rex, Characidium Böhlke [J. E.] 1958:92, Pl. 5 (fig. 7) [Proceedings of the Academy of Natural Sciences of Philadelphia v. 110; ref. 12050] Holotype (unique): ANSP 75949. Type catalog: Böhlke 1984:53 [ref. 13621]. Near the mouth of Río Bobonaza, Chicherota, Province Pastaza, Ecuador. •Valid as Characidium rex Böhlke 1958 -- (Ovchynnyk 1967:33 [ref. 37559]). •Valid as Melanocharacidium rex (Böhlke 1958) -- (Buckup 1993:134 [ref. 20831], Chang & Ortega 1995:3 [ref. 24302], Buckup in Reis et al. 2003:93 [ref. 27061], Barriga Salazar 2014:106 [ref. 35745], Meza-Vargas et al. 2021:20 [ref. 39298]). Current status: Valid as Melanocharacidium rex (Böhlke 1958). Crenuchidae: Characidiinae. Distribution: South America: upper Amazon basin (Ecuador and Peru). Habitat: freshwater.