sets of incisor teeth, one behind the other. This way they can be distinguished from rodents, with which they are often confused. Carl Linnaeus originally grouped rabbits and rodents under the class Glires; later, they were separated as the scientific consensus is that many of their similarities were a result of convergent evolution. Recent DNA analysis and the discovery of a common ancestor has supported the view that they share a common lineage, so rabbits and rodents are now often grouped together in the superorder Glires. Morphology Since speed and agility are a rabbit's main defenses against predators (including the swift fox), rabbits have large hind leg bones and well-developed musculature. Though plantigrade at rest, rabbits are on their toes while running, assuming a more digitigrade posture. Rabbits use their strong claws for digging and (along with their teeth) for defense. Each front foot has four toes plus a dewclaw. Each hind foot has four toes (but no dewclaw). Most wild rabbits (especially compared to hares) have relatively full, egg-shaped bodies. The soft coat of the wild rabbit is agouti in coloration (or, rarely, melanistic), which aids in camouflage. The tail of the rabbit (with the exception of the cottontail species) is dark on top and white below. Cottontails have white on the top of their tails. As a result of the position of the eyes in its skull, the rabbit has a field of vision that encompasses nearly 360 degrees, with just a small blind spot at the bridge of the nose. Hind limb elements The anatomy of rabbits' hind limbs are structurally similar to that of other land mammals and contribute to their specialized form of locomotion. The bones of the hind limbs consist of long bones (the femur, tibia, fibula, and phalanges) as well as short bones (the tarsals). These bones are created through endochondral ossification during development. Like most land mammals, the round head of the femur articulates with the acetabulum of the os coxae. The femur articulates with the tibia, but not the fibula, which is fused to the tibia. The tibia and fibula articulate with the tarsals of the pes, commonly called the foot. The hind limbs of the rabbit are longer than the front limbs. This allows them to produce their hopping form of locomotion. Longer hind limbs are more capable of producing faster speeds. Hares, which have longer legs than cottontail rabbits,