tenuis, Cynodonichthys Meek [S. E.] 1904:101, Fig. 27 [Field Columbian Museum, Zoölogical Series v. 5; ref. 2958] El Hule, Oaxaca, Mexico. Holotype (unique): FMNH 4643. Type catalog: Ibarra & Stewart 1987:30 [ref. 12367]. •Valid as Cynodonichthys tenuis Meek 1904 -- (Costa 2011:242 [ref. 31655]). •Valid as Rivulus tenuis (Meek 1904) -- (Huber 1992:428 [ref. 20639], Espinosa Pérez et al. 1993:38 [ref. 22290], Greenfield & Thomerson 1997:98 [ref. 22947], Murphy & Collier 1997:797 [ref. 25585], Lazara 2001:284 [ref. 25711], Costa in Reis et al. 2003:539 [ref. 27061], Nelson et al. 2004:101 [ref. 27807], Miller 2006:208 [ref. 28615], Costa 2006:139 [ref. 28875] in subgenus Cynodonichthys, Scharpf 2007:11 [ref. 30398], Matamoros et al. 2009:12 [ref. 31241], Page et al. 2013:103 [ref. 32708], Collier 2016:41 [ref. 35018]). •Valid as Cynodonichthys tenuis Meek 1904 -- (Costa 2011:242 [ref. 31655], Lozano-Vilano & De la Maza-Benignos 2016:5 [ref. 35401], Barrientos et al. 2023:274 [ref. 41235], Page et al. 2023:140 [ref. 40505], Quintana 2024:7 [ref. 41186]). Current status: Valid as Cynodonichthys tenuis Meek 1904. Rivulidae: Rivulinae. Distribution: Southern North America, central America: Atlantic Slope river basins (Belize, Guatemala, Honduras and Mexico). Habitat: freshwater.