A new species of the family Agnaridae, Lucasioides altaicus sp. nov., is described from the Altai Mountains, southwestern Siberia, based both on morphological characters and molecular data. This species is the first record of Lucasioides from Russia, whose location is the northernmost habitat of terrestrial isopods in indigenous habitats presently known to Eurasia. The diagnostic characters of the new species and a preliminary phylogenetic analysis within Agnaridae are provided.
Keywords: Crustacea, woodlouse, COI, phylogenetic analysis, Altai, Siberia.