Curculionichthys karipuna is distinguished from all congeners, except C. sabaji and C. paresi, by having an irregular concentration of chromatophores that entirely cover the anal-fin origin and adjacent region, and distal portions of the first unbranched anal-fin ray (vs. absence of such pigmentation pattern). It can be differentiated from C. sabaji by the absence of dark-brown spots scattered over the body (vs. presence); and from C. paresi by the absence of contrasting dark spots at the anterodorsal region of body (vs. presence of such spots). It also differs from C. insperatus, C. sabaji, C. paresi and C. coxipone by having all papillae randomly distributed throughout lower lip (vs. papillae aligned in series that extends from the distal portion of lower lip to dentary). It can be diagnosed from C. insperatus and C. oliveirai by having small, inconspicuous odontodes forming rows on head and trunk (vs. presence of large, conspicuous odontodes); from C. coxipone and C. oliveirai by having a pointed profile of the anterior portion of the head (vs. rounded profile); from C. paresi by having 10-16 premaxillary teeth (vs. 6-10) and 10-14 dentary teeth (vs. 4-7); from C. sagarana by the absence of an unpaired platelet on dorsal portion of caudal peduncle (vs. presence). It can be distinguished from C. coxipone by having 27-28 vertebrae (vs. 29-30) and from C. oliveirai by having 7-8 lateral abdominal plates (vs. 4-5) (Ref. 112322).

Description: Dorsal fin rays ii,7; anal-fin rays i,4; pectoral-fin rays i,6; and pelvic-fin rays i,5 (Ref. 112322).