Morphology-based taxonomic re-assessment of the Arctic lamprey, (Tilesius, 1811) and taxonomic position of other members of the genus.

The lamprey genus Creaser & Hubbs, 1922 is widespread across Eurasia and North America, but the number and distribution of its constituent species is not firmly established. After a morphological examination of extant type material of the currently recognized species and their synonyms, (Hatta, 1901) is resurrected with Vladykov & Kott, 1978 as its junior synonym. Amongst nonparasitic species (Dybowski, 1869) and are confirmed as present in Japan and the former is also present on Sakhalin. An in-depth study of large samples of nonparasitic lamprey adults from Japan and Sakhalin Island is needed to determine whether the lower trunk myomere (< 66) individuals from these areas represent one or more undescribed species, or , or , or a mixture of these three alternatives. The material from the Anadyr Estuary identified by Berg (1931, 1948) as has been re-identified as and there is no evidence that occurs there. is reported from the Angara River system, Yenisei River drainage, Russia. Vladykov & Kott, 1978 is provisionally considered to be a junior synonym of (Anikin, 1905). Dybowski, 1872, Bean, 1881, Anikin, 1905, Hatta, 1911, and Berg, 1931 are junior synonyms of Tilesius, 1811. A key is provided to adults of the six species recognized as belonging in the genus .