Figure 2

SEM of Crato Member BL fish soft-tissues and microfabrics. The images of the analyzed specimens and the localization of micrographs are depicted in Supplementary Figure 3. (a) depicts poorly-preserved muscle fibres, like diagonal ridges, at caudal fin base (Supplementary Figure 3). (b) shows that fibres are composed of Fe oxide/hydroxide (Supplementary Figure 5) sub-spherical to spherical grains with more than 1 µm (and occasionally less than this size, indicated by arrow), locally merged and covered by a “fuzzy” coating. The area highlighted in (b), enlarged in (c), depicts Fe oxide/hydroxide honeycomb-like texture (Supplementary Figure 5). (d), Micrograph showing how muscles are attached to dorsal fin base via tendons and the way these muscles connect to those sub-parallel to column (Supplementary Figure 3). Inset details these observations. Microfabric composition is depicted in Supplementary Figure 5. (e) Micrograph of fish anteroposterior axis (below dorsal fin; Supplementary Figure 3). Images reveal how muscles attach to vertebra, revealing preserved tendons (dashed rectangle), and muscles connected to tendons (big rectangle). Scale bars: (a)– 50 µm; (b)– 10 µm; (c)– 5 µm; (d), (e)– 100 µm.