More than One Way of Being a Moa: Differences in Leg Bone Robustness Map Divergent Evolutionary Trajectories in Dinornithidae and Emeidae (Dinornithiformes)
(a) Dinornis femur loaded in compression (0° from the longest principal axis) experienced a significant degree of bending due to off-axis application of force on the femoral head. (b) Dinornis tibiotarsus experienced lower values of σvm under compression, and underwent less bending due to application of forces on the intercondylar eminence. (c) Pachyornis tibiotarsus loaded in bending (90° from the longest principal axis). σvm increases towards the fixed end of the beam, with localised areas of stress related to variations in cortical wall thickness. (d) Slice through midshaft of c. Values of σvm are highest at the extreme compressional and tensional cortices with a neutral axis of lowest stress values running between. (e) Slice through midshaft of Pachyornis femur loaded in torsion. Stress values increase radially from the endosteal to periosteal surface, with the highest stresses located in regions where cortical wall thickness is at a minimum. For (d) and (e), bone orientation is indicated by coordinate system (a–p, anteroposterior; m–l, mediolateral).