Old World and New World porcupines evolved their quills separately
Porcupines on different continents look like close cousins, but they are not. The spiny rodents of Africa and Asia and the tree-climbing ones of the Americas grew their quills independently, a textbook case of convergent evolution. American porcupines are actually closer to several other rodent families than to their Old World namesakes.
Twenty-nine species share the name, split between two families within a large rodent group called the hystricognaths. The largest porcupine ranks as the world's third-biggest living rodent after the capybara and the beaver. Most are 60 to 90 centimetres long, weigh 5 to 16 kilograms, and are round, slow and coloured in browns, greys and whites. Their quills are modified hairs made of keratin, and they serve as a warning, a strategy biologists call aposematism. Hedgehogs, echidnas and tenrecs arrived at similar spiny armour on their own too.
The 11 Old World species live in Italy, western and southern Asia and much of Africa. They are large, ground-dwelling and strictly nocturnal, with spines arranged in clusters. The oldest known Asian fossil, Hystrix lufengensis, is about 8 million years old. New World porcupines range across North America and northern South America; they are mostly smaller, climb well, and some species spend their whole lives in trees. Their quills grow singly, and the North American porcupine can reach about 85 centimetres and 18 kilograms.
The quills differ in engineering. American ones are stiff and narrow with a round cross-section, so they drive deeper into an attacker before snapping near the base. Old World spines are hollowed on one face, briefer and more pliable, and they give way nearer the point, much like those of spiny mice and rats.
Molecular studies suggest the lineages leading to Old World porcupines and to the South American group that includes New World porcupines split some 63 to 43 million years ago. Newborns, called porcupettes, arrive with soft quills that harden within days. The name comes from Latin for pig and spine, and some Americans still say quill-pig.
Source: Porcupine
