Towards a better knowledge of the molar morphology and ecology of extant and fossil grass rats (Muridae: Arvicanthis Lesson, 1842)

Abstract African rodents of the genus Arvicanthis are presently restricted to sub-Saharan savannas and to the Nile Valley. In contrast, their distribution during the Quaternary included most of northern Africa, leading to the emergence of local fossil species. To date, there have been no comprehensive studies of Arvicanthis populations in northern Africa, neither to clarify their taxonomy nor their paleoecology. The present study aims to explore both morphology and diet of modern and fossil Arvicanthis species using geometric morphometric and dental microwear analyses on first upper molars. The geometric morphometric analysis efficiently discriminates the studied extant and fossil Arvicanthis species and allowed for the identification of probable geographical variations within the A. niloticus group. Although all extant species of the genus Arvicanthis are predominantly grass-eaters, microwear analyses also highlighted diet differences in various modern populations of A. niloticus, as well as paleodiet inferences in the A. arambourgi fossil species, but no clear link between molar size or shape and diet can be established. This work helps set the stage for a complete revision of the fossil remains of Arvicanthis from northern African Quaternary deposits, and for a better understanding of the geographical and temporal morphological variability of this genus in Africa.