Curculionichthys itaim is distinguished from all its congeners, with the exception of C. coxipone, C. sabajiand C. tukana by possessing eight to ten plates in abdominal lateral plates series (vs. four to six plates in abdominal lateral plates series); from C. coxipone and C. oliveirai by having the anterior profile of the head pointed (vs. anterior profile of the head rounded); from C. insperatus, C. paresi C. sabaji and C. tukana by having papillae randomly distributed throughout the lower lip (vs. the papillae aligned in series that extends from the distal portion of lower lip to dentary); and from C. insperatus and C. oliveirai by the lack of large conspicuous odontodes forming rows on head and trunk (vs. large, conspicuous odontodes forming rows on the head present). Curculionichthys itaim can be further diagnosed from C. coxipone and C. luteofrenatus by having 22-23 medial plates series on lateral portion of the body following the lateral line (vs. 25-27 medial plates series); from C. sabaji by the lack of dark-brown spots scattered over the body (vs. dark-brown spots on the body present); from C. oliveirai and C. tukana by having two or three irregular median plates series in abdomen (vs. one median plate series in abdomen); from C. karipuna by lacking an irregular concentration of chromatophores that entirely cover the anal-fin origin and adjacent region, and distal portion of the first unbranched anal-fin ray (vs. having such pigmentation pattern); from C. paresi by having 11-18 dentary teeth (vs. 4-7), and the lack of contrasting dark spots at the anterodorsal region of body (vs. such pigmentation pattern at the anterodorsal region of body prsent); from C. piracanjuba by having odontodes forming aligned rows, more evident in the dorsal portion of head and in the lateral portion of caudal peduncle (vs. odontodes not forming rows); and from C. sagarana by the lack of one unpaired platelet on the dorsal portion of the caudal peduncle (vs. present) (Ref. 118146).

Description: Dorsal-fin ii,5; anal-fin i,5; pectoral-fin i,6; pelvic-fin i,5 (Ref. 118146).