Taxonomia e Paleoecologia do Gênero Cyprideis (Crustacea-Ostracoda) da Formação Solimões, Sudoeste da Amazônia Ocidental, Brasil

Abstract

The Solimões Formation comprises Tertiary deposits that extend over thousands of square kilometers across western Amazonia, where the study of ostracods began with the pioneering work of Purper (1977). The genus Cyprideis is widely distributed in these deposits where it is very abundant and diverse, whose identified species are endemic and extinct. This genus has great morphological diversity presenting two evolutionary lineages, one smooth and the other ornamented (Whatley et al, 1998).The present study comprises the identification of Cyprideis species and the paleoenvironmental interpretation of the sedimentary deposits of the Solimões Fm in Aquidabã and Morada Nova, Eirunepé, AM, Brazil. This is the first record of ostracods in these localities, extending the area of occurrence of this unit and its associated ostracodauna and helping to refine the paleoenvironmental and biostratigraphic interpretations. The samples were collected from outcrops exposed on the banks of the Juruá River, at Aquidabã and Morada Nova, southwest of Amazonas State; 1kg of each sample (6 from Aquidabã and 7 from Morada Nova) was processed (grinded, sieved and dried at 50°C) using 30g of sieves 0.42, 0.060 and 0.080 mm for sorting; the specimens were separated by species and later photographed under a Scanning Electron Microscope. The type material was separated for cataloging and deposited in the Museu Paraense Emílio Goeldi's microfossil collection. Six genera and 16 species were identified, 11 of them already recorded in other localities further north of the studied area. Among the Cyprideis species, the following were identified Cyprideis pebasae, C. graciosa, C. longispina, C. lacrimata, C. machadoi and C. olivencai; other 3 species of Cyprideis were identified although kept in open nomenclature. The species Cyprideis pebasae showed great morphological variety where 3 varieties were identified. The association of the ostracod species found allowed us to characterize the deposits as fluvial lacustrine and Middle Miocene.