Late Frasnian Atrypida [Brachiopoda] from the South Urals, South Timan and Kuznetsk Basin [Russia]

Abstract

Late Frasnian AĘpida @rachiopoda) from the South Urals, South Timan and Kuznetsk Basin in Russia (east Laurussian and south Siberian shelf domains in Devonian time) reveal significant genenc and specific diversĘ in the broadly defined Frasnian-Famennian (F-F) bio-crisis time. Eighteen species of aĘpid brachiopods have been recorded, representing 4 subfamilies and 10 genera. The new genus GibberosatrypaMarkovskii & Rzhonsnitskaya, and the new subgenus Spinatrypa (Plicspinatrypa)Rzhonsnitskaya are proposed. Four new species Spinatrypina (Spinatrypina) sosnovkiensis Yudina, Spinar rypa (Plicspinatrypa) rossica Rzhonsnitskaya, Iowatrypa nalivkini Rzhonsnitskaya & Sokiran, and Cartnatina(?) biohermica Yudina are described. The representatives of the Vanatrypinae (including especially conrmon Desquamatia (Desquamatia) alticolifurmis), Spinatrypinae (Spinatrypina) andAtypinae(Pseudoatrypa,?Costatrypa) arewidely distributed in the studied regions. The Pseudogruenewaldtiinae are represented by Iowatrypa artd Pseudogruenewaldtla, of which the first is distributed worldwide, whereas the only undoubted species of the second is resfficted to South Timan, and probably represents a localized latest Frasnian descendant of lowatrypa. The decline phase of aĘpid development was controlled by a variety of environmental factors tied to the globalKellwasser events, although it was not directĘ triggered by anoxic conditions. The investigated atrypid brachiopods, which were all confined to lower latitudes, disappeared dunng the F-F mass extinction, independently of their environmental and biogeographic settings.