Abstract

Several remains of fossil phocids (i.e., true seals) have been consistently reported from the Late Miocene and Pliocene strata from the southwestern coast of South America. These fossils, along with those from fossil otariids ( fur seals and sea lions), indicate that a widespread turnover from a phocid- to an otariid-dominated fauna in the Southern Hemisphere transpired during the Late Pliocene or Early Pleistocene. The Neogene fossil record of phocids is primarily dominated by occurrences from southern Peru and northern Chile, with a few isolated findings from central Chile. Until now, no records of fossil seals have been documented from southern Chile, constraining our understanding of the latitudinal variability of the pinniped assemblages and the mechanisms by which their faunal turnover occurred. Here we report the fossil remains of a fossil seal (Monachinae indet.) from the Late Miocene-Pliocene sediments of Guafo Island in the south of Chile. These remains constitute the southernmost occurrence of a fossil seal from the South Pacific Ocean, expanding their geographic range in the southeastern coast of South America more than 1000 km. This finding reveals that phocids inhabited temperate and subantarctic regions in Chilean Patagonia during the late Neogene, suggesting a broader environmental tolerance than previously recognized.