They are related to the true porcupines, but have shorter spines, and are arboreal in their habits
Any Old Word rodent of the genus Hystrix, having the back covered with long, sharp, erectile spines or quills, sometimes a foot long
A porcupine is an animal with many long, thin, sharp spikes on its back that stick out as protection when it is attacked. an animal with long, sharp parts growing all over its back and sides (porc espin, from porcus ( PORK) + spina ). Heavy-bodied, solitary, slow-moving, nocturnal rodent with quills (modified hairs) along the back, tail, and, on certain crested species, the neck and shoulders. The quills are easily detached when touched. The New World species (four genera in family Erethizontidae) are arboreal and have barbed quills; the Old World species (four genera in family Hystricidae) are terrestrial and have unbarbed quills. The North American porcupine (Erethizon dorsatum), about 31 in. (80 cm) long with a tail about 12 in. (30 cm) long and quills about 3 in. (8 cm) long, drives its powerful tail against an assailant. For food, it favours the tender tissue beneath tree bark. Crested porcupines, the typical Old World porcupines, run backward, quills erect, into the enemy. They eat roots, fruit, and other vegetation. The African crested porcupine, the largest terrestrial rodent in Europe and Africa, may weigh 60 lb (27 kg) and have quills 14 in. (35 cm) long
Any of various tropical marine fishes of the family Diodontidae, having strong sharp spines on the body and capable of inflating themselves when attacked