Presence of Hippidion at two sites of western Argentina. Diet composition and contributions for the study of the Pleistocene megafauna extinction.

ALEJANDRO GARCÍA; EDUARDO MARTINEZ CARRETERO

QUATERNARY INTERNATIONAL

Año: 2008 vol. 180 p. 22 - 29

1040-6182

In the Argentinean-Chilean Central Andes, a Neotropical environment characterized by arid to semiarid conditions (Andean hot and cold deserts), we studied the composition of Hippidion diet, and evaluated possible changes that could relate to their extinction. Microhistological analyses were made on feces of Hippidion found at the sites Los Morrillos (31º 43` S - 68º 42` W, 3000 m asl) and Gruta del Indio (34º 35` S, 68º 22` W, 660 m asl). At Gruta del Indio the diet of Hippidion was based mainly on ligneous species. At Los Morrillos, instead, it was based on herbaceous species. This flexibility in diet composition could be a relative adaptive advantage allowing for a longer permanence of this species in comparison to others recorded in the region (such as Megatherium and Mylodon). Nevertheless, this advantage was not enough to guarantee its survival during the Holocene, which could have been affected by diverse agents, such as growing aridization of the area, increasing competition with other species (mainly Lama guanicoe), and human presence, along with a relatively low population density (as expected from the poor presence of Hippidion at the archaeological and paleontological sites of South America (Alberdi et al., 2001). At Gruta del Indio significant changes in the diet of Hippidion corresponding to different moments of the period 31,000 - 9,000 14C years BP are not evident. So, a forced negative shift of diet (eventually caused by environment changes in the LGM) should be discarded as cause of the regional extinction of Hippidion.