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

Fishes, amphibians, birds, marsupials, armadillos, and rodents are described 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 basis of a radiocarbon AMS date of 8.9 yr BP. The assemblage is largely dominated by the caviomorph rodent Ctenomys, with low frequencies of sigmodontines (Eligmodontia, Reithrodon), marmosines, (Lestodelphys), edentates and other vertebrates. Several lines of evidence suggest a multiple taphonomical origin, including owl pellets, water transport and in situ burial. This interpretation plus the presence of some faunistic elements of xeric environments [as the marmosine Lestodelphys halli (Thomas)] and a low specific richness 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 or the bone concentrations of the fish Corydoras, suggests an interdune paleoenvironment with small fresh-water bodies, similar to the general landscape dominating nowadays the sandy "Southern barrier" of southwest Buenos Aires Province. According to the present intertidal location of the studied deposits, the absolute chronology and the inferred paleoenvironment, the former position of the coast line is discussed.