Diagnosis: adipose fin present and fully developed; inner side of pectoral fin spine weakly serrated; barbels well developed, nasal barbel at least reaching to posterior border of eye but never reaching beyond anterior border of opercle; posterior nostrils closer to each other than the anterior nostrils (Ref. 43912, 81643). Medium-sized species, growing over 25 cm SL with distinct marbling, particularly in specimens smaller than 10 cm SL, larger specimens marbled and sometimes with more or less indistinct longitudinal streaks (Ref. 81643). Head massive (Ref. 81643), broad and rectangular (Ref. 43912, 81643). Interorbital width 62-74% HL; mouth width 61-78% HL; 39-52 branched anal fin rays (Ref. 81643). Lower jaw reaching as far as upper jaw (Ref. 81643) or slightly beyond snout (Ref. 43912, 81643).
Description: 39-47 branched anal rays; 43-44 non-fused vertebrae; 9-10 branchiostegal rays on each side of head; caudal peduncle somewhat longer than deep or slightly deeper than long; maxillary barbel reaches at least to halfway between eye and opercle and at maximum to anterior border of opercle; outer mandibular barbel reaches at least to anterior border of opercle and at maximum slightly beyond its posterior border; inner mandibular barbels short, never reaching beyond posterior border of eye (Ref. 43912). A very peculiar species characterized by its massive head and its irregular coloration somewhat resembling the colour pattern of S. marmorarus, from which it is easily distinguished by the presence of an adipose fin (Ref. 43912).
Coloration: (alcohol) preserved specimens: body marbled (particularly in juveniles <10 cm SL); largest individuals marbled and sometimes with lateral bands more or less distinct (Ref. 81643). Head dark brown; sides and dorsum brown with irregularly marbled pattern; dark so-called "tympanum spot" present on each side behind head, where swimbladder lies close below skin; belly and ventral side of head pale and covered with dark, faint speckles; all rayed fins grey-brown except at their bases which are yellowish; a yellowish stripe often along base of caudal fin (Ref. 43912). In life: coloration characterized by its dark irregularly marbled pattern with iridescent metallic blueish and dark greenish reflections (Ref. 43912).