Evidence for the preservation of collagen within a 195-million-year-old dinosaur bone is presented in a study published in Nature Communications this week. This finding extends the record of protein preservation by over 100 million years from previous studies.
Soft tissues provide a unique source of biological and evolutionary information, but they are rarely preserved during fossilization, and extraction of samples for external examination may compromise the material. Robert Reisz, Yao-Chang Lee and colleagues use a technique called in situ synchrotron-based Fourier transform infrared spectroscopy to examine the chemical contents of a 195 million year old bone of a Lufengosaurus dinosaur without extracting the contents and risking contamination. The analyses reveal preserved protein fragments with the characteristic signals of collagen in the vascular canals of the bone.
Further analyses with Raman spectroscopy also identify hematite particles in the vascular canals. The authors suggest that the hematite was formed by the degradation of hemoglobin and other iron-rich proteins in the blood, and that the filling of the vascular canals with hematite contributed to the preservation of collagen by sealing it inside an inorganic environment. They conclude that this work demonstrates the value of these analytic techniques in providing evidence for the preservation of proteins in fossils.