Taxonomia da conchostracofauna (spinicaudata, crustacea) da formação pastos bons (jurássico superior), Piauí, Brasil

Abstract

The conchostracan fauna of the Pastos Bons Formation (Upper Jurassic), Parnaíba Basin will be presented in this work. The samples were collected in an area called “Afloramento Taboquinha”, known in the literature as “Muzinho”. The fossiliferous levels are located in dark gray, black and greenish shales, fine sediments, from massive to laminate, and are interpreted as lacustrine sedimentation. The upper portion of the Pastos Bons Formation contains desiccation cracks and fault systems, indicating a high energy environment, and the pelite levels are decreasing in thickness towards the top. Conchostracans were collected at different stratigraphic levels. In the laboratory, the specimens were drawn to build a rectangular structure of the contour of the valve, and from the drawings, precise morphometric measurements were obtained. As a result of the analyses, it was possible to group the specimens into 4 distinct groups, two at the level of species, Cyzicus (Lioestheria) florianensis and Macrolimnadiopsis paloi, and two at the level of genus, Pseudoestheria and Asmussia.