Figure 5
From: The bone microstructure of polar “hypsilophodontid” dinosaurs from Victoria, Australia
Transverse thin section of left tibia from NMV P186047. The tibia microstructure reveals pathologic outgrowth, previously reported to be the result of osteomyelitis. Blue letters reference the magnified regions shown in corresponding panels. Quarter wave plate. (b) The innermost primary cortex varies between fibro-lamellar and poorly organized parallel-fibred with longitudinal primary osteons. The middle to outer cortex is poorly organized parallel-fibred tissue. Vascularity varies from simple primary longitudinal canals, anastomosing canals, longitudinal primary osteons, reticular primary osteons, and radial primary osteons, depending on orientation. Circularly polarized light. (c) Three LAGs (arrows) are visible within the mid-cortex. Plane polarized light. (d) A fourth LAG (arrow) is located very close to the non-pathologic periosteal surface, and in fact blends into it when traced moving from lateral to medial. Plane polarized light. (e) The medullary cavity on the anterior side is filled by woven bone with radial vascularity. Full wave plate. (f) The medullary pathologic tissue joins with the pathologic periosteal surface tissue at the opening between the two sheared halves of the primary bone diaphysis, and the pathologic bone blends with the broken surface of the primary diaphyseal bone. Full wave plate. PC = primary cortex; MP = medullary pathologic bone; PP = periosteal surface pathologic bone. (g) Detail of periosteal pathologic outgrowth. Vascularity is primarily radial, except in narrow bands (arrow) where it becomes more longitudinal. Circularly polarized light. h) Detail of a laterally directed periosteal outgrowth in the tibia of an immature hadrosaurid, Maiasaura (Museum of the Rockies specimen number MOR 005 T-09). This outgrowth is similar in morphology to that observed in the tibia of NMV P186047, consisting of fibro-lamellar tissue with radial vascular canals, interrupted by a “band” of longitudinal fibro-lamellar tissue (arrow). In this image, primary cortex is to the upper right, and the periosteal surface is to the left. Plane polarized light.
