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Distinguished from other species of Bunocephalus by the bony epiphyseal bar very wide (vs. narrow). Differs from its externally most similar species, Bunocephalus doriae, from rio Uruguay and rio Paraná-Paraguay basins, by the following characters: the bony epiphyseal bar very wide (vs. narrow); metapterygoid round, width is equal the height (vs. metapterygoid elongate, width lesser than half of height), well developed lamina in the hypohyal and anterior ceratohyal bones (vs. little developed or absent), 32 vertebrae (vs. 34-35), first procurrent caudal-fin rays well developed (vs. vestigial), vertebral parapophysis 5 distally expanded, shaped like an axe (vs. not expanded) (Ref. 85180).Description: Dorsal-fin rays i,4; anal-fin rays ii,5-ii,7; pelvic-fin rays i,5 (Ref. 85180).