Diagnosis: dorsal profile straight to slightly arched; body dark and dull; rostral lobe poorly developed, its free margin smooth (Ref. 2940, 81282). Distal margin of dorsal fin straight or convex; inner surface of lips with 4-10 transverse folds or costae (Ref. 2940, 28714, 81282). Inferior mouth with well-developed lips forming a sucker-like ring enclosing the jaws; snout typically swollen, as long as or much longer than the postocular part of the head (Ref. 28714). Body not cylindriform, its depth 27-39% of SL (Ref. 28714) or 2.3-3.3 times in SL (Ref. 2940, 81282). Depth of caudal peduncle 0.7-1.3x its length; 26-46 (50-150mm) and 37-47 (150-250mm) gill rakers; scale formula 5.5-7.5/36-40/6.5-7.5; 4.5 scales between lateral line and pelvic-fin base; 16 (18) scales around caudal peduncle (Ref. 2940, 81282). 11-14 dorsal fin branched rays (Ref. 2940, 28714, 81282).

Description: large species; mouth inferior with small posterior barbel at corner of mouth, anterior barbel visible in young, but disappearing with age; distal margin of dorsal fin straight or convex (Ref. 2940, 26190, 81282), some forms with strongly rounded dorsal fin were described as L. pseudocoubie; D:IV,12-15; A:III,5; P:17-19; V:9 (Ref. 2940, 81282). Eyes in superolateral position (Ref. 26190).

Coloration: general appearance dark; back and sides greyish-blue to blackish-maux; belly light; fins blackish or slate-colored; scales on sides bluish-black with mauve or red centre; juveniles grey with scale rows separated by dark, undulate longitudinal lines; a large, round blotch on caudal peduncle (Ref. 2940, 81282).