A pentadactyl limb is a limb with five digits (fingers or toes), characteristic
of four-legged vertebrates. It is generally
used for locomotion and is found in amphibians, reptiles, birds,
and mammals, but may be greatly modified
(as in the flippers of seals or whales or the wings of bats). It probably
evolved from the fins of primitive fish, which are the only modern vertebrates
not to retain it.
|The feet of mammals have evolved in many different
ways from the basic mammalian foot (A), possessed by the earliest
shrew-like mammal. Seals (B) have developed evenly graduated toes
for a webbed paddle. Moles (C) have truncated toes for leverage when
digging. The camel's two toes (D) are padded for walking on sand.
Horses have a hoof (E) instead of claws, and elongated feet for speed,
as has the cheetah (F). Bats (G) have enormously elongated digits
to support wings. Kangaroos' toes (H) are designed for hopping. Lemurs
(I) and sloths (J) have forelimbs for grasping trees.