Diagnosis: tooth patches broad (Ref. 34006, 44050). Pectoral fin placed ventrally; 8-12 anal-fin rays; 19 caudal-fin rays (ii-7-8-ii); 43-47 vertebrae (Ref. 44050). Body and head marked with large blotches (Ref. 34006, 44050). Spotting and blotching concentrated posteriad; caudal and anal fins unmarked or lightly spotted; paired fins rarely spotted (Ref. 44050).

Description: body and head distinctly depressed; jaws equal or lower jaw slightly prominent; 19-21 abdominal vertebrae; 22-27 caudal vertebrae (Ref. 44050, 57130). 19 total caudal fin rays (ii-7-8-ii)(Ref. 57130).

Coloration: pigmentation similar to M. electricus, but more finely and sparser spotted, with paired fins rarely spotted; small specimens (<80mm SL) with long saddle of a shade slightly darker than ground color, extending from base of caudal fin to anterior end of adipose fin, with no pale interspace; saddle continues onto adipose fin, which has a pale distal margin; anal and caudal fins in juveniles have dusky bars set off by pale bases, and clear distal margins, and there are scattered spots and blotches (up to several times an eye diameter) on the flank and dorsum, but not on the fins (Ref. 44050). Saddle and bar pigmentation very faint, even in juveniles (Ref. 57130).