Correlation of the Kazanian of the Volga–Urals with the Roadian of the global Permian scale

Recent discovery of an ammonoid assemblage in the Kazanian of the Volga–Urals Region enabled the correlation of the Kazanian with the Roadian of the global Permian scale. The composition of the ammonoid assemblage is similar to other assemblages from Arctic Canada, Novaya Zemlya, and the Verkhoyansk Region. The taxonomic diversity of Roadian ammonoids in the Boreal region is discussed, and existing data on their stratigraphic and geographic distributions are analyzed.