Porcupines are rodents with a coat of sharp spines, or quills, that defend them from predators. They are indigenous in both the Old World and the New World. Porcupines are the third largest of the rodents, behind the capybara and the beaver.
A porcupine is any of 27 species of rodent belonging to the families Erethizontidae or Hystricidae. Porcupines vary in size considerably: Rothschild’s Porcupine of South America weighs less than a kilogram (2.2 lb (1.00 kg)); the African Porcupine can grow to well over 10 kg (22 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 are almost exclusively terrestrial, tend to be fairly large, and have quills that are grouped in clusters. They are believed to have separated from the other hystricognaths about 30 million years ago, much earlier than the New World porcupines. The twelve New World porcupines are mostly smaller (although the North American Porcupine reaches about 85 cm/33 in in length and 18 kg/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, which was recently broken by the Naked Mole Rat (Heterocephalus glaber).