Biomechanics of the mandible in Canids: the functional consequences of the variability in mandible shape and jaw muscle architecture in dogs and red foxes

The dog is the morphologically most variable species, as a result of its high phenotypic plasticity and the drastic artificial selection that humans have been practicing since the domestication of the wolf. The diversity of morphotypes is particularly well‐illustrated in the head, where the bony reliefs are mainly shaped by the muscles of the masticatory apparatus connecting the skull and the mandible. However, no study to date has explored the functional impact of this variability and high intentional selection. Here, we compare two canid species, one domestic (Canis familiaris) and the other commensal (Vulpes vulpes). For the red fox, anthropogenic selection pressures are unintentional and are more closely linked to a modification of the ecological niche and of the available resources with respect to human activity. Fifty dogs of various breeds and 50 red fox jaws were dissected to study their jaw muscle (temporal, masseter and pterygoid) architecture and to develop a biomechanical model validated by in vivo data. Mandible shape was quantified using geometric morphometrics and the co‐variation between muscle architecture, bite force, and mandible shape is explored using 2BPLS approaches. Applying these approaches to archaeological material will make it possible to follow the morphological and functional evolution of these canids over time, depending on their proximity and the nature of their relationship with humans.