luetkenii, Tetragonopterus Boulenger [G. A.] 1887:173 [Annals and Magazine of Natural History (Series 5) v. 19 (no. 111) (art. 23); ref. 17020] San Lorenzo, Rio Grande do Sul, Brazil. Syntypes: BMNH 1885.2.3.78-80 (3), 1886.3.15.35-38 (4). •Valid as Hyphessobrycon luetkenii (Boulenger 1887) -- (Malabarba 1989:135 [ref. 14217], Britski et al. 1999:43 [ref. 24147], Lima & Malabarba in Reis et al. 2003:137-138 [ref. 27061], López et al. 2003:27 [ref. 27366], Casciotta et al. 2003:104 [ref. 28130], Menni 2004:77 [ref. 28131] as luetkeni, Almirón et al. 2004:674 [ref. 27987] as luetkeni, Almirón et al. 2006:895 [ref. 29163], Miquelarena & López 2010:6 [ref. 30749] as lüetkenii, Mirande 2010:512 [ref. 31006], Di Dario et al. 2013:262 [ref. 37503], Catelani et al. 2014:931 [ref. 37496], Litz & Koerber 2014:15 [ref. 33622], Mirande & Koerber 2015:26 [ref. 35117], Teixeira et al. 2016:474 [ref. 34088], Bertaco et al. 2016:414 [ref. 34561], Petry et al. 2016:302 [ref. 34966], Nión et al. 2016:30 [ref. 35565], Koerber et al. 2017:41 [ref. 35267]). •Valid as Deuterodon luetkenii (Boulenger 1887) -- (Koerber et al. 2020:3 [ref. 37480], Mirande & Koerber 2020:2 [ref. 37594], Reis et al. 2020:459 [ref. 38364], Terán et al. 2020:7 [ref. 37440], Koerber et al. 2021:3 [ref. 38894], Giora & Wingert 2023:131 [ref. 41026], Koerber et al. 2023:3 [ref. 40355], Loureiro et al. 2023:68 [ref. 40506], Koerber 2024:3 [ref. 41228]). Current status: Valid as Deuterodon luetkenii (Boulenger 1887). Acestrorhamphidae: Stygichthyinae. Distribution: South America: coastal river drainages and Uruguay River basin in Rio Grande do Sul State (Brazil); Paraíba do Sul River in Rio de Janeiro State; Paraguay River basin (Argentina, Brazil, Paraguay and Uruguay). Habitat: freshwater, brackish.