The genera Anancus, Morrillia, Paratetralophodon, and Tetralophodon, but also the families Choerolophodontidae and Amebelodontidae, were formerly classified as gomphotheres sensu lato. Tetralophodont gompotheres are more closely related to the Elephantidae and amebelodonts and choerolophodonts more primitive than trilophodont gomphotheres. In 2019, a study using collagen sequencing found Notiomastodon to form a clade with the American mastodon, rather than closer to the Elephantidae, as had previously been supposed. The idea that the Mammutidae and Gomphotheriidae are closely related was supported by a morphological study in 2020, which noted the similarity of the molars of the newly resurrected mammutid genus Miomastodon and those of Gomphotherium subtapiroideum/tassyi. However this was contradicted by a 2021 study using Mitochondrial DNA from Notiomastodon, which again found a closer relationship with elephants. Phylogeny of trilophodont gomphotheres according to Mothé et al., 2016: Diet 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. Alternatively, the presence of coarse and hypercoarse scratches along with gouges and large pits suggests the ingestion of foliage and lignified portions. The plant microfossil analysis recovered fragments of conifer tracheid and vessel elements with a ray of parenchyma cells, which corroborates the consumption of woody plants, pollen grains, spores, and fibers. The Aguas de Araxa gomphotheres were generalist feeders and consumed wood elements, leaves, and C3 grasses. Cuvieronius specimens from Chile were exclusively C3 plant eaters, whereas specimens from Bolivia and Ecuador are classified as having a mixed C3 and C4 diet. Notiomastodon showed a wider range of dietary adaptations. Specimens from Quequen Salado in Buenos Aires Province were entirely C3 feeders, whereas the diet of specimens from La Carolina Peninsula in Ecuador was exclusively C4. Possible causes for extinction The results confirm that ancient diets cannot always be interpreted solely from dental morphology or extrapolated from present relatives. The data from Middle and Late Pleistocene periods indicate that over time, a shift occurred in