Spectroscopic Studies on Organic Matter from Triassic Reptile Bones, Upper Silesia

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 ironoxide-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. Multiple spectroscopic analyses (FTIR, To F-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. 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

The structure and molecular composition of the fossilized blood vessel sections of SUT-MG/F/Tvert/2.

<p>ESEM images and ToF-SIMS fast imaging mode mapping of blood vessels sections displaying their tubular structure. a) ESEM image of thin section showing fossilized blood vessels; analyzed area marked by rectangle. b) the same thin section in optical microscopy; analyzed area marked. c) blood vessel in SEM image, enlarged part of Fig 3a shows location of ToF-SIMS mapping; d‒j) ToF-SIMS ion distribution maps generated for the selected masses corresponding to iron (55.86 Da) and amino acid ions: 30.03 Da–CH₄N⁺ (glycine or proline), 44.05 Da–C₂H₆N⁺ (alanine), 70.07 Da–C₄H₈N⁺ (proline), 86.06 Da–C₄H₈NO⁺ (hydroxyproline), 84.08 Da–C₅H₁₀N⁺ (lysine) and total ion image (Fig 3j) in positive polarity. The distribution of iron (Fig 3d) within the vessel section overlaps with the distribution of ions.</p

ToF-SIMS positive polarity spectra of fossilized blood vessel from demineralized WNoZ/s/7/166.

<p>The spectra show expanded <i>m/z</i> regions associated with amino acids. The chemical structures of the ions (in red, framed) corresponding to a) lysine, b) hydroxylysine, c) proline, d) hydroxyproline, e) glycine, f) alanine, g) leucine, and h) iron are shown in the spectra in panels (a‒h). Other nitrogen-containing organic fragments corresponding to amino acids are also shown.</p

Band assignments of organic signals for different samples (range up to 1800 cm^-1).

<p>Band assignments of organic signals for different samples (range up to 1800 cm^-1).</p