Fig. 5 in New findings reveal that the Middle Triassic ichthyosaur Mixosaurus cornalianus is the oldest amniote with a dorsal fin

Fig. 5. SEM images of microsampled soft tissues of mixosaurid ichthyosaur Mixosaurus cornalianus Bassani, 1886 (BES SC 1000), Sasso Caldo quarry, Besano, Italy, upper Anisian.. A. Collagen fibres packed in parallel bundles from the leading edge of the dorsal fin. B. Close-up of a single fibre showing very fine striations, interpreted as collagen fibrils. C. A pair of collagen fibres from the base of the caudal fin, still covered by a patch of multi-layered scaleless skin. D. Close-up of the skin layers seen in C. Asterisks indicate locations of the back-scattered electron element microanalysis performed on dorsal fin fibres (E), caudal fin fibres (F), and caudal fin skin (G). The peaks illustrate the relative abundance of each element, with higher intensities indicating greater abundance. Note the enrichment of calcium and phosphorous in the fossilised soft tissue, with some variation in secondary minerals.