Bite Into This: Preliminary Analysis of Jaw-Adductor Muscle Architecture and Bite Force Measured from DiceCT Images in Tupaia and Strepsirrhine Primates

Abstract

Feeding is a complex behavior involving the synchronization of the mandible, maxilla, muscles of mastication and temporomandibular joint. I quantify the anatomy and three-dimensional architecture of the jaw adductor muscles in a sample of strepsirrhine primates in order to examine how bite force vectors relate to body size, jaw morphometrics, and diet. I hypothesized that species feeding on tough, stiff foods will generate high vertical bite forces on the Phase I Shearing Plane. Additionally, I evaluated (1) the relationship between the vertical component of bite forces to body mass, (2) if muscle fibers were arranged to provide the largest mechanical advantaged in producing a vertical component of bite force, and (3) how tooth wear affects performance estimates. I found that vertical bite forces were higher on the Phase I Crushing Plane. Furthermore, there was a link between body mass and vertical bite force; muscle fibers may be angled to provide a mechanical advantage depending on diet; and tooth wear did seem to influence the occlusal planes, thus affecting performance estimates. The data here provide important in situ estimates for the vertical component of bite force, muscle force, and the vertical component of joint forces which can be compared to and combined with similar studies to determine the best method of muscle analysis and force estimates. Understanding how the jaw adductor system functions we can evaluate and estimate how this system and the environment around it (through diet) has influenced the evolution of the skull.