Wear your diet on your teeth: Dental Microwear Texture Analysis as a proxy for estimating the diet of extinct South American caviomorph rodents

CELINE ROBINET; GILDAS MERCERON; BERNARDINO MAMANI QUISPE; MYRIAM BOIVIN; ADRIANA CANDELA; LAURENT MARIVAUX

Paris

Congreso; 5th International Paleontological Congress (IPC); 2017

Modern caviomorphs or South American hystricognathous rodents exhibit a great taxonomical and ecological diversity,with a broad spectrum of dietary habits, ranging from frugivorous to grass eaters. Their oldest record dates back to the late middle Eocene from Peruvian Amazonia. Continuous paleontological eld eorts have substantially increased the fossil record of early caviomorphs, testifying of a complex early evolutionary history. The late Oligocene locality of Salla (Bolivia) has yielded a diverse assemblage of caviomorphs, including taxa representing the four extant superfamilies. The systematics of the Salla ro-dents is now better established, but little is known regarding their ecology and ecological interactions. Here, we reconstructed the diet of the Salla rodents in performing a Dental Microwear Texture Analysis (DMTA) on the enamel tooth surface. Microwear analyses are proxies providing an insight not on the ability but directly on the use of teeth. The DMTA describes and analyzes automatically surface textures with a high degree of precision. We rstly analyzed the microwear texture of 79 wild specimens of extant caviomorphs showing dierent feeding habits that we compared with those of 241 fossil specimens from Salla. For each specimen of modern and fossil species, we performed a scan on a high resolution silicon mold of the molar occlusal surface with an optical surface prolometer (2). We then applied a scale-sensitive fractal analysis with Toothfrax and Sfrax softwares to describe the microwear textures through four variables: Asfc (complexity), epLsar (anisotropy), HAsfc (heterogeneity of the complexity), and TFV (textural ll volume). Feeding habits among extant caviomorph species provide distinct microwear textural signals for each studied variable. However, diet distinctions for the extinct Salla species arenot as marked as in extant species. Dental microwear textures vary signicantly among Salla species primarily on the complexity and textural ll volume. But only main tendencies regarding the paleoecology and niche partitioning can be advocated for the Salla rodent community. Based on complexity, Incamys, Sallamys, Migraveramus and Cephalomys appear to have been generalist frugivorous (as the modern Dasyprocta), and Eoviscaccia might have fed on tougher items such as leaves (as the modern Phyllomys). In contrast, Protosteiromys and Branisamys seemingly included blander young leaves in their diet (as the modern Coendou).