How long can old fossils retain soft tissue? Research recently published in the journal PloS ONE documents perhaps the oldest cases of biomolecules supposedly hailing from the Early/Middle Triassic, ca “247.2 million years” ago.
Polish scientists examined the fossils of two ancient reptiles, and found much more than just old-looking stony material:
“Fossil biomolecules from an endogenous source were previously identified in Cretaceous to Pleistocene fossilized bones, the evidence coming from molecular analyses. These findings, however, were called into question and an alternative hypothesis of the invasion of the bone by bacterial biofilm was proposed. Herewith we report a new finding of morphologically preserved blood-vessel-like structures enclosing organic molecules preserved in iron-oxide-mineralized vessel walls from the cortical region of nothosaurid and tanystropheid (aquatic and terrestrial diapsid reptiles) bones. These findings are from the Early/Middle Triassic boundary (Upper Roetian/Lowermost Muschelkalk) strata of Upper Silesia, Poland."
The researchers pointed out that they really found what they reported:
"Multiple spectroscopic analyses (FTIR, ToF-SIMS, and XPS) of the extracted ‘blood vessels’ showed the presence of organic compounds, including fragments of various amino acids such as hydroxyproline and hydroxylysine as well as amides, that may suggest the presence of collagen protein residues.”
Just to keep on the safe side, however, they put blood vessels in quotes.
“Because these amino acids are absent from most proteins other than collagen, we infer that the proteinaceous molecules may originate from endogenous collagen. The preservation of molecular signals of proteins within the ‘blood vessels’ was most likely made possible through the process of early diagenetic iron oxide mineralization. This discovery provides the oldest evidence of in situ preservation of complex organic molecules in vertebrate remains in a marine environment.”
To their credit, they acknowledged finding “complex organic molecules” in the bones.