Figure 7.

Dot density histogram of relative sarcomere lengths (measured sarcomere length divided by a standard sarcomere length of 2.41 μm; reported as % of optimal length, L₀) for macaque anterior and posterior superficial masseter and anterior and posterior temporalis muscles. Light grey dots represent relative L_s Min (at occlusion) and dark grey dots represent relative L_s Max (at maximum jaw gape), for each muscle region, averaged by species. The average range is 87–143% L₀ for macaque masseter and 88–130% L₀ for the temporalis (solid black brackets). The range for relative sarcomere lengths for these macaque jaw-adductors includes a large portion of the descending limb of the L-T curve, and is both wider and shifted to the right of the L-T curve in comparison with the range reported for jaw and limb muscles (81–107%; dotted black bracket) across a variety of vertebrates (Burkholder & Lieber, 2001). The macaque pattern may be characteristic of facially prognathic primates and other mammals that generate relatively wide maximum jaw gapes.