The fossil record of terrestrial tortoises in Argentina is patchy. The aim of the
present contribution is to describe a new species of the genus Chelonoidis coming
from the Middle Pleistocene of Buenos Aires province. This new species shows a unique
combination of apomorphic and plesiomorphic characters unnoticed in other South American
taxa. By Pleistocene times, South America was inhabited by diverse giant and small
terrestrial chelonians that became extinct at the Pleistocene/Holocene boundary. This
should have a deep impact on different plant communities, because tortoises probably
constituted important seed dispersors. In this sense, several extant plant species
that show a patchy distribution and deficient germination and dispersal, may have
been negatively affected by the extinction of Pleistocene tortoises.
