Figure 1.
Representative SEM micrographs from the distal (red), middle (green), and proximal (blue) portions of a ∼55 myr fossil bird feather from the Danish Fur Formation.
In the micrographs, rod-shaped structures are melanosomes; the concentration of these melanin-containing organelles decreases from the distal to the proximal end of the feather (see Fig. 2). For the fossil, scale bar represents 5 mm. In the SEM micrographs, scale bars represent 2 µm.
Table 1.
Clade-specific frequency of melanin concentration gradients in feathers.
Figure 2.
Correlations between melanosome gradients and feather darkness.
A–B) Melanosome concentrations in darker and lighter sections of fossil (a, top of b) and extant (bottom of b) feathers. C) False color images of copper (left) and zinc (right) concentrations in the fossil feather.