Badistemon Yeo & Ng, 2007

Mitra, Santanu, Monica, Thingbaijiam & Waikhom, Mema Devi, 2020, A new species of freshwater crab of the genus Badistemon Yeo & Ng, 2007 (Decapoda: Brachyura: Potamidae: Potamiscinae) from Manipur State, India with the reassignment of Potamiscus pealianus (Wood-mason, 1871), Zootaxa 4838 (4), pp. 475-490 : 476

Genus Badistemon Yeo & Ng, 2007

Type species: B. turgidulum ( Alcock, 1909) (subsequent designation by Yeo & Ng, 2007)

Diagnosis: Carapace size small to medium (maximum cw 21.5 mm to 48.7 mm), relatively squarish, distinctly wider than length, high, longitudinally convex; epigastric cristae rugose, separated from post orbital cristae by a distinct groove, post orbital cristae distinct, confluent with epibranchial tooth; anterolateral margin gently convex, distinctly longer than posterolateral margin; third maxilliped exopod with flagellum, shorter than merus width; dactylus and propodus of ambulatory legs relatively long, slender; thoracic sternite-8 completely separated by longitudinal median line, no median transverse ridge; sternopleonal cavity not exceeding the imaginary line joining posterior edge of cheliped bases; G1 terminal segment relatively long, subcylindrical to subconical with low and short dorsal flap, subterminal segment broad at base, distal end neck-like, suddenly narrowed; G2 slender, terminal segment longer than ca. 0.5 times length of basal segment, basal segment outer margin expanded (modified from Yeo & Ng, 2007).

Remarks. Potamon (Potamon) turgidulum ( Alcock, 1909) , was described by Alcock (1909: 245) based on 11 males and 6 females from Burma (now Myanmar)(ZSI-C6952/3), but didn’t designate a holotype from those specimens. Later, Bott (1970) collected one male (SMF 1761) and two females (MBa, 19a) specimens from Meelan of Myanmar and re-assigned the species as Ranguna (Ranguna) turgidula ( Alcock, 1909) . Ng (1996) clarified that Bott’s (1970) decision about P. (P). turgidulum (as Ranguna ) (1970: pl. 38 fig. 36–37, pl. 51 fig. 53–54) was based on misidentified material. Subsequently Yeo & Ng (2007) re-assigned Alcock’s species as a new monotypic genus, Badistemon , based on their examination of the syntypes in the repository of Zoological Survey of India, Kolkata (ZSI-C6952/3). We examined the syntypes and found only 7 males and 1 female are in well condition and here we take the opportunity to designate a lectotype male (cw 28.7 mm × cl 23.5 mm) for B. turgidulum from these syntypes to stabilize the taxonomy of this species.