From oral pathology to feeding ecology: The first dental calculus paleodiet study of a South American native megamammal

Macrauchenia patachonica Owen, 1838 is a native and extinct Quaternary megamammal from South America. Although studies on macraucheniids started two centuries ago, when Charles Darwin found their first fossils, M. patachonica paleobiology is still poorly understood. Dental calculus is an oral pathology that fossilizes and the analysis of its contents is a useful, simple, and low-cost method to access paleobiological information of fossil mammals. Here, the paleodiet of an adult M. patachonica from Buenos Aires province, Argentina, was assessed using quantitative and qualitative analyses of dental calculus content. The sample was chemically processed and many phytoliths, palynomorphs, sponge spike fragments, and diatom frustules were recovered. Both herbaceous phytoliths (49%) and eudicotyledons (35.4%) were well represented. These results support, for this individual, a mixed feeding habit, including consumption of C₃ and C₄ plants composed of tree/shrub plants and C₃/C₄ grasses, although C₃ could have been more significant. Dental calculus provided direct evidence of paleodiet elements of an extinct South American native mammal for the first time, and such data might support broader paleoecological, paleoenvironmental, and evolutionary studies.