2026 Volume 35 Issue 4 Pages 193-200
Type I collagen is a principal target in paleoproteomic studies of fossil bone, but assessing its endogeneity from specific tissues is difficult once extraction removes proteins from their original context. We examined three approximately 35-million-year-old mammalian and reptilian vertebrate fossils from the upper Eocene Ergilin Dzo Formation of Mongolia by combining Van Gieson staining with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). An established bright-field method for observing Van Gieson-stained nondemineralized fossil sections was extended to include fluorescence microscopy. All three fossils showed clear staining within the preserved bone matrix, with broadly corresponding patterns under bright-field and fluorescence microscopy. SDS-PAGE showed the α1, α2, β, and γ components of type I collagen in the modern reference material and all fossil extracts, but not in the corresponding extraction blanks. Together, these results support the preservation of endogenous type I collagen with substantial molecular integrity in all three fossils. The present findings suggest that endogenous type I collagen can persist in and be extracted from approximately 35 Ma fossil bone deposited in a paleoenvironment that was not persistently cold. Combining fluorescence-assisted in situ visualization with molecular analyses may broaden paleoproteomic investigations across deeper time and more diverse preservational environments.
