One skull to rule them all? Descriptive and comparative anatomy of the masticatory apparatus in five mouse species

Murine rodents display a unique cranial morphology and masticatory musculature. Yet detailed myological descriptions are scarce, especially considering the great diversity of the subfamily and the use of the house mouse and brown rat as model organisms. The masticatory musculature in these two species has been thoroughly described, which allows comparisons with other wild species. Description and comparison of a wide range of species constitutes a necessary step to fully understand how ecological factors may influence the morphology and myology of the skull in the Murinae and vice versa. In this study, we describe the masticatory musculature of five mouse species: Mus caroli, Mus cervicolor, Mus pahari, Mus fragilicauda, and Mus minutoides. For each species, one to five specimens were dissected, and their muscle weights and volumes calculated. One specimen was selected for iodine-enhanced CT-scanning, which allowed us to digitally reconstruct the musculature. We then compared the different masticatory arrangements between these species, as well as with the previous descriptions of the house mouse and brown rat. We show that interspecific differences especially involved the temporalis muscle and zygomatico-mandibularis muscular groups, although some differences were also seen in the pterygoid muscle and masseter muscle groups. We then propose some ecological interpretations for these differences, by interpreting them in terms of functional differences.