Fig. 5: A polished vertical sections through the fossil skin covered by sediment.

A fossil skin sample (sampling location shown in Fig. 2b) under natural light (a) and UV light (b); dashed lines indicate the approximate position of the polished section in (c). Note that in (b) the fossil skin (bright yellow) is mostly covered by sediment (purple). c–e Scanning electron micrographs of an (uncoated) polished section showing the fossil skin sandwiched between layers of sediment; dashed lines in (e) denote the boundaries among the upper and lower fossil skin layers and the underlying sediment. f Interpretive drawing of (e), showing fossil corneocytes (c) with fractures (f) and isopachous cement (i); stippled fill for the lower skin layer denotes melanosomes. g, h Close-up of the lower skin layer showing mouldic melanosomes. See also Supplementary Figs. 6–8 for variations in melanosome distribution.