Body shape :  Massive, rounded in front and laterally compressed behind dorsal fin

Average size :  20 to 35 cm (8 to 14 in)

Coloration :  Yellowish to almost black; flanks with brown marbling in lighter individuals; barbels dark brown to almost black.

External characteristics : Massive head, moderately long, very wide and rounded; small eyes and teeth; 4 pairs of barbels; no scales; dorsal fin towards front of body with sharp spine (serrated or not); adipose fin present; sharp, serrated spine in front of each pectoral fin; very long anal fin; square or slightly indented caudal fin.