nigrescens, Pseudancistrus Eigenmann [C. H.] 1912:234, Fig. 35, Pl. 25 (fig. 2) [Memoirs of the Carnegie Museum v. 5 (no. 1); ref. 1227] Amatuk, Guyana. Holotype: FMNH 53105 [ex CM 1539]. Paratypes: CAS 77343 [ex IU 11960] (1). Type catalog: Henn 1928:85 [ref. 12305], Ibarra & Stewart 1987:70 [ref. 12367], Ferraris 2007:287 [ref. 29155]. Appeared first as name only in Eigenmann 1910:409 [ref. 1224]. •Valid as Pseudancistrus nigrescens Eigenmann 1912 -- (Isbrücker 1980:11 [ref. 2303], Burgess 1989:429 [ref. 12860], Isbrücker 2001:32 [ref. 25653], Isbrücker 2002:27 [ref. 27178], Armbruster 2004:5 [ref. 27844], Ferraris 2007:287 [ref. 29155], De Chambrier & Montoya-Burgos 2008:52 [ref. 29881], Willink et al. 2010:41 [ref. 30670], Silva et al. 2014:2 [ref. 33302], Silva et al. 2015:21 [ref. 33679], Taphorn et al. 2022:53 [ref. 41297]). Current status: Valid as Pseudancistrus nigrescens Eigenmann 1912. Loricariidae: Hypostominae. Distribution: South America: upper Potaro River basin, tributary of middle Essequibo River (Guyana) endemic. Habitat: freshwater.