Fig. 2 Mandibles of Ursus spelaeus (a, b) and Tremarctos ornatus (c) and showing the position of the masseteric fossa (MF) and the premasseteric fossa (PMF). Positions of the landmarks on a mandible of Ursus spelaeus on the lingual side (a) and the labial side (b). The landmarks are described in Table 3. Not to scale. Part A of the figure also displays the biomechanics. The resistance (Fout) at the carnassial of the lower jaw depends on the muscular input force (Fin), the angle of insertion of the muscle onto the jaw (α) and the ratio of in-lever arm or moment arm (Li) to out-lever arm (Lo). Angle of insertion of jaw muscles changes during jaw closing and determines the moment arm of the muscular input force (Mi). Mass pertaining to the masseter, Temp pertaining to the temporalis. Li Mass and Mi Mass happen to be the same in this diagram