NEW AMMONOIDS FROM THE TOURNAISIAN-VISEAN BOUNDARY BEDS ON THE KOZHIM RIVER (SUBPOLAR URAL MOUNTAINS)

Abstract

Six new ammonoid species, Dzhaprakoceras glabrum, D. angustum, D. flexiforme, Neopericyclus polaris, Hammatocyclus incertus, and Helicocyclus aberratus, are described from the Lower Carboniferous Beds on the Kozhim River. Two species, Merocanites applanatus (Frech, 1899) and D. undulatum Riley, 1996, were first discovered in this section. In addition, two new forms assigned to gen. nov. A and gen. nov. B are figured and discussed. Analysis of previously published data on ammonoids and of new findings led to the conclusion that the Tournaisian-Visean boundary in the Kozhim section should be placed 17 m above the base of Member V between the levels of samples 2 and 3, where the genera Michiganites, Kozhimites, and Helicocyclus appear.