THE BIOMINERALIZATION OF SAUROPOD DINOSAUR SKIN IMPRESSIONS, MORRISON FORMATION, BIGHORN BASIN, WYOMING

The biomineralization of sauropod dinosaur integument impressions offers unique insights into the preservation processes of fossilized trace remnants of skin. Dinosaur skin impressions from the Morrison Formation are rare, and their chemical composition has not been extensively studied. However, skin impressions were abundant in the Two Sisters Quarry #3 near Shell, Wyoming, with some specimens bearing a brown, submillimeter thick mineralized layer. This foundational study employs Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy (SEM-EDS) and X-ray Photoelectron Spectroscopy (XPS) to analyze the elemental distribution and surface chemistry of the integument specimen on a molecular level. This is the first time skin impressions from the Morrison Formation have been studied with these chemical analysis techniques. SEM-EDS allows for high-resolution imaging of the skin’s microstructures, exposing the presence of mineralized components. XPS provides quantitative data on the elemental and chemical states on the surface of the microstructures. We pinpointed and labeled specific locations on the surface of the specimen to test for three categories: keratin, mineralized material, and control matrix. The presence of keratin is supported by trace evidence of nitrogen, sulfur, and carbon due to proteins having disulfide bridges from cysteine residues. The elemental identity of the mineralized material, not previously chemically tested or reported, has been anecdotally referred to as carbonaceous material due to its physical appearance. The mineralized material is confirmed to be elemental carbon, though not carbonate. The control sample, in addition to the expected background elements of aluminum, magnesium, silicon, carbon, and calcium, showed no evidence of sulfur or nitrogen. These findings provide a preliminary framework for future studies on the preservation and biomineralization processes in dinosaur integumentary structures.