The use of Micro X-Ray Fluorescence for Dinosaur and other Vertebrate Paleontological Studies

Micro-X-ray fluorescence (μXRF) spectrometry is a non-destructive method, which allows rapid identification and mapping of elemental distributions in a wide variety of samples. The recent acquisition of a Bruker Tornado M4 μXRF spectrometer allowed characterization of element distributions in dinosaur bone and eggshell specimens from different localities. Most notably, we used μXRF to investigate the oldest known terrestrial vertebrate eggshells, belonging to Early Jurassic sauropodomorph dinosaurs from South Africa, Argentina and China. With μXRF scans, we were able to identify small fragments of thin eggshell, which would otherwise be difficult to document with classical microscopy or scanning electron microscopy methods. The calcium of the calcareous eggshell and phosphorus of remnants of the membrane are clearly distinguishable from the surrounding matrix. Raman spectroscopic analysis confirmed the respective calcitic and phosphatic nature of the calcareous and membranous layers. In fossil dinosaur bone, calcium and phosphorus are generally dominant elements in the bone tissues, but vascular spaces and other cavities function as a sponge for diagenetic elements such as iron, strontium, yttrium but also uranium and other Rare Earth Elements (REE). Consequently, REE and other trace elements can be a powerful tool for taphonomic investigations. Moreover, the unique patterns of REE, and other trace element concentrations of fossils and fossil sites, also open the potential for application of μXRF to provide a chemical fingerprint of fossil localities. Such fingerprints may ultimately be used to target illegal fossil trade and potentially help resolve legal issues surrounding fossils with questionable provenance. Nonetheless, proper comparative standards need to be established using classical acid solution and/or other mass spectrometry methods, before an extensive database of fossil locality trace element fingerprints can be compiled.