A new species of genus Tiwaripotamon Bott, 1970 (Crustacea, Decapoda, Brachyura, Potamidae) from northern Vietnam, with notes on a similar species identified as Tiwaripotamon araneum.

A new species of semiterrestrial freshwater crab is described from limestone hills in northern Vietnam. Tiwaripotamon caeruleum sp. nov. external morphology is most similar to T. edostilus Ng & Yeo, 2001, and T. pluviosum Do, Shih & Huang, 2016. The new species also resembles T. pingguoense Dai & Naiyanetr, 1994, in gonopod structure. However, it can be distinguished from the other species by its live coloration, serrated anterolateral margin with distinct cleft that separate external orbital tooth from epibranchial tooth and the rest of anterolateral margin, distinct median lobe of posterior margin of epistome, third maxilliped flagellum that reaches half of the merus width and male first gonopod structure. In addition, a similar species, identified as Tiwaripotamon araneum, in an unpublished the master's thesis by Nguyen (2017) is also discussed.