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 Tyrannosaurus rex 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 Brachylophosaurus canadensis fossil were
reported that have 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, Struthio camelus. The resulting LC–
MS/MS data were found to match all of the proposed sequences for both
the original Tyrannosaurus and Brachylophosaurus 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.