Fig. 6. A resting (solid outline) and loaded (light-blue overlay) merus segment (m) of the raptorial appendage. Proximal is to the right of the page, dorsal is toward the top of the page. (A) Lateral view of the raptorial appendage. When the extensor muscles contract in preparation for a strike in the load phase, the meral-V (v) rotates proximo-medially (clockwise in this image), which simultaneously causes the bridge (b) to move proximally. When the bridge pushes proximally, it pushes against the saddle (s), which is compressed to form a more concave curve. A mineralized ventral bar (vb) extends proximally from the base of the meral-V. (B) Medial view of the raptorial appendage showing the proximal movement and flexion of the saddle caused by extensor muscle contraction. When seen from the medial view, the saddle is pushed into a notch on the merus. (C) A diagram of the possible areas of elastic energy storage (orange spring icons) during rotation of the merus and flexion of the saddle in preparation for a strike. Here we propose that the meral-V functions as a spring by flexing along its base, similar to a tape spring, to form a tighter curve during extensor muscle contraction. A previous study (Patek et al., 2004) proposed that elastic energy is stored as the saddle compresses into a more concave shape.