Musculoskeletal reconstruction and morphofunctional and palaeoecological analysis of the extinct †Actenomys priscus (Rodentia: Ctenomyidae)

The mammalian skull is a highly malleable structure that reflects both the evolutionary inheritance and particular ecological adaptations. Although rodents exhibit a common set of diagnostic features, their masticatory apparatus presents a great diversity, evidencing its multifunctional role. This variability within extant species allows us to address (palaeo)ecological questions of extinct species, especially those of interest for being basal to specialized groups, such as †Actenomys priscus. Based on fossil materials of †A. priscus, we digitally curated and 3D printed the skull, upon which all jaw adductor muscles were modelled in cold porcelain, anatomical and functional variables related to biting were measured, and bite force was calculated biomechanically. All findings were compared with extant and phylogenetically closed species within a broad spectrum of fossorial behaviours. Although †A. priscus was phylogenetically close to the extant and subterranean-life specialist ctenomyids (tuco-tucos), its skull morphology remained similar to more generalized octodontid species. In particular, although mechanical advantages showed limited ecological differentiation, differences in muscle development aligned more closely with inferred behaviours. Strong similarities in terms of musculature and (estimated) bite force among †A. priscus and the common degus would support the hypothesis of semi-fossorial habit in this extinct species. This study derives from a graduate thesis.