FIGURE 18. Cheiracanthus grandispinus spines histology. 1-5, NMS G.2019.9.7 in A redescription of the three longest-known species of the acanthodian Cheiracanthus from the Middle Devonian of Scotland

FIGURE 18. Cheiracanthus grandispinus spines histology. 1-5, NMS G.2019.9.7 from Achanarras: 1-3, NMS G.2019.9.7.21, thin section of distal end of pectoral spine, with closeups of the structure of the leading edge ridge and boundary between the main spine osteodentine and the areas bounding the trailing edge groove; 4, NMS G.2019.9.7.11, TS pelvic spine; 5, NMS G.2019.9.7.12, TS through both pelvic fin spines. 6, 7, NMS G.2019.9.8 from Jessie Port, median spine,?anal: 6, TS NMS G.2019.9.8.8 at proximal end of exserted part; 7, NMS G.2019.9.8.15, towards mid spine. 8-10, NMS G.2019.9.35.1-7 from Achanarras, pectoral spine: 8, 9, NMS G.2019.9.35.2, midspine; 10, NMS G.2019.9.35.3, more distal. Scale bars equal 0.5 mm in 1, 4-8, 10, 0.1 mm in 2, 3, 9. bc, basal cartilage.