Figure 4. Trace evidence for melanin pigmentation in an Eocene fossil feather (USNM 584927).

(a). The dark material towards the distal tip of the feather was examined under a scanning electron microscope. (b–d). Small clusters of elongate, rounded structures within the dark region are morphologically consistent with fossil melanosome casts⁵. Parameters for scanning electron micrographs: (b). 12 kv accelerating voltage, 5.5 spot size, 8.4 mm working distance, 1.4 torr water vapor pressure; (c). 13 kv accelerating voltage, 5.3 spot size, 8.5 mm working distance, 1.4 torr water vapor pressure; (d). 13 kv accelerating voltage, 5.3 spot size, 8.4 mm working distance, 1.4 torr water vapor pressure. Contrast and brightness have been altered for image clarity.