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A claw is a curved pointed growth found at the end of a toe or finger, or in arthropods, of the tarsus. The claws of arthropods are sometimes called
pincers.
In tetrapods, claws are made of keratin, and consist of two layers: the unguis, which consists of keratin fibers perpendicular to
the direction of growth arranged in layers at an oblique angle, and the subunguis, whose grain is parallel to
the direction of growth.
A nail is homologous to a claw, but is flatter and has a curved edge instead of a point. A nail that is big enough to walk
on is called a hoof.
A talon is the claw of a bird of
prey.
Every so often, the growth of claws stops and restarts, as does hair. In hair, this
results in the hair falling out and being replaced by a new one; in claws, this results in an abscission layer, and the old
segment breaks off. This process takes several months for human thumbnails; cats are often seen doing it on wood or on boards made for the purpose.
Claw is also the name of a 1927 Hollywood motion
picture directed by Sidney Olcott.
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