The Pentadactyl Limb
BatIn the bat their pentadactyl limb has evolved for flight as four digits of the limb have elongated dramatically and grown a sheath of membrane to form wings and the claw like first digit remains outside of flesh to hold on to trees and such when dangling and to hold food.
An example of a bat wing anatomy showing the four elongated bones of the limb and the protruding claw.
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HorseHorses used to have four fleshy toes on the soft terrain, but the terrain changed to harder ground and their toes became hard and small until there was one large toe that became a keratin covered hoof to move rapidly along the hard ground. The hoof is equivalent to a middle finger and the knee a wrist.
An example of the earlier horse limbs along with the modern one showing the lack of extra digits the earlier equines had.
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