Diodontidae: Porcupine fishes (burrfishes, spiny puffers)

Diagnostic characters: Small to medium-sized fishes to 1 m in length, commonly 20-50 cm. Body wide and capable of great inflation, covered with massive spines which may be quite long; spines with large bases, or roots, under the skin; long spines usually erectile and 2-rooted, short spines fixed in erect position by their 3-rooted bases. Head broad and blunt; gill opening a relatively small, vertical slit immediately before pectoral-fin base; nasal organ usually in small tentacles located in front of large eyes; mouth large, wide and terminal, teeth fused to form a strong, beak-like crushing structure without a median suture dividing the upper and lower jaws into left and right halves. Dorsal and anal fins without spines, set far back on body, and like caudal fin, generally rounded; most fin rays branched; bases of fins often thick and fleshy; no pelvic fins. Lateral line inconspicuous. No normal scales. Colour: background colour light tan to brown, but grey not uncommon; usually overlain with dark brown to black spots, bars and/or blotches; green overtones and yellowish spots may also be present. Undamaged spines covered with skin that continues colour pattern. Belly white, often with yellow overtone. A pelagic species is deep blue dorsally, and pelagic juveniles of other species may also be blue, but pelagic juveniles of some Chilomycterus species are yellow with dark, ring-shaped markings.