Orthosinus medogensis sp. nov. (Coleoptera: Curculionidae: Dryophthorinae) from Xizang, China, with notes on the synonymy of Xerodermus Lacordaire under Orthosinus Motschulsky

Orthosinus medogensis sp. nov., collected in Mêdog County, Xizang Autonomous Region, is described and illustrated. Morphologically, the new species is most similar to O. dudkoi but can be distinguished by the larger body size, shallow transverse sulcus between frons and rostrum, more rugose surface of the rostrum, and parallel-sided form of the pedon. Furthermore, this study addresses the long-standing taxonomic controversy regarding Xerodermus by treating it as a junior synonym of Orthosinus based on the re-examination of published type images, which reveal that the key diagnostic character of ventral eye separation is variable and unreliable at the generic level. Additionally, X. porcellus is recognized as a valid species within Orthosinus.