Locomotory habits and palaeoecology of rodents and native ungulates of the Neogene paleocommunities from northwestern Argentina (late Miocene-Pliocene; Santa María Group)

Extinct South American mammals include several herbivorous lineages, most of whose palaeobiology remains poorly understood. The late Neogene deposits of the Santa María Group, northwestern Argentina, have yielded several fossil mammals, including abundant caviomorph rodents and native ungulates. The main goal of this study is to contribute to the understanding of the locomotor diversity and palaeoecology of late Neogene mammal communities from the Santa María Group in Northwestern Argentina. We infer their locomotory habits by analysing postcranial osteological indices and combine these results with available information related to dietary habits and other ecological features. The analysis indicates the presence of large-sized grazers or mixed-feeders with heavy columnar-legged, rhino-like taxa (toxodontids); large- to medium-sized high browsers or mixed-feeders with cursorial gaits (macraucheniids and proterotheriids); medium- to small-sized ambulatory and leaping-cursorial rodent-like forms, capable of digging, that consumed abrasive or hard food items (typotheres); and several medium- to small-sized grazers and mixed-feeders with digging, ambulatory, and leaping-cursorial locomotory habits (caviomorph rodents). Ecological segregation and niche partitioning in the studied paleocommunities appear largely aligned with phylogeny and are mostly consistent with phylogenetic niche conservatism patterns.