FIG. 14. — Acritolepis urvantsevi n. gen., n in Devonian acanthodians from Severnaya Zemlya Archipelago (Russia)

FIG. 14. — Acritolepis urvantsevi n. gen., n. sp., histological structure of fin spines, Severnaya Zemlya Formation; A, transverse section through the basal part of pectoral spine containing pore openings in the grooves, thin section 3475; B, transverse section through the two-ribbed fragment of pectoral spine (supposedly, middle part), thin section 3481; C, transverse section through the fragment of tuberculated prepectoral spine, thin section 3473; D, longitudinal section through the single-ribbed fragment of pectoral spine, thin section 3472; A, C, D, holotype (LIG 35-A-382). Pod"emnaya River, outcrop 67, bed 12; B, specimen LIG 35-A-402. Matusevich River, outcrop 1, bed 21. Abbreviations: cbo, cellular bone; dt, dentine tubule; lvc, longitudinal vascular canal; md, mesodentine; oc, osteocyte cavity; os, osteon; po, pore opening. Scale bar: 0.1 mm.