modestus, Rivulus Costa [W. J. E. M.] 1991:329, Figs. 1 A-B [Revista Brasileira de Biologia v. 51 (no. 2); ref. 20644] Rio Mutum, lower Rio Tapajós basin, Municipio Comodoro, Mato Grosso, Brazil. Holotype: MNRJ 11670. Paratypes: MNRJ 11671 (5). •Valid as Melanorivulus modestus (Costa 1991) -- (Costa 2016:128 [ref. 34900], Nielsen 2017:65 [ref. 35340], Nielsen & Britzke 2019:41 [ref. 36525], Nielsen & Ohara 2024:339 [ref. 41421]). Current status: Valid as Melanorivulus modestus (Costa 1991). Rivulidae: Rivulinae. Distribution: South America: upper Juruena River drainage, Tapajós River basin, Mato Grosso, Brazil. Habitat: freshwater.