Fig. 4 in Morphology and histology of dorsal spines of the xenacanthid shark Orthacanthus platypternus from the Lower Permian of Texas, USA: Palaeobiological and palaeoenvironmental implications

Fig. 4. Serial longitudinal sections of dorsal spine of Orthacanthus platypternus (Cope, 1884), Lower Permian, Craddock Bone Bed, Texas, USA; specimen HMNS-T2, where A represents the most proximal section and E is the most distal. Samples C–E include the denticulate region. Photos of the sections (A1–E1), interpretative drawings (A2–E2). Scale bars 1 mm.