A claw is a curved, pointed appendage, found at the end of a toe or finger in most amniotes (mammals and reptiles, including birds). 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. Crabs' and lobsters' 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, self-defense etc., in those and other species.
Similar appendages that are flat and do not come to a sharp point are called nails instead.
Claws of animals like tigers, lions, and bears were used in making items such as ornaments, pendants, and brooches. Tigers' and lions' claws are expensive because it is illegal to trade the parts of such protected animals.
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Arthropods [link]
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 [link]
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.
Amphibians [link]
The only amphibians to bear claws are the African clawed frogs. Claws appear to have evolved separately in the amphibian and amniote line.[1]
Reptiles [link]
Lizards, Turtles, and Crocodylians [link]
Most lizards have toes ending in stout claws. The claws form from the last scale on the toe.[2] Most reptiles have well-developed claws. In snakes, feet and claws are absent, but in many boids such as Boa constrictor, remnants of highly reduced hind-limbs emerge with a single claw as "spurs" on each side of the anal opening.
Lizard claws are used as aids in climbing, and in holding down prey in carnivorous species.
Birds [link]
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. Some birds also use claws for defensive purposes. Cassowaries use claws on their inner toe (digit II) for defence, and have been known to seriously injure people. All birds however have claws, which are used as general holdfasts and protection for the tip of the digits.
The hoatzin is unique among extant birds in having functional claws on the thumb and index finger (digit I and II) on the forelimbs as chicks, allowing them to climb trees until the adult plumage with flight feathers develop.[3] However, several birds have a claw- or nail-like structure hidden under the feathers at the end of the hand digits, notably ducks, geese and kiwis.[4]
Mammals [link]
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).
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 [link]
Primate nails consist of the unguis alone, as the subunguis has disappeared. With the evolution of grasping hands and feet, claws are no longer necessary for locomotion, and instead most digits exhibit nails. However, claw-like nails are found in small-bodied callitrichids on all digits except the hallux or big toe, and in prosimians, which possess one or two laterally flattened toilet claws, used for grooming. These can be found on the second toe in lemurs and lorises, and the second and third in tarsiers. Aye-ayes have functional claws on all other digits except the hallux, including a toilet claw on the second toe.[5]
References [link]
- ^ Maddin & al. (2009): The anatomy and development of the claws of Xenopus laevis (Lissamphibia: Anura) reveal alternate pathways of structural evolution in the integument of tetrapods. Journal of Anatomy, no 214 (4): pp 607-19 Abstract
- ^ Alibardi, L. (2008): Microscopic analysis of lizard claw morphogenesis and hypothesis on its evolution. Acta Zoologica: Morphology and Evolution, vol 89 (2): pp 169–178. abstract
- ^ Parker, W. K. (1891). "On the Morphology of a Reptilian Bird, Opisthocomus hoazin". Transactions of the Zoological Society of London 13: 43–89. DOI:10.1111/j.1096-3642.1891.tb00045.x. https://biodiversitylibrary.org/page/31083330.
- ^ Sir Walter Lawry Buller (1888): A History of the Birds of New Zealand. London excerpt from Zealand Electronic Text Centre collection
- ^ Soligo, C., Müller, A.E. (1999). "Nails and claws in primate evolution". Journal of Human Evolution 36 (1): 97–114. DOI:10.1006/jhev.1998.0263. PMID 9924135.
See also [link]
External links [link]
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Wikimedia Commons has media related to: Claws |
- The Horse's Hoof Anatomy
- Rat's Claws, also explains much about mammalian claws in general.
https://wn.com/Claw
Claw-free permutation
In mathematical and computer science field of cryptography, a group of three numbers (x,y,z) is said to be a claw of two permutations f0 and f1 if
A pair of permutations f0 and f1 are said to be claw-free if there is no efficient algorithm for computing a claw.
The terminology claw free was introduced by Goldwasser, Micali, and Rivest in their 1984 paper, "A Paradoxical Solution to the Signature Problem" (and later in a more complete journal paper), where they showed that the existence of claw-free pairs of trapdoor permutations implies the existence of digital signature schemes secure against adaptive chosen-message attack. This construction was later superseded by the construction of digital signatures from any one-way trapdoor permutation. The existence of trapdoor permutations does not by itself imply claw-free permutations exist; however, it has been shown that claw-free permutations do exist if factoring is hard.
The general notion of claw-free permutation (not necessarily trapdoor) was further studied by Ivan Damgård in his PhD thesis The Application of Claw Free Functions in Cryptography (Aarhus University, 1988), where he showed how to construct Collision Resistant Hash Functions from claw-free permutations. The notion of claw-freeness is closely related to that of collision resistance in hash functions. The distinction is that claw-free permutations are pairs of functions in which it is hard to create a collision between them, while a collision-resistant hash function is a single function in which it's hard to find a collision, i.e. a function H is collision resistant if it's hard to find a pair of distinct values x,y such that
Claw (disambiguation)
A claw is a sharp growth at the end of a toe or finger.
Claw or Claws may also refer to:
In entertainment:
In music
Forming
Forming may refer to:
- Cold forming or work hardening
- Roll forming
See also
Forming (metalworking)
Forming, or metal forming, is the metalworking process of fashioning metal parts and objects through mechanical deformation; the workpiece is reshaped without adding or removing material, and its mass remains unchanged. Forming operates on the materials science principle of plastic deformation, where the physical shape of a material is permanently deformed.
Characteristics
Metal forming tends to have more uniform characteristics across its subprocesses than its contemporary processes, cutting and joining.
On the industrial scale, forming is characterized by:
Forming processes
Forming processes tend to be typified by differences in effective stresses. These categories and descriptions are highly simplified, since the stresses operating at a local level in any given process are very complex and may involve many varieties of stresses operating simultaneously, or it may involve stresses which change over the course of the operation.
Forming (song)
"Forming" is the debut single by American punk rock band Germs. Released on What?, an independent start-up label, in July 1977, it is regarded as the first true Los Angeles punk record.
Germs, comprising four teenagers, formed not long before the recording of the single: David Bowie–worshipping friends Jan Paul Beahm and George Ruthenberg met Belinda Carlisle and Teresa Ryan while staking out Queen's Freddie Mercury at a Beverly Hills motel and decided to start a band. Vocalist Beahm changed his name to Bobby Pyn (he would soon become better known as Darby Crash), guitarist Ruthenberg became Pat Smear, and bassist Ryan transformed into Lorna Doom. Carlisle dropped out when she came down with mononucleosis and never played a live show with the group. She was replaced as drummer by Becky Barton, redubbed Donna Rhia. The band's all-female rhythm section put them—along with X—in the vanguard of women's participation in early L.A. punk, where they would feature in such acts as Bags, The Controllers, Eyes, and the all-female Go-Go's. "Forming" was the band's first composition, written by Pyn after a few rehearsals in the Ruthenberg family garage.
Podcasts:
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by Old Season
The Claw
by: Old SeasonCrawling through all dreams foretold
A hand clasped my heart
Ripping wounds that never heal
All life falls apart
The end of a time has come
The vultures circle round
Rip the flesh - tease
Lie asleep and dream of death
The claw clasped my heart
My thoughts climax
Enamoured of death
My final breath
Take me now I have no fear
Pray the end will soon be near
To die in a dream
The end of a time has come
The vultures circle round
Rip the flesh, bleed
Lie asleep and dream of death
The claw clasps my heart
My thoughts climax
Enamoured of death