Body shape :  deep-bodied, torpedo-like

Average size :  90 to 140 cm (35 to 55 in), 5 to 35 kg (11 to 77 lb)

Coloration :  Gray back and flanks, white abdomen; dark brown or gray fins (no white edging); large black spots on flanks, above pectoral fins, below dorsal fin and on top of snout in younger fish (< 60 cm/24 in).

External characteristics :  Long snout with 4 barbels; ventral, protractile mouth located far behind the eyes; toothless; thick skin lacking true scales but with bony plates on back, flanks and abdomen (plates absent between dorsal and caudal fin); dorsal fin located near caudal fin, above anal fin; heterocercal tail (superior lobe larger than inferior lobe).