gracilis, Hemiodus Günther [A.] 1864:299 [Catalogue of the fishes in the British Museum v. 5; ref. 1974] Rio Cupai [= Rio Cupari], Rio Tapajós basin, Amazon River drainage, Pará State, Brazil. Lectotype: BMNH 1853.3.19.54. Paralectotypes: BMNH 1853.3.19.55 (1). Lectotype selected by Langeani in Reis et al. 2003:98 [ref. 27061]. •Valid as Hemiodopsis gracilis (Günther 1864) -- (Ortega & Vari 1986:10 [ref. 9708], Taphorn 1992:461 [ref. 23654]). •Valid as Hemiodus gracilis Günther 1864 -- (Langeani 1999:721 [ref. 23914], Lasso et al. 2001:97 [ref. 25928], Langeani in Reis et al. 2003:98 [ref. 27061], Langeani & Moreira 2013:1265 [ref. 32535], Sarmiento et al. 2014:186 [ref. 35006], Melo et al. 2016:132 [ref. 34701], DoNascimiento et al. 2017:38 [ref. 35633], Nogueira et al. 2020:[5] [ref. 38050], Silvano et al. 2020:137 [ref. 38133], Meza-Vargas et al. 2021:14 [ref. 39298], Taphorn et al. 2022:24 [ref. 41297] as gracilis group). Current status: Valid as Hemiodus gracilis Günther 1864. Hemiodontidae. Distribution: South America: Negro, Tapajós, Madeira, Solimões, Amazon, and Orinoco River basins (Bolivia, Brazil, Colombia, Peru and Venezuela). Habitat: freshwater.