Résumé
Hystricomorphy is one of the main cranial morphotypes of rodents and has repeatedly evolved in independent clades, especially in extant Ctenohystrica, Anomaluromorpha, Dipodoidea, and Gliridae. It is characterized by an enlarged infraorbital foramen in which passes the most anterior part of the zygomaticomandibularis muscle. However, due to limited taxonomic and anatomical scope in previous analyses, the extent to which this cranial condition varies as well as its relationship with function and phylogeny remains elusive. To address these questions, we first used traditional dissection and diffusible iodine-based contrast-enhanced computed tomography (diceCT) to describe and compare the anatomy of the masticatory musculature in half the extant generic diversity of hystricomorphous rodents (n = 40 genera). Then, we explored covariation patterns between muscles and cranio-mandibular morphology using geometric morphometrics and linked it to masticatory movements using cineradiography in some key taxa. We show that substantial variations in the anatomy of the masticatory apparatus can be observed at the sub- familial level, which corroborates recent phylogenetic hypotheses. Our observations cast doubts on the previous recognition of convergently evolved hystricomorphous states in distant rodent clades. Additionally, preliminary results based on cineradiographic data dispute simplistic biomecanical views based solely on dental morphology and tooth microwear analyses. These results are promising and highlight the need to incorporate more experimental data to capture the extent and complexity of masticatory biomechanics in rodents.