 Moles have polydactyl forepaws; each has an extra thumb (also known as a prepollex) next to the regular thumb.While the mole's other digits have multiple joints, the prepollex has a single, sickle-shaped bone that develops later and differently from the other fingers during embryogenesis from a transformed sesamoid bone in the wrist, independently evolved but similar to the giant panda thumb.This supernumerary digit is species-specific, as it is not present in shrews, the mole's closest relatives.