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Novel insight into the origin of the growth dynamics of sauropod dinosaurs

Fig 3

Femur histology of Riojasaurus incertus PVL 3669.

(A) General view of the cortical bone. Growth marks (arrowheads) are formed from the inner to the outer region of the compacta. Normal transmitted light. (B) Detail of the primary bone, which is composed of parallel fibered bone (see mass birefringence). Arrowheads indicate a double LAG. Polarized light. (C) Highly vascularized woven fibered bone in the inner cortex. Note the variation of the vascularization pattern from the inner to the outer area. Polarized light with lambda compensator. (D) General view of the inner cortex showing the variation of the vascular canals arrangement (plexiform in the inner region, reticular in the middle and plexiform again in the outer region). Normal transmitted light. (E, F) General (E) and detailed (F) view of the anterior portion of the cortex showing the irregular arrangement of the vascular canals. Normal transmitted (E) and polarized light with a lambda compensator (F). (G) Detail of Sharpey’s fibers. A single LAG accompanied by an annulus is also observed in the figure. (H, I) Detailed view of LAGs (arrowheads) and annuli in the cortical bone viewed under normal transmitted (H) and polarized light (I). Abbreviations: an: annulus; lag: line of arrested growth; pb: plexiform bone; Sf: Sharpey’s fibers; rb: reticular bone; rv: radially oriented vascular canal; rc: resorption cavity.

Fig 3