Average (standard deviation) proximal curvature, distal curvature, and planar orientation values for all disembodied arms (n = 9) while being moved underwater.

The simple bending posture (Fig 4B) consistently had larger proximal curvatures, distal curvatures, and planar orientation differences between proximal and distal segments. Although perfectly planar postures would be expected for observationally straight and simple bending, non-zero values for abduction and internal rotation were measured, indicating that the arm was not in as simple a posture as expected.