Leporinus jamesi can be diagnosed from other congeners, except L. apollo, L. affinis, L. amazonicus, L. brunneus, L. cylindriformis, L. desmotes, L. falcipinnis, L. fasciatus, L. geminis, L. macrocephalus, L. muyscorum, L. niceforoi, L. nigrotaeniatus, L. obtusidens, L. pearsoni, L. pitingai, L. trifasciatus, L. unitaeniatus, and L. yophorus, by possessing 42 or more scales on the lateral line (vs. less than 42). It differs from L. desmotes, L. falcipinnis, L. fasciatus, L. pearsoni, and L. yophorus by having dark midlateral blotches on body (vs. body with dark transversal bars), head without dark transversal bars (vs. head with a dark transversal bar between the contralateral orbits), and eight pelvic- branched rays (vs. nine). It can be separated from L. macrocephalus, L. muyscorum, L. obtusidens, and L. trifasciatus by having four teeth on the premaxilla and dentary (vs. three on each). It also differs from L. brunneus, L. cylindriformis, L. geminis, L. niceforoi, L. nigrotaeniatus, L. pitingai, and L. unitaeniatus by having medially dark marks on the pectoral and pelvic fins (vs. hyaline), a body with two dark midlateral blotches, the first one relatively large and conspicuous, and the second small and sometimes inconspicuous, and lacking or inconspicuous presence of a third blotch on the caudal peduncle (vs. three dark mid-lateral blotches in L. cylindriformis, L. geminis, L. niceforoi; a single midlateral stripe that is sometimes fragmented or inconspicuous in L. brunneus; body with a single incomplete mid-lateral stripe running from the vertical through the dorsal-fin origin to the caudal peduncle in L. nigrotaeniatus; approximately six transversally elongate midlateral blotches in L. pitingai; or a single midlateral stripe in L. unitaeniatus) . It is distinguished from L. amazonicus by having more than one dark midlateral blotch (vs. a single dark midlateral blotch posterior to opercle), 42 to 45 lateral line scales ( vs. 45 to 47); and three large transversal dark bars in front of the dorsal-fin origin in specimens measuring approximately 6 cm SL (vs. five or seven thin transversal bars) (Ref. 96869).

Description: Dorsal-fin rays i-ii,9; anal-fin rays ii,7; pectoral-fin rays i,15; pelvic-fin rays i,8;

anal-fin rays ii,7; five series of scales between lateral line and pelvic-fin origin (Ref. 96869).