Distinguished from all species of Leporinus , exceptL. amblyrhynchus , by having

the combination of three teeth on each premaxilla and dentary (tooth formula 3/3) and 12 scale rows around the caudal peduncle (vs. tooth formulae 4/4, 3/4 or 4/3, and 14 or 16 scale rows around the caudal peduncle). Can be diagnosed from Leporinus amblyrhynchus by having three dark blotches on the lateral line (vs. dark longitudinal stripe along the lateral line). Additional characters useful to diagnose Leporinus elongatus include 36 or 37 pored scales on the lateral line, 4 scales rows from the dorsal fin origin to the lateral line and 4 from the lateral line to the base of the pelvic fin (Ref. 93038).