Late Miocene capybara in the Atacama Desert reveals a wetter climate and a transcontinental dispersal pathway

We report the oldest record of a capybara (Caviidae: Hydrochoerinae) in Chile, dated at ca. 8.8 Ma, which along with paleobotanical proxy records, indicates a markedly wetter late Miocene Atacama Desert. Today hyperarid, the Atacama contrasts sharply with the semiaquatic ecology of capybaras, which are restricted to perennial wetlands east of the Andes. A partial left M3 (MPC 3000), assigned to Cardiatherium , along with stable isotope data from pedogenic carbonates indicating C 3 -dominated vegetation and phytoliths documenting palms and dicots, provides evidence for persistent freshwater and riparian ecosystems in the southern Atacama during the late Miocene. This occurrence requires ecological connectivity between foreland wetlands and the Pacific margin, implying a transcontinental dispersal pathway. Such connectivity may have been achieved either through a trans-Andean corridor or via a northern route linking the Amazon basin to the Pacific through westward-draining systems. Both scenarios indicate continent-scale hydrologic integration and challenge the long-term persistence of hyperaridity in the region. Instead, they support a substantially wetter late Miocene Atacama, characterized by expanded riparian networks and vegetation capable of sustaining large semiaquatic herbivores.