Fig. 1 in Growing up Tyrannosaurus rex: Osteohistology refutes the pygmy "Nanotyrannus" and supports ontogenetic niche partitioning in juvenile Tyrannosaurus

Fig. 1. Femur histology of tyrannosaurid specimens BMRP 2002.4.1 and BMRP 2006.4.4. (A) Mid-cortex of the transverse thin section of BMRP 2002.4.1. Plane-polarized light (PPL) emphasizes osteocyte lacuna density and variability in shape within the laminae, as well as longitudinal primary osteons. In CPL, there is a weak preferred fiber arrangement parallel to the transverse plane of section reflected by regional birefringence. Many primary osteons (POs) have uniformly isotropic fibers with rounded osteocyte lacunae. (B) Mid-cortex of the transverse thin section of BMRP 2006.4.4. Osteocyte lacuna density and variability in shape within the laminae are evident in PPL. CPL reveals varying birefringence associated with bone fiber orientation, but there is a weak preferred fiber arrangement parallel to the transverse plane of section reflected by regional birefringence. Many POs are composed of uniformly isotropic fibers with rounded osteocyte lacunae. (C) Longitudinal section of the mid-cortex of BMRP 2006.4.4. Vascular canals appear as near-vertical, thin, dark columns. As in the transverse section, the primary laminae between POs contain variably arranged osteocyte lacunae. In CPL, the laminae are weakly isotropic (I), corresponding to the poorly organized parallel orientation of fibers in the transverse plane. The laterally compressed osteocyte lacunae in POs are embedded within a uniformly birefringent [anisotropic (AN)] matrix in CPL, indicating that the PO lamellae are longitudinally oriented parallel-fibered bone (LP). (D) On the posteromedial side of the transverse section of BMRP 2006.4.4, there is a parallel-fibered annulus located at the periosteal surface (thickness indicated with blue line). Photographed in CPL. (E) In the transverse section on the posterolateral side, the annulus shown in (D) (blue lines) is overlain by highly isotropic woven-fibered laminae.