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.