Fig. 5. A in Function and evolution of ankylosaur dermal armor

Fig. 5. A spike from the nodosaurid Edmontonia (TMP 1979.147.94) from the Upper Cretaceous Dinosaur Park Formation of Alberta. A. External surface photograph of specimen. B–E. Thin−sections of a spike, dashed lines in A indicate cutting planes. The cortex in the sections surrounds the inner cancellous bone; dark gray: cortical bone consisting of woven or structural fiber bone with many structural fiber bundles; white: cancellous bone. Pipe−like large vascular canals can be seen in the apical and basal part (B, E). Photographs (B1–E1) and interpretive drawings (B2–E2). F, G. Cortical bone tissue of the osteoderm. Detail of the cortex and inner trabecular bone in normal (F) and polarized (G) light; bone surface is to the top. Bone histology of the spike is identical to that of a small osteoderm (DMNH 2452). Structural fiber bundles oriented both perpendicular and parallel to the osteoderm surface occur within the cortex.