parnaibensis, Rivulus Costa [W. J. E. M.] 2003:2, Figs. 1-2 [Boletim do Museu Nacional do Rio de Janeiro, Zoologia, Nova Série No. 511; ref. 27635] Lagoon close to the road BR-135, 18 kilometers northeast of São Dimas, about 9°40'S, 45°00'W, Parnaiba River basin, Piauí, northeastern Brazil. Holotype: MCP 29639. Paratypes: MCP 29640 (5); UFRJ 4962 (25), 5449 (4, 2 c&s). •Valid as Rivulus parnaibensis Costa 2003 -- (Costa 2006:162 [ref. 28875] in subgenus Melanorivulus). •Valid as Melanorivulus parnaibensis (Costa 2003) -- (Costa 2011:241 [ref. 31655], Nelsen & Costa 2011:241 [ref. 31655], Ramos et al. 2014:4 [ref. 35321], Nelsen & Pinto 2015:136 [ref. 33903], Costa 2016:139 [ref. 34900], Nielsen 2017:66 [ref. 35340], Nielsen & Britzke 2019:42 [ref. 36525], Koerber et al. 2022:75 [ref. 39235]). Current status: Valid as Melanorivulus parnaibensis (Costa 2003). Rivulidae: Rivulinae. Distribution: South America: Parnaíba River basin (northeastern Brazil). Habitat: freshwater.