Figure 6

ToF-SIMS spectra from area A1 together with eumelanin and hydroxyapatite.

(a) Negative ion ToF-SIMS spectra from A1 (top) and synthetic eumelanin (bottom). Note that all major peaks in the synthetic eumelanin spectrum are also present in the fossil spectrum and that they occur with approximately the same relative signal intensity distribution (see also Supplementary Table S1), indicating the presence of significant amounts of eumelanin at the surface of the fibrous tissues. Additional peaks in the fossil spectrum originate from phosphate (PO₂⁻ and PO₃⁻ at 63 and 79 u, respectively) and silicate-related ions (SiO₂⁻, SiO₃⁻ and SiO₃H⁻ at 60, 76 and 77 u, respectively). (b) Positive ion ToF-SIMS spectra from A1 (top) and hydroxyapatite (bottom). Note characteristic calcium phosphate peaks at 103, 159 and 175 u in the fossil spectrum, corresponding to CaPO₂⁺, Ca₂PO₃⁺ and Ca₂PO₄⁺, respectively (see Supplementary Table S2 for peak assignments).