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PCA of fossil melanin TOF-SIMS spectra and comparative samples. (A) Principal component plot of TOF-SIMS spectra with the area defined by each sample category (fresh, fossil, matured 200 °C/250 bar, 250 °C/250 bar) indicated with distinct color. (B) Schematic overview of distribution of samples according to inferred/observed color/taxonomy. For loadings, see SI Appendix, Fig. S4.
