Genus Parvuspotamon Dai & Bo, 1994 Figs 2, 3, 4 Type species. Parvuspotamon yuxiense Dai & Bo, 1994, by original designation. Diagnosis. Medium sized (adult carapace width 16-26 mm, n = 15). Carapace broader than long, ovate; dorsal surface convex, smooth, regions not clear; branchial regions swollen, smooth (Figs 2A, 4A). Epigastric cristae weakly developed, oblique, separated from each other by deep inverted Y-shaped groove; postorbital cristae low, indistinct, confluent with epigastric cristae (Figs 2A, 4A). External orbital angle bluntly triangular, outer margin and anterolateral margin of carapace confluent (Figs 2A, 4A). Anterolateral margin of carapace entire convex, smooth; posterolateral margins of carapace gently converging, smooth (Figs 2A, 4A). Epibranchial tooth indistinct (Figs 2A, 4A). Sub-orbital, sub-hepatic and pterygostomial regions smooth (Figs 2B, C, 4B, C). Antennular fossae slit-like in anterior view; median lobe of epistome posterior margin narrowly triangular (Figs 2B, 4B). Exopod of third maxilliped reaching beyond anterolateral corner of ischium, without flagellum (Fig. 3G). Thoracic sternites 3/4 in male completely fused (Figs 2C, 3C, E, 4C). Vulvae transversely ovate, widely located from each other, touching suture of sternites 5/6 (Fig. 3F). Male pleon broadly triangular (Figs 2C, 3C, 4C). G1 slender, reaching pleonal locking tubercle in situ (Figs 3E, H, I, 4D, E); subterminal segment stout, slightly sinuous (Figs 3H, I, 4D, E); terminal segment slender, relatively long, subconical, strongly sinuous, bent inwards, inner margin strongly concave, ~ 0.6 × length of subterminal segment, without groove for G2 on ventral side, tip rounded, dorsal flap absent (Figs 3H, I, 4D-G). G2 longer than G1; terminal segment relatively long; subterminal segment ~ 1.5 × length of terminal segment (Fig. 3J). Remarks. Parvuspotamon was previously known by two species, P. yuxiense (type species) and P. dixuense. The latter species was recently described by Naruse et al. (2018) based on the characters in the carapace and G1 terminal segment. Based on morphological and molecular data, P. dixuense, however, is transferred to Songpotamon gen. nov. since it possesses the generic characters of the new genus (see Remarks for the new genus). The present revision thus restricts Parvuspotamon only to the type species, i.e., P. yuxiense. The morphological similarities between Parvuspotamon and Songpotamon gen. nov. notwithstanding, Parvuspotamon can easily be distinguished from Songpotamon gen. nov. by the characters in the carapace, vulvae and G1 (see Remarks for Songpotamon gen. nov.). Parvuspotamon is immediately distinguished from most of the remaining Chinese potamid genera by the combination of its medium body size (adult carapace width 16-26 mm), the strongly sinuous G1 terminal segment, and the absence of a flagellum on the exopod of the third maxilliped (Dai and Bo 1994; Dai 1999). Geographic distribution. Parvuspotamon is known only from Yunnan Province of southwest China.

Published as part of Shi, Boyang, Pan, Da & Sun, Hongying, 2023, A taxonomic revision of the freshwater crab genus Parvuspotamon Dai & Bo, 1994 (Decapoda, Brachyura, Potamidae), with descriptions of a new genus and two new species, pp. 13-38 in ZooKeys 1183 on page 13, DOI: 10.3897/zookeys.1183.109948