During the study of the lichen biota of Yakutia, Acarospora rosulata (Th. Fr.) H. Magn. was identified on the basis of morphological, anatomical, secondary metabolites and molecular data for the first time in Russia. Phylogenetic analysis based on ITS sequences revealed that the studied specimens form a well-supported clade (BS value = 86%) with specimens from Mongolia, USA, and Norway. The studied specimens are characterized by a brown, shiny, squamulose areolate thallus, sometimes with some outer lobes, numerous apothecia immersed in the areoles, a well-developed exciple, simple ellipsoid ascospores (4–5 × 1.5–2.5 μm) and the content of gyrophoric acid as the main substance. Lecanoric and hiascic acids are reported for the first time in the species. A comparative analysis of samples from Yakutia is carried out with descriptions by other authors. Since the original description of the species did not include a holotype, the article also provides a lectotypification based on the original material from Norway. A specimen stored in the herbarium of Uppsala University (UPS) was designated as the lectotype. A comparison with related species is also provided. Keywords: biodiversity, new record, lectotypification, lichens, Russia, Yakutia.