Isotopic analyses of South American gomphotheres suggest a wide diet for "Notiomastodon platensis", except for the fossils unearthed at the localities in Santiago del Estero and La Carolina in Ecuador. Isotope analyses suggested an exclusive C4 diet, whereas every other South American locality indicates an exclusive C3 or mixed C3 and C4 diets. The results also support the latitudinal gradient of C3 and C4 grasses. The stereomicrowear analyses for "N. platensis" exhibited average scratch and pit values, which place it within the extant mixed-feeder morphospace and the higher frequency of fine scratches indicated the ingestion of C3 grasses.