Radiolarians of Family Heliodiscidae Haeckel, 1981 in the Upper Cretaceous (Campanian–Maastrichtian) Siliceous Deposits of the Vaamychgyn Unit of the Koryak Upland

Abstract

The radiolarians from the Campanian–Maastrichtian deposits of the Vaamychgyn unit sequence (Yakenmyveem River, Koryak Upland, Ekonai terrane) were studied for the first time. On the basis of the joint occurrence of Excentrosphaerella vivenkensis (Lipman), Lithomespilus mendosa (Krasheninnikov), and Stichomitra livermorensis Campbell et Clark, the studied complex is attributed to the Campanian–Maastrichtian. The assemblage contains abundant representatives of the family Heliodiscidae Haeckel, which are widely common in the Boreal and Austral realms and can be of high importance for the stratigraphic and paleobiogeographic paleoreconstructions. The new data allow one to establish the time of the first occurrence of Excentrosphaerella teuria (Hollis), which was previously known only from the Early Paleocene. The species Cromyosphaera vivenkensis Lipman is attributed in this work to the genus Excentrosphaerella Dumitrica.