Figure 1.

Musculoskeletal models of the forelimb across sprawling-parasagittal postures

Musculoskeletal models of the forelimb in the (A) tegu, (B) echidna, and (C) opossum. Left column: models in the global reference pose showing the joint coordinate system used to measure all joint angles. The blue Z-axes are (−) retraction and (+) protraction, the green Y-axes are (−) depression and (+) elevation, and red X-axes are long-axis rotation or (−) pronation and (+) supination. These axes are akin to changes in longitude, latitude, and heading on the joint sphere, respectively. Middle column: anatomically informed neutral poses, found by aligning the humeral head with the glenoid. Rotated joint axes show the movements on the joint sphere from the reference pose to neutral pose. Right column: OpenSim models, in the neutral pose, showing locations of the studied muscles with homologous muscles color coded as detailed in the legend.

See STAR Methods and Figures S1 and S2 for further details on model construction.