Tortella densa (Lorentz & Molendo) Crundwell & Nyholm – a rare species with disjunctive Holarctic distribution is found in Russia for the first time in north-western periphery of the Anabar Plateau (Taimyr District, East-Siberian Subarctic), ca. 3500 km from the nearest localities in North Europe and Alaska. This species differs from the closely related T. inclinata (Hedw.) Limpr. by strongly and uniformly twisted leaves, and massive coroniform papillae on thickened outer cell walls in distal leaf lamina. The description and illustrations of Siberian specimen are given, and a comparison with European and American specimens are provided.