Fig. 3 in Bone microstructure of the sphenodont rhynchocephalian Priosphenodon avelasi and its paleobiological implications

Fig. 3. Postcranial histology of the sphenodont rhynchocephalian Priosphenodon avelasi Apesteguía, 2008 (MPCA-Pv 308) from the Upper Cretaceous Candeleros Formation, Argentina. Black arrowheads signal the position of LAGs. A. Bone histology of the humeri. A1, A2, complete cross sections; A3–A5, detailed views of the cortex showing predominance of poorly vascularized parallel fibered bone and distribution of LAGs; A4, detail of the cortex showing primary vascular canals and LAGs; A5, regions of the cortex marked with double arrows where the tissue presents a better organization and LAGs. B. Bone histology of the radius. B1, general view; B2, B3, details. Note the absence of vascular canals and the mass birefringence of the primary bone tissue. C. General view of the ulna. C1, general view; C2, C3, detailed views showing abundant Sharpey's fibers (C2) and distribution of LAGs (C3). D. Detailed view of the cortex of the fibula showing canaliculi and osteocyte lacunae. E. Detailed view of the cortical bone in the phalange "A" showing abundant Sharpey's fibers. F. General view of the presacral vertebra section. Note the predominance cancellous bone tissue. A1, A2, A4, A5, B1, B3, C, D, normal transmitted light; A3, B2, E, F, cross polarized light with lambda filter. Abbreviations: cn, canaliculi; ic, intertrabecular cavities; ICL, inner circumferential layer; lc, longitudinal canals; nc, nutrient canal; ol, osteocyte lacunae; PFB, parallel fibered bone; rc, radial canals; Sf, Sharpey's fibers.