Paleoenvironment and paleoecology associated with the early phases of the Great American Biotic Interchange based on stable isotope analysis of fossil mammals and new U–Pb ages from the Pampas of Argentina

Stable isotope analysis evidences dietary changes in toxodontids (Mammalia, Notoungulata) across the Neogene-Quaternary from Argentina

“…3). Such low percentages of C 4 plants in diets might be due in part to the low abundance of this resource at this time; with respect to this, although there is evidence of the presence of C 4 plants in Argentina since 16.5 My ago, they did not become dominant on the South American continent until 7 My ago (Strömberg, 2011) In previous works, the environment of Salinas Grandes de Hidalgo has been identified as an open C 3 grassland, and all the herbivores analyzed present C 3 -based diets (Domingo et al, 2020;Sanz-Pérez et al, 2024) Early Miocene toxodontid Nesodon has been previously considered to be a grazer or mixed feeder (Croft, 2016;Trayler et al, 2020), but morphological and microwear studies indicate that it was probably a browser (e.g., Townsend & Croft, 2008;. Cassini et al (2011) concluded that representatives of this genus were mixed feeders that consumed a combination of resources, possibly based on the availability of vegetation depending on different factors (e.g., seasonality, geographic or environmental conditions, among others).…”

“…Xotodon explored the resources available after the expansion of C 4 plants. Other contributions suggested this shift to C 4 plants in the diet of notoungulates occurred slightly earlier at ~7.6 My (Cerling et al, 1997;Latorre et al, 1997); however, works performed in the Central region of Argentina did not record a significant change in the diets of herbivorous mammals until the earliest Pliocene (Domingo et al, 2020;Sanz-Pérez et al, 2024). This ability to incorporate an increasing variety of dietary resources likely allowed toxodontids to colonize new regions during the GABI, reaching southern North America (MacFadden, 2005;Pérez-Crespo et al, 2020).…”