A porcupine is any of 29 species of rodent belonging to the families Erethizontidae (genera: Coendou, Sphiggurus, Erethizon, Echinoprocta, and Chaetomys) or Hystricidae (genera: Atherurus, Hystrix, and Trichys). Porcupines vary in size considerably: Rothschild's Porcupine of South America weighs less than a kilogram (2.2 lb); the Crested porcupine found in Italy, Sicily, North Africa and sub-Saharan Africa can grow to well over 27 kg (60 lb). The two families of porcupines are quite different, and although both belong to the Hystricognathi branch of the vast order Rodentia, they are not closely related.
The eleven Old World porcupines tend to be fairly big, and have spikes that are grouped in clusters.
The two subfamilies of New World porcupines are mostly smaller (although the North American Porcupine reaches about 85 cm or 33 in in length and 18 kg or 40 lb), have their quills attached singly rather than grouped in clusters, and are excellent climbers, spending much of their time in trees. The New World porcupines evolved their spines independently (through convergent evolution) and are more closely related to several other families of rodent than they are to the Old World porcupines. Porcupines have a relatively high longevity and had held the record for being the longest-living rodent, until it was recently broken by the Naked mole rat.
