Hydroporus sejilashan sp. n., a new diving beetle of the acutangulus-complex from Xizang, China (Qinghai-Tibet Plateau), and notes on other taxa of the genus (Coleoptera, Dytiscidae, Hydroporinae)

Hydroporus sejilashan sp. n. is described from Xizang Autonomous Region (Qinghai-Tibet Plateau), China. It belongs to the acutangulus-complex of the Hydroporus planus-group and can be separated from all four other members of the species complex by the completely distinctly matt surface in both sexes. In addition it can be distinguished from Hydroporus acutangulus Thomson, 1856 and H. polaris Fall, 1923 by the shape of the anterior protarsal claw, which is strongly curved near the base and more straight distally in the latter two species, but evenly curved in the new species and in the other two species of the complex, namely H. tibetanus Zaitzev, 1953 and H. tuvaensis Pederzani, 2001. The habitus of all five members of the complex are provided, along with illustrations of the male and female genitalia of the new species and those of H. tibetanus. The lectotype of H. sumakovi Poppius, 1912, a taxon which until now has been treated as a junior synonym of H. acutangulus, is designated. Preliminary studies reveal that H. sumakovi is probably more closely related to H. polaris than to H. acutangulus. Older, doubtful previous records of Hydroporus nigellus Mannerheim, 1853 from China are confirmed with new records from Qinghai and Sichuan Provinces. Twelve species of the genus Hydroporus Clairville, 1806 are now known from China, only two of which occur in Tibet.