Perissocytheridea carrenoae sp. nov. (Crustacea, Ostracoda) and associated calcareous microfauna from Yecua Formation (Miocene), Bolivia

Abstract

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.