In ecology, a niche is the match of a species to a specific environmental condition. It describes how an organism or population responds to the distribution of resources and competitors and how it in turn alters those same factors. "The type and number of variables comprising the dimensions of an environmental niche vary from one species to another the relative importance of particular environmental variables for a species may vary according to the geographic and biotic contexts". A Grinnellian niche is determined by the habitat in which a species lives and its accompanying behavioral adaptations. An Eltonian niche emphasizes that a species not only grows in and responds to an environment, it may change the environment and its behavior as it grows; the Hutchinsonian niche uses mathematics and statistics to try to explain how species coexist within a given community. The concept of ecological niche is central to ecological biogeography, which focuses on spatial patterns of ecological communities.
"Species distributions and their dynamics over time result from properties of the species, environmental variation... and interactions between the two—in particular the abilities of some species our own, to modify their environments and alter the range dynamics of many other species." Alteration of an ecological niche by its inhabitants is the topic of niche construction. The majority of species exist in a standard ecological niche, sharing behaviors and functional traits similar to the other related species within the same broad taxonomic class, but there are exceptions. A premier example of a non-standard niche filling species is the flightless, ground-dwelling kiwi bird of New Zealand, which feeds on worms and other ground creatures, lives its life in a mammal-like niche. Island biogeography can help associated unfilled niches; the ecological meaning of niche comes from the meaning of niche as a recess in a wall for a statue, which itself is derived from the Middle French word nicher, meaning to nest.
The term was coined by the naturalist Roswell Hill Johnson but Joseph Grinnell was the first to use it in a research program in 1917, in his paper "The niche relationships of the California Thrasher". The Grinnellian niche concept embodies the idea that the niche of a species is determined by the habitat in which it lives and its accompanying behavioral adaptations. In other words, the niche is the sum of the habitat requirements and behaviors that allow a species to persist and produce offspring. For example, the behavior of the California thrasher is consistent with the chaparral habitat it lives in—it breeds and feeds in the underbrush and escapes from its predators by shuffling from underbrush to underbrush. Its'niche' is defined by the felicitous complementing of the thrasher's behavior and physical traits with this habitat; this perspective of niche allows for the existence of empty niches. An ecological equivalent to an organism is an organism from a different taxonomic group exhibiting similar adaptations in a similar habitat, an example being the different succulents found in American and African deserts and euphorbia, respectively.
As another example, the anole lizards of the Greater Antilles are a rare example of convergent evolution, adaptive radiation, the existence of ecological equivalents: the anole lizards evolved in similar microhabitats independently of each other and resulted in the same ecomorphs across all four islands. In 1927 Charles Sutherland Elton, a British ecologist, defined a niche as follows: "The'niche' of an animal means its place in the biotic environment, its relations to food and enemies."Elton classified niches according to foraging activities: For instance there is the niche, filled by birds of prey which eat small animals such as shrews and mice. In an oak wood this niche is filled by tawny owls, while in the open grassland it is occupied by kestrels; the existence of this carnivore niche is dependent on the further fact that mice form a definite herbivore niche in many different associations, although the actual species of mice may be quite different. Conceptually, the Eltonian niche introduces the idea of a species' response to and effect on the environment.
Unlike other niche concepts, it emphasizes that a species not only grows in and responds to an environment based on available resources and climatic conditions, but changes the availability and behavior of those factors as it grows. In an extreme example, beavers require certain resources in order to survive and reproduce, but construct dams that alter water flow in the river where the beaver lives. Thus, the beaver affects the biotic and abiotic conditions of other species that live in and near the watershed. In a more subtle case, competitors that consume resources at different rates can lead to cycles in resource density that differ between species. Not only do species grow differently with respect to resource density, but their own population growth can affect resource density over time; the Hutchinsonian niche is an "n-dimensional hypervolume", where the dimensions are environmental conditions and resources, that define the requirements of an individual or a species to practice "its" way of life, more for its population to persist.
