The genus Perissocytheridea Stephenson, 1938 (Crustacea: Ostracoda) and evidence of brackish water facies along the Oligo Miocene, Pirabas Formation, eastern Amazonia, Brazil
Abstract Perissocytheridea Stephenson is characteristic of brackish water facies. In 57 samples from the Upper Oligocene to Lower Miocene, from five localities, Pirabas Formation, Para State, Brazil eleven species have been identified. Among these species, four are new reports: Perissocytheridea punctoreticulata n. sp. Perissocytheridea largulateralis n. sp. Perissocytheridea colini n. sp. and Perissocytheridea pirabensis n. sp. five species in open nomenclature: Perissocytheridea sp. 1, P. sp. 2, P. sp. 3, P sp. 4, and P. sp. 5 and two species left in "aff." abbreviation: Perissocytheridea aff. Perissocytheridea pumila and Perissocytheridea aff. Perissocytheridea brachyforma subsp. excavata The distributional pattern of the Perissocytheridea combined with the occurrence of foraminifera Elphidium and Ammonia in the studied sections supports the presence of the brackish water facies to the respective layers. Their quantitative variation through the studied sections indicate more than one phase of salinity reduction (about >5 and