Claw: Wikis

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A domestic cat's protractible claw

A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. However, the word "claw" is also often used in reference to an invertebrate. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end of the leg or tarsus for gripping a surface as the creature walks. Crab's and lobster's pincers, or more formally, their "chelae," are sometimes called claws.

A claw is made of hard protein called keratin. Claws are used to catch and hold prey in carnivorous mammals such as cats and dogs, but may also be used for such purposes as digging, climbing trees, etc, in those and other species.

Similar appendages which are flat and do not come to a sharp point are called nails instead.

Contents

Arthropods

The correct term for an arthropod's 'claw' is a chela (plural chelae). Legs bearing a chela are called chelipeds. Chelae are also called pincers.

Tetrapods

The claws of Tyrannosaurus are among the largest recorded

In tetrapods, claws are made of keratin and consist of two layers. The unguis is the harder external layer, which consists of keratin fibers arranged perpendicular to the direction of growth and in layers at an oblique angle. The subunguis is the softer, flaky underside layer whose grain is parallel to the direction of growth. The claw grows outward from the nail matrix at the base of the unguis and the subunguis grows thicker while travelling across the nail bed. The unguis grows outward faster than the subunguis to produce a curve and the thinner sides of the claw wear away faster than their thicker middle, producing a more or less sharp point. Tetrapods use their claws in many ways, commonly to grasp or kill prey, to dig and to climb and hang.

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Birds

A talon is the claw of a bird of prey, its primary hunting tool. The talons are very important; without them, most birds of prey would not be able to catch their food.

Mammals

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 bear weight is called a 'hoof' (see also Horse hoof. However, one side of the cloven-hoof of artiodactyl ungulates may also be called a claw).

A claw sheath from a cat

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 working old unguis layers off on wood or on boards made for the purpose. Ungulates' hooves wear or self-trim by ground contact. Domesticated equids (horses, donkeys and mules) usually need regular trimming by a farrier, as a consequence of reduced activity on hard ground.

Many predatory mammals have protractile claws that can partially hide inside the animal's paw, especially the Felidae, where almost all of its members have fully protractible claws.

Primates

A primate's nail consists of the unguis alone; the subunguis has disappeared. Much like the tail, the claw in apes is no longer necessary. However, in some individuals the subunguis has redeveloped to form a claw-like structure. These individuals do not have actual claws; instead the unguis appears normal with the addition of a thick growth of subunguis. However, some lemurs do possess toilet-claws.

See also

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Simple English


A claw is a sharp object. It is found at the end of a toe or finger in many mammals, birds, and some reptiles. The word "claws" is most often used in reference to an invertebrate. For example, the crab's and lobster's claws or pincers.

A claw is made of hard protein called keratin. They are used by some meat eating mammals such as cats and dogs to catch and hold prey, but they may also be used for other things such as digging, climbing trees, and so on, in those and other species.

Similar appendages that are flat and do not come to a sharp point are called nails instead.

Contents

Arthropods

The correct name for an arthropod's 'claw' is chela (plural chelae). Legs that have a chela are called chelipeds. Chelae are also called pincers.

Tetrapods

Tetrapods, claws are made of keratin and have of two layers. The unguis is the outside hard layer, which has keratin fibers arranged perpendicular to the direction of growth and in layers at an angle. The subunguis is the soft, flaky layer, and the grain is parallel to the direction of growth. The claw grows outward from the nail matrix at the base of the unguis and the subunguis grows thicker while traveling across the nail bed. The unguis grows outward faster than the subunguis to make a curve and the thinner sides of the claw wear away faster than their thicker middle, making a more or less sharp point. Tetrapods use their claws in many ways, such as grasping or killing prey, digging, climbing, and hanging.

Birds

A talon is the claw of a bird of prey,which it uses to hunt. The talons are very important, and if they did not have them, most birds would not be able to catch their food.

Mammals

A nail is similar to a claw but it is flatter and has a curved edge instead of a point. A nail that is big enough to hold weight is called a 'hoof' (see also Horse hoof.


Every so often, the growth of claws stops and restarts, just like the growth of hair. In hair, this causes the hair to fall out and it is replaced by a new one. In claws, this results in an old layer, and it breaks off. This takes several months for human thumbnails. Cats are often seen working old layers off on wood or on boards made for the purpose. Ungulates' hoovestrim themselves when they walk on the ground. Domesticated equids (horses, donkeys and mules) usually need regular trimming by a farrier.

Many predatory mammals have claws that can hide inside the animal's paw, especially animals such as the cat.

Primates

A primate's nail only has the unguis; the subunguis has disappeared. Similar to the tail, the claw in apes is not needed. However, in some primates the subunguis has redeveloped to make a claw-like structure. These certain animals do not have actual claws, instead the unguis appears normal along with a thick growth of subunguis. However some lemurs have a toilet-claw.

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