Fig. 4
From: Pheomelanin pigment remnants mapped in fossils of an extinct mammal
Zinc X-ray absorption spectroscopy for fossils and standards. a Zinc K-edge XANES spectra for the fossil and extant mouse specimens, human hair, Zn-bonded eumelanin, Zn–acetate heptahydrate, and ZnS. The two vertical lines indicate the absorption spectrum maxima for pure first shell Zn–S and pure first shell Zn–O species. b First-derivative analysis in the vicinity of the sulfur “white line” region. The ZnS spectrum is displaced to the low-energy side and the Zn–O spectrum from Zn-substituted eumelanin is displaced toward high energy, with the two pheomelanin bearing hair standards intermediate between the two. c Fourier-transformed EXAFS showing relative positions of backscatterers around the Zn central absorber. The heavy dashed line indicates the Zn–S shell. All labels on the vertical lines refer to element shells given in Table 1. Note that the distance values in this figure are not phase shifted and hence are smaller than those presented in the table, but relative positions remain the same. d The two Zn coordination environments resolved in both the extant hair and fur and in the fossil mouse fur. The high abundance of organosulfur-bonded Zn in the fur and skin regions of the A. atavus fossil is most likely due to an originally high concentration of pheomelanin which is enriched in the tetrahedrally coordinated Zn complex shown in the right of the panel. (Zn = dark gray; C = light gray; O = red; S = yellow; N = blue; H = white)
