnesium, organic-matter clusters and unexpected Cu3As particles in the enamel, offering clues about tooth formation and fossilisation.
Researchers have mapped the chemistry of a well-preserved dinosaur tooth from the millimetre scale down to the near-atomic scale, finding distinct organic and inorganic structures inside its fossilised enamel. The tooth belonged to Giraffatitan brancai, a sauropod dinosaur that lived roughly 150 million years ago.
The findings appear in a bioRxiv preprint by researchers from institutions including the Max Planck Institute for Sustainable Materials, Ruhr University Bochum, the University of Mainz, CNRS and the University of Rouen Normandy. Because the work is a preprint, its results are presented before formal peer review.
What the chemical map revealed
Dinosaur teeth, like modern mineralised teeth, form through biomineralisation: biological processes that organise mineral crystals into a hard structure. The main mineral discussed in the study is hydroxylapatite, or HAP, which forms nanoscale grains in dental tissue.
The researchers found that magnesium accumulated mainly at the boundaries between HAP grains. These boundaries are the interfaces where neighbouring mineral grains meet. The study also detected fluorine, which the authors associate with diagenesis—the chemical alteration that can occur after an organism is buried and fossilises.
Organic matter appeared both inside the HAP grains and at their boundaries. The authors propose that these organic clusters may have contributed to the tooth’s rapid growth. This is an interpretation of how the chemical pattern may relate to biomineralisation, rather than a direct measurement of growth speed in the fossil tooth.
The analysis also identified unexpected particles with the composition Cu3As across the enamel. Copper and arsenic-containing material was not found in the dentine, the mineralised tissue beneath enamel. The dentine showed empty tubules, microscopic channels normally associated with the tissue’s structure.
Why the enamel–dentine contrast matters
The distribution of elements provides a way to compare substances that may have entered the tooth at different stages. Fluorine is linked in the study to later diagenetic change, while the presence of other elements throughout the enamel—but not in the dentine—is interpreted as evidence that they were incorporated while the tooth was forming.
That distinction is important in fossil chemistry. A fossil tooth contains both traces of its original biological development and chemical changes acquired during burial. Mapping where elements occur, rather than only measuring their overall abundance, can help researchers examine how mineral grains formed and how later alteration affected them.
The authors say the multiscale analysis raises new questions about both biomineralisation and fossilisation. In particular, the location of magnesium, the clusters of organic matter and the Cu3As particles provide features for future comparisons with other teeth and fossil specimens.
The available report describes one Giraffatitan brancai tooth, so the patterns documented here are tied to that specimen. The proposed role of organic clusters in rapid tooth growth also requires interpretation alongside additional specimens and studies of tooth formation. Even so, the work shows how chemical tomography at very small scales can expose structures that are hidden in bulk measurements of fossilised tissue.