Supplementary Material_PROCB2 from A fossil protein chimera; difficulties in discriminating dinosaur peptide sequences from modern cross-contamination

A decade ago, reports that organic-rich soft tissue survived from dinosaur fossils were apparently supported by proteomics-derived sequence information of exceptionally well-preserved bone. This initial claim to the sequencing of endogenous collagen peptides from an approximately 68-Myr <i>Tyrannosaurus rex</i> fossil was highly controversial, largely on the grounds of potential contamination from either bacterial biofilms or from laboratory practice. In a subsequent study, collagen peptide sequences from an approximately 78 Myr <i>Brachylophosaurus canadensis</i> fossil were reported which has remained largely unchallenged. However, the endogeneity of these sequences relies heavily on a single peptide sequence, apparently unique to both dinosaurs. Given the potential for cross-contamination from modern bone analysed by the same team, here we extract collagen from bone samples of three individuals of ostrich, <i>Struthio camelus</i>. The resulting LC–MS/MS data were found to match all of the proposed sequences for both the original <i>Tyrannosaurus</i> and <i>Brachylophosaurus</i> studies. Regardless of the true nature of the dinosaur peptides, our finding highlights the difficulty of differentiating such sequences with confidence. Our results not only imply that cross-contamination cannot be ruled out, but that appropriate measures to test for endogeneity should be further evaluated