Urson
The two subfamilies of New World porcupines are mostly smaller (although the North American porcupine reaches about in length and ), 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 rodents than they are to the Old World porcupines.