melanostoma, Piabuca Holmberg [E. L.] 1891:192 [Revista Argentina de Historia Natural (Buenos Aires) v. 1; ref. 2192] Formosa (Chaco), Argentina; Ansuncion, Paraguay. No types known. •Valid as Piabucus melanostoma Holmberg 1891 -- (Britski et al. 1999:50 [ref. 24147], Moreira in Reis et al. 2003:173 [ref. 27061] as melanostomus, López et al. 2003:22 [ref. 27366], Menni 2004:78 [ref. 28131] as melanostomus, Mirande 2010:486 [ref. 31006], Barriga Salazar 2014:108 [ref. 35745] as melanostomus, Sarmiento et al. 2014:185 [ref. 35004], Mirande & Koerber 2015:20 [ref. 35117], Koerber et al. 2017:32 [ref. 35267], Meza-Vargas et al. 2021:20 [ref. 39298], Moreira 2024:377 [ref. 40817]). Current status: Valid as Piabucus melanostoma Holmberg 1891. Iguanodectidae. Distribution: South America: Argentina, Ecuador, Bolivia, Paraguay and Peru. Habitat: freshwater.