The Yecua Formation (Middle-Late Miocene) is located in the sub-Andean belt in Bolivia, where it is exposed in stream beds and road cuts. The material herein studied came from La Angostura outcrop 60 km from the town of Santa Cruz de La Sierra, just after a short bridge over the Piray River. The calcareous microfossil assemblage comprises five ostracode species: Cypria aff. C. aqualica, Cyprideis spp., Darwinula sp., Ilyocypris? sp. and Perissocytheridea carrenoae sp. nov.; the foraminifer Ammonia beccarii f. tepida; and two unindentified species of the gastropod Heleobia. Although the existence of brackish water and freshwater environments herein identified has been supported by previous authors, it is the first time that a freshwater calcareous microfauna in the Yecua Formation is recorded. Finally, a discussion is presented on the depositional setting and paleogeography of this lithostratigraphical unit.

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-Seventeen species of podocopid and platycopid Ostracoda were recorded in the 26 samples studied from the DSDP (= Deep Sea Drilling Project) Site 515B, Brazil Basin. The Trachyleberididae (eight spp.) and Krithidae (four spp.) are the most-represented families. Most species were left in open nomenclature because of scarcity or poor preservation. The assemblages composition shows moderate similarity to previously-studied deep-sea assemblages. The distribution pattern of the Eocene-Oligocene deep-sea ostracodes is briefl y discussed as a contribution to the understanding of Paleogene ostracode zoogeography.Key words: Ostracoda, Paleogene, paleoceanography, Brazil Basin, deep-sea.RESUMO -Dezessete espécies de ostracodes podocopídeos e platycopídeos foram registradas em 26 amostras estudadas do DSDP (= Deep Sea Drilling Project) Site 515B, Bacia do Brasil. As famílias Trachyleberididae (oito spp.) e Krithidae (quatro spp.) são as mais representativas. A maioria das espécies é registrada em nomenclatura aberta, seja pela escassez de espécimes ou por sua má preservação. A composição das assembleias mostra similaridade moderada quando comparada com outros estudos sobre ostracodes de águas profundas. A distribuição dos ostracodes do intervalo Eoceno-Oligoceno, em águas profundas, é brevemente discutida, visando uma contribuição ao conhecimento da zoogeografi a dos ostracodes paleógenos.Palavras-chave: Ostracoda, Paleógeno, paleoceanografi a, bacia do Brasil, águas profundas.