Estudo taxonômico do gênero Cyprideis, Formação Pebas, região de Iquitos, Peru

Abstract

The Genus Cyprideis belongs to the Cytherideidae Family and recognized for its ecophenotypic plasticity, influenced by several physical-chemical parameters (eg. Salinity, temperature, hydrochemistry, dissolved oxygen content and energy level) that considerably influence its morphological characteristics. In addition, the various adaptive radiation of the genus is recorded mainly in ancient lake systems, for example, on lake Tanganyika, lake Pannon, PaleoMediterraneo, Caribbean and ―lake Pebas" in the Western Amazon. Previous researches were mainly focused on taxonomic studies that contributed to the recognition of a wide variety of taxa; Cyprideis, however the high intraspecific variability of the genus makes it difficult to recognize some species, since the morphological characteristics between then are very similar, which makes it difficult to recognize the actual number of species that currently occur in the Neogene of Western Amazon. Thus, the present work aims the taxonomic study of the Genus Cyprideis of the Pebas Formation, region of Iquitos (Peru), located between the border west of the Marañon basin and the Iquitos arch. The studied samples come from nine outcrops located on the banks of the Amazon River and the Napo River, which provided recognition of eight genera (Cyprideis, Cypria, Penthesilenula, Heterocypris, Macrocypris, Pelocypris, Perissocytheridea and Skopaeocythere) and 22 species of ostracodes. Among these genera, Cyprideis corresponds to 92.5% of the ostracofauna, with 15 species identified, and three are new. Among these are the first record of Cyprideis anterospinosa, Cyprideis marginuspinosa, Cyprideis retrobispinosa and Cyprideis krsticae for the Pebas Formation, previously recorded only in the Solimões Formation. Additionally, the associations identified allowed to infer a predominantly lacustrine environment, which sazonal variations probably influenced in the salinity rate, without evidence of marine influence; besides inferring the age interval between the Middle Miocene and Late Miocene.