nigrensis, Xiphophorus pygmaeus Rosen [D. E.] 1960:100, Figs. 10, 11, 14, 15, 31 [Bulletin of the Florida State Museum, Biological Sciences v. 5 (no. 4); ref. 11945] Nacimiento del Río Choy, San Luis Potosi, Mexico. Holotype: UMMZ 177301. Paratypes: LSUMZ 6264 (1), 6265 & 6388 (6); UMMZ 202825 (now 25). •Synonym of Xiphophorus pygmaeus Hubbs & Gordon 1943, but a valid subspecies as described -- (Rosen & Bailey 1963:65 [ref. 7067]). •Valid as Xiphophorus nigrensis Rosen 1960 -- (Rosen 1979:356 [ref. 22796], Espinosa Pérez et al. 1993:56 [ref. 22290], Rodriguez 1997:674 [ref. 23266], Morris et al. 2001:69 [ref. 25123], Meyer & Schartl 2002:59 [ref. 26066], Lucinda in Reis et al. 2003:574 [ref. 27061], Nelson et al. 2004:106 [ref. 27807], Lucinda & Reis 2005:44 [ref. 29205], Miller 2006:262 [ref. 28615], Scharpf 2007:24 [ref. 30398], Page et al. 2013:111 [ref. 32708], Meyer 2015:403 [ref. 34698], Page et al. 2023:148 [ref. 40505]). Current status: Valid as Xiphophorus nigrensis Rosen 1960. Poeciliidae: Poeciliinae. Distribution: Southern North America: Choy River, Atlantic Slope (Mexico). Habitat: freshwater.