Isotopic paleoecology (δ13C, δ18O) of two megamammals assemblages from the late pleistocene of Brazilian intertropical region

In the late Pleistocene of two localities of Brazilian Intertropical Region (one in Bahia state, and another in Piauí state) lived meso-megamammals herbivores belonging, at least, to three guilds: mixed-feeders (Eremotherium laurillardi, indetermined Equidae, Glyptotherium sp., and Holmesina paulacoutoi), grazers (Notiomastodon platensis, Glyptotherium sp., indetermined Cervidae, and Toxodon platensis) and omnivores (Pachyarmatherium brasiliense). The paleoecologial informations (datings, isotopic diet and niche breadth) were acquired through radiocarbon datings and ratio isotopic analysis of carbon (δ¹³C). The Notiomastodon platensis from Caetanos, Bahia presents a radiocarbon dating of 23,040 ± 55 ¹⁴C years BP (25,604-25,203 Cal years BP) showing that it lived in the region in the late Pleistocene. We propose that Notiomastodon platensis (p_i > 74%) and Glyptotherium sp. (p_i > 76%) had preference for C₄ plants, Equidae preferred to eat C₃ plants (p_i = 62%), while Cervidae and Toxodon platensis were specialists in C₄ plants (p_i = 100%). Eremotherium laurillardi had a genaralist diet, with preference for C₃ plants in Piauí (p_i = 66%), and in C₄ plants in Bahia (p_i = 68%). Holmesina paulacoutoi had a generalist diet, as well, prefering C₄ plants (p_i = 59%). Pachyarmatherium brasiliense was the unique omnivore in this study, and could explore savanna habitats, searching for food.

The δ¹³O values in Caetanos, Bahia ranged from 27.2% to 29.5% and for São Raimundo Nonato, Piauí, from 29.5% to 32.7%. We suggest that the paleoenvironments in both localities was constitude by dry and open environments.