Arid conditions during the Early Holocene in southwestern Buenos Aires Province (Argentina): Vertebrates and taphonomy.

Fishes, amphibians, birds, marsupials, armadillos, and rodents are describe d from a Holocene site located at Camping Americano, near Monte Hermoso (38 degrees 57' 47" S 61 degrees 22' 48" W, Buenos Aires province, Argentina). The fossil bearing sediments are referred to the Lower Holocene on the bas is of a radiocarbon AMS date of 8.9 yr BP. The assemblage is largely domina ted by the caviomorph rodent Ctenomys, with low frequencies of sigmodontine s (Eligmodontia, Reithrodon), marmosines, (Lestodelphys), edentates and oth er vertebrates. Several lines of evidence suggest a multiple taphonomical o rigin, including owl pellets, water transport and in situ burial. This inte rpretation plus the presence of some faunistic elements of xeric environmen ts [as the marmosine Lestodelphys halli (Thomas)] and a low specific richne ss of sigmodotine rodents indicate that the assemblage were deposited under dryer climatic conditions than the present ones. Additionally, the global faunistic evidence, such as the high frequency of the octodontid Ctenomys o r the bone concentrations of the fish Corydoras, suggests an interdune pale oenvironment with small fresh-water bodies, similar to the general landscap e dominating nowadays the sandy "Southern barrier" of southwest Buenos Aire s Province. According to the present intertidal location of the studied dep osits, the absolute chronology and the inferred paleoenvironment, the forme r position of the coast line is discussed.