The "hypervolume" defines the multi-dimensional space of resources available to organisms, "all species
New Mexico is a state in the Southwestern region of the United States of America. It is one of the Mountain States and shares the Four Corners region with Utah and Arizona. With a population around two million, New Mexico is the 36th state by population. With a total area of 121,592 sq mi, it is the fifth-largest and sixth-least densely populated of the 50 states. Due to their geographic locations and eastern New Mexico exhibit a colder, alpine climate, while western and southern New Mexico exhibit a warmer, arid climate; the economy of New Mexico is dependent on oil drilling, mineral extraction, dryland farming, cattle ranching, lumber milling, retail trade. As of 2016–2017, its total gross domestic product was $95 billion with a GDP per capita of $45,465. New Mexico's status as a tax haven yields low to moderate personal income taxes on residents and military personnel, gives tax credits and exemptions to favorable industries; because of this, its film industry contributed $1.23 billion to its overall economy.
Due to its large area and economic climate, New Mexico has a large U. S. military presence marked notably with the White Sands Missile Range. Various U. S. national security agencies base their research and testing arms in New Mexico such as the Sandia and Los Alamos National Laboratories. During the 1940s, Project Y of the Manhattan Project developed and built the country's first atomic bomb and nuclear test, Trinity. Inhabited by Native Americans for many thousands of years before European exploration, it was colonized by the Spanish in 1598 as part of the Imperial Spanish viceroyalty of New Spain. In 1563, it was named Nuevo México after the Aztec Valley of Mexico by Spanish settlers, more than 250 years before the establishment and naming of the present-day country of Mexico. After Mexican independence in 1824, New Mexico became a Mexican territory with considerable autonomy; this autonomy was threatened, however, by the centralizing tendencies of the Mexican government from the 1830s onward, with rising tensions leading to the Revolt of 1837.
At the same time, the region became more economically dependent on the United States. At the conclusion of the Mexican–American War in 1848, the United States annexed New Mexico as the U. S. New Mexico Territory, it was admitted to the Union as the 47th state on January 6, 1912. Its history has given New Mexico the highest percentage of Hispanic and Latino Americans, the second-highest percentage of Native Americans as a population proportion. New Mexico is home to part of the Navajo Nation, 19 federally recognized Pueblo communities of Puebloan peoples, three different federally recognized Apache tribes. In prehistoric times, the area was home to Ancestral Puebloans and the modern extant Comanche and Utes inhabited the state; the largest Hispanic and Latino groups represented include the Hispanos of New Mexico and Mexican Americans. The flag of New Mexico features the state's Spanish origins with the same scarlet and gold coloration as Spain's Cross of Burgundy, along with the ancient sun symbol of the Zia, a Puebloan tribe.
These indigenous, Mexican and American frontier roots are reflected in the eponymous New Mexican cuisine and the New Mexico music genre. New Mexico received its name long before the present-day nation of Mexico won independence from Spain and adopted that name in 1821. Though the name “Mexico” itself derives from Nahuatl, in that language it referred to the heartland of the Empire of the Mexicas in the Valley of Mexico far from the area of New Mexico, Spanish explorers used the term “Mexico” to name the region of New Mexico in 1563. In 1581, the Chamuscado and Rodríguez Expedition named the region north of the Rio Grande "San Felipe del Nuevo México"; the Spaniards had hoped to find wealthy indigenous Mexica cultures there similar to those of the Aztec Empire of the Valley of Mexico. The indigenous cultures of New Mexico, proved to be unrelated to the Mexicas, they were not wealthy, but the name persisted. Before statehood, the name "New Mexico" was applied to various configurations of the U.
S. territory, to a Mexican state, to a province of New Spain, all in the same general area, but of varying extensions. With a total area of 121,699 square miles, the state is the fifth-largest state of the US, larger than British Isles. New Mexico's eastern border lies along 103°W longitude with the state of Oklahoma, 2.2 miles west of 103°W longitude with Texas. On the southern border, Texas makes up the eastern two-thirds, while the Mexican states of Chihuahua and Sonora make up the western third, with Chihuahua making up about 90% of that; the western border with Arizona runs along the 109° 03'W longitude. The southwestern corner of the state is known as the Bootheel; the 37°N parallel forms the northern boundary with Colorado. The states of New Mexico, Colorado and Utah come together at the Four Corners in New Mexico's northwestern corner. New Mexico has no natural water sources
Scrotifera is a clade of placental mammals that comprises the following orders and their common ancestors: Chiroptera, Pholidota and Cetartiodactyla, with the latter including the traditional orders Artiodactyla and Cetacea. Scrotifera is the sister group to the Eulipotyphla and together they make up the Laurasiatheria. Peter Waddell of the Institute of Statistical Mathematics, explains the etymology of the clade's name as follows: The name comes from the word scrotum, a pouch in which the testes permanently reside in the adult male. All members of the group have a postpenile scrotum prominently displayed, except for some aquatic forms and pangolin, it appears to be an ancestral character for this group, yet other orders lack this as an ancestral feature, with the probable exception of Primates. The clade Scrotifera is based on evidence from molecular phylogenetics; the monophyly of the group is well supported, although recent studies have indicated that the Pegasoferae is not a natural grouping.
Scavengers are animals that consume dead organisms that have died from causes other than predation. While scavenging refers to carnivores feeding on carrion, it is a herbivorous feeding behavior. Scavengers play an important role in the ecosystem by consuming dead plant material. Decomposers and detritivores complete this process, by consuming the remains left by scavengers. Scavengers aid in overcoming fluctuations of food resources in the environment; the process and rate of scavenging is affected by both biotic and abiotic factors, such as carcass size, habitat and seasons. Scavenger is an alteration of scavager, from Middle English skawager meaning "customs collector", from skawage meaning "customs", from Old North French escauwage meaning "inspection", from schauwer meaning "to inspect", of Germanic origin. Obligate scavenging is rare among vertebrates, due to the difficulty of finding enough carrion without expending too much energy. In vertebrates, only vultures and some pterosaurs are obligate scavengers, as terrestrial soaring flyers are the only animals able to find enough carrion.
Well-known invertebrate scavengers of animal material include burying beetles and blowflies, which are obligate scavengers, yellowjackets. Most scavenging animals are facultative scavengers that gain most of their food through other methods predation. Many large carnivores that hunt such as hyenas and jackals, but animals thought of as scavengers, such as African lions and wolves will scavenge if given the chance, they may use their size and ferocity to intimidate the original hunters. All scavengers above insect size are predators and will hunt if not enough carrion is available, as few ecosystems provide enough dead animals year-round to keep its scavengers fed on that alone. Scavenging wild dogs and crows exploit roadkill. Scavengers of dead plant material include termites that build nests in grasslands and collect dead plant material for consumption within the nest; the interaction between scavenging animals and humans is seen today most in suburban settings with animals such as opossums and raccoons.
In some African towns and villages, scavenging from hyenas is common. In the prehistoric eras, the species Tyrannosaurus rex may have been an apex predator, preying upon hadrosaurs and juvenile sauropods, although some experts have suggested the dinosaur was a scavenger; the debate about whether Tyrannosaurus was an apex predator or scavenger was among the longest ongoing feuds in paleontology. Recent research shows that while an adult Tyrannosaurus rex would energetically gain little though scavenging, smaller theropods of 500 kg may have gained levels similar to that of hyenas, though not enough for them to rely on scavenging. There are an info that Otodus megalodon, Ceratosaurus and some more prehistoric animals were scavengers. Animals which consume feces, such as dung beetles, are referred to as coprovores. Animals that collect small particles of dead organic material of both animal and plant origin are referred to as detritivores. Scavengers play a fundamental role in the environment through the removal of decaying organisms, serving as a natural sanitation service.
While microscopic and invertebrate decomposers break down dead organisms into simple organic matter which are used by nearby autotrophs, scavengers help conserve energy and nutrients obtained from carrion within the upper trophic levels, are able to disperse the energy and nutrients farther away from the site of the carrion than decomposers. Scavenging unites animals which would not come into contact, results in the formation of structured and complex communities which engage in nonrandom interactions. Scavenging communities function in the redistribution of energy obtained from carcasses and reducing diseases associated with decomposition. Oftentimes, scavenger communities differ in consistency due to carcass size and carcass types, as well as by seasonal effects as consequence of differing invertebrate and microbial activity. Competition for carrion results in the inclusion or exclusion of certain scavengers from access to carrion, shaping the scavenger community; when carrion decomposes at a slower rate during cooler seasons, competitions between scavengers decrease, while the number of scavenger species present increases.
Alterations in scavenging communities may result in drastic changes to the scavenging community in general, reduce ecosystem services and have detrimental effects on animal and humans. The reintroduction of gray wolves into Yellowstone National Park in the United States caused drastic changes to the prevalent scavenging community, resulting in the provision of carrion to many mammalian and avian species; the reduction of vulture species in India lead to the increase of opportunistic species such as feral dogs and rats. The presence of both species at carcasses resulted in the increase of diseases such as rabies and bubonic plague in wildlife and livestock, as feral dogs and rats are transmitters of such diseases. Furthermore, the decline of vulture populations in India has been linked to the increased rates of anthrax in humans due to the handling and ingestion of infected livestock carcasses. An increase of disease transmission has been observed in mammalian scavengers in Kenya due to the decrease in vulture populations in the ar
The Triassic is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.9 million years ago, to the beginning of the Jurassic Period 201.3 Mya. The Triassic is the shortest period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. Triassic began in the wake of the Permian–Triassic extinction event, which left the Earth's biosphere impoverished. Therapsids and archosaurs were the chief terrestrial vertebrates during this time. A specialized subgroup of archosaurs, called dinosaurs, first appeared in the Late Triassic but did not become dominant until the succeeding Jurassic Period; the first true mammals, themselves a specialized subgroup of therapsids evolved during this period, as well as the first flying vertebrates, the pterosaurs, like the dinosaurs, were a specialized subgroup of archosaurs. The vast supercontinent of Pangaea existed until the mid-Triassic, after which it began to rift into two separate landmasses, Laurasia to the north and Gondwana to the south.
The global climate during the Triassic was hot and dry, with deserts spanning much of Pangaea's interior. However, the climate became more humid as Pangaea began to drift apart; the end of the period was marked by yet another major mass extinction, the Triassic–Jurassic extinction event, that wiped out many groups and allowed dinosaurs to assume dominance in the Jurassic. The Triassic was named in 1834 by Friedrich von Alberti, after the three distinct rock layers that are found throughout Germany and northwestern Europe—red beds, capped by marine limestone, followed by a series of terrestrial mud- and sandstones—called the "Trias"; the Triassic is separated into Early and Late Triassic Epochs, the corresponding rocks are referred to as Lower, Middle, or Upper Triassic. The faunal stages from the youngest to oldest are: During the Triassic all the Earth's land mass was concentrated into a single supercontinent centered more or less on the equator and spanning from pole to pole, called Pangaea.
From the east, along the equator, the Tethys sea penetrated Pangaea, causing the Paleo-Tethys Ocean to be closed. In the mid-Triassic a similar sea penetrated along the equator from the west; the remaining shores were surrounded by the world-ocean known as Panthalassa. All the deep-ocean sediments laid down during the Triassic have disappeared through subduction of oceanic plates; the supercontinent Pangaea was rifting during the Triassic—especially late in that period—but had not yet separated. The first nonmarine sediments in the rift that marks the initial break-up of Pangaea, which separated New Jersey from Morocco, are of Late Triassic age. S. these thick sediments comprise the Newark Group. Because a super-continental mass has less shoreline compared to one broken up, Triassic marine deposits are globally rare, despite their prominence in Western Europe, where the Triassic was first studied. In North America, for example, marine deposits are limited to a few exposures in the west, thus Triassic stratigraphy is based on organisms that lived in lagoons and hypersaline environments, such as Estheria crustaceans.
At the beginning of the Mesozoic Era, Africa was joined with Earth's other continents in Pangaea. Africa shared the supercontinent's uniform fauna, dominated by theropods and primitive ornithischians by the close of the Triassic period. Late Triassic fossils are more common in the south than north; the time boundary separating the Permian and Triassic marks the advent of an extinction event with global impact, although African strata from this time period have not been studied. During the Triassic peneplains are thought to have formed in what is now southern Sweden. Remnants of this peneplain can be traced as a tilted summit accordance in the Swedish West Coast. In northern Norway Triassic peneplains may have been buried in sediments to be re-exposed as coastal plains called strandflats. Dating of illite clay from a strandflat of Bømlo, southern Norway, have shown that landscape there became weathered in Late Triassic times with the landscape also being shaped during that time. At Paleorrota geopark, located in Rio Grande do Sul, the Santa Maria Formation and Caturrita Formations are exposed.
In these formations, one of the earliest dinosaurs, Staurikosaurus, as well as the mammal ancestors Brasilitherium and Brasilodon have been discovered. The Triassic continental interior climate was hot and dry, so that typical deposits are red bed sandstones and evaporites. There is no evidence of glaciation near either pole. Pangaea's large size limited the moderating effect of the global ocean; the strong contrast between the Pangea supercontinent and the global ocean triggered intense cross-equatorial monsoons. The Triassic may have been a dry period, but evidence exists that it was punctuated by several episodes of increased rainfall in tropical and subtropical latitudes of the Tethys Sea and its surrounding land. Sediments and fossils suggestive of a more humid climate are known from the Anisian to Ladinian of the Tethysian domain, from the Carnian and Rhaetian of a larger area that includes the Boreal domain, the North
North America is a continent within the Northern Hemisphere and all within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, to the southeast by South America and the Caribbean Sea. North America covers an area of about 24,709,000 square kilometers, about 16.5% of the earth's land area and about 4.8% of its total surface. North America is the third largest continent by area, following Asia and Africa, the fourth by population after Asia and Europe. In 2013, its population was estimated at nearly 579 million people in 23 independent states, or about 7.5% of the world's population, if nearby islands are included. North America was reached by its first human populations during the last glacial period, via crossing the Bering land bridge 40,000 to 17,000 years ago; the so-called Paleo-Indian period is taken to have lasted until about 10,000 years ago. The Classic stage spans the 6th to 13th centuries.
The Pre-Columbian era ended in 1492, the transatlantic migrations—the arrival of European settlers during the Age of Discovery and the Early Modern period. Present-day cultural and ethnic patterns reflect interactions between European colonists, indigenous peoples, African slaves and their descendants. Owing to the European colonization of the Americas, most North Americans speak English, Spanish or French, their culture reflects Western traditions; the Americas are accepted as having been named after the Italian explorer Amerigo Vespucci by the German cartographers Martin Waldseemüller and Matthias Ringmann. Vespucci, who explored South America between 1497 and 1502, was the first European to suggest that the Americas were not the East Indies, but a different landmass unknown by Europeans. In 1507, Waldseemüller produced a world map, in which he placed the word "America" on the continent of South America, in the middle of what is today Brazil, he explained the rationale for the name in the accompanying book Cosmographiae Introductio:... ab Americo inventore... quasi Americi terram sive Americam.
For Waldseemüller, no one should object to the naming of the land after its discoverer. He used the Latinized version of Vespucci's