Extended Data Figure 5 : Humeral midshaft skeletochronology.

From: Life history of the stem tetrapod Acanthostega revealed by synchrotron microtomography

Extended Data Figure 5

All virtual thin sections (voxel size: 0.638 μm) reveal LAGs (black arrows) resulting from the cyclical growth of the cortical deposit (c). They are oriented with the surface of the bone (sb) towards the top and medullary trabeculae (t) downwards. The locations of the thin sections are shown as white dots on the associated 3D models. All 3D models are oriented with their proximal epiphyses6 towards the top. a, Transverse virtual thin section (thickness: 30 μm) showing three LAGs in the cortical bone of the ventral midshaft of the humerus MGUH 29019 (region 7). The inner surface of the cortical bone has been eroded. b, Longitudinal virtual thin section (thickness: 30 μm) showing five LAGs in the cortical bone of the ventral midshaft of MGUH 29020 (region 7). The inner cortical bone is disturbed by a highly vascularised period. LAGs cannot be identified with accuracy in this region. The growth deposits between the LAGs in region 7 are similar in MGUH 29019 and MGUH 29020 (Extended Data Table 1). c, Transverse virtual thin section (thickness: 30 μm) showing two LAGs in the cortical bone of the dorsal midshaft of the specimen MGUH 29019 (region 3). d, Longitudinal virtual thin section (thickness: 50 μm) showing four LAGs in the cortical bone of the dorsal midshaft of UMZC T.1295 (region 3). e, Longitudinal virtual thin section (thickness: 30 μm) showing five LAGs in the cortical bone of the dorsal midshaft of MGUH 29020 (region 3). The growth deposits between the LAGs in region 3 are similar in UMZC T.1295, MGUH 29019 and MGUH 29020 (Extended Data Table 1). Scale bars for virtual thin sections: 0.2 mm. Scale bars for 3D models: 15 mm.