Nonmarine ostracodes at the Permian–Triassic boundary of the central part of the East European Platform

Extensive geological and paleontological materials from the upper Permian and the Lower Triassic of the East European Platform had been accumulated by the end of the 20th century. Recently obtained new data indicate the stratigraphic continuity of the East European Permian–Triassic succession. The Permian–Triassic boundary is in many sections associated with the boundary between the Zhukovian and Vokhmian regional stages. New stratigraphic data have led to the revision of the temporal distribution of Zhukovian and Vokhmian ostracodes. In contrast to previous ideas, the rapid development of genus Gerdalia already began in the Zhukovian time rather than in the Vokhmian. At the same time, the first Darwinula of the Triassic type also appeared in the Zhukovian. A proportion of the Permian species were found to cross the boundary between Zhukovian and Vokhmian. The degree of similarity between the Permian and Triassic ostracode assemblages turns out to be much higher than previously recognized.