Fig. 7. Mean mouth opening (0–100%) and closing (100–200%) profiles with the calculated four-bar model output for each of the mouth opening mechanism during `type 2' mouth openings (A–C, top), together with length of the protractor hyoidei (m-pr-h; A–C, bottom). Separate graphs are shown for each individual: A (N=5), B (N=8) and C (N=7). Grey bars indicate the time during which the protractor hyoidei shorten. The shaded areas accompanying each curve indicate S.E.M. The broken, green curves give average four-bar model output of mechanism 1C with the protractor hyoidei at minimum length (upper curve) and at maximum length (lower curve) as coupler. Colour codes are indicated in the key above the figure. Mech. 1A,1B,1C, see Fig. 1.