Numerous studies have investigated how the skeletal morphology is related to feeding behaviour (Christiansen and Adolfssen 2005; Wroe et al. 2005; Christiansen and Wroe 2007; Ellis et al. 2009; Koyabu and Endo 2009; Koyabu et al. 2009; Koyabu and Endo 2010), although remarkably few studies have focused on the architecture of masticatory muscles from which bite forces are produced. In this regard, the quantification of physiological cross-sectional areas (PCSA) of muscle is critical for estimation of bite forces. PCSA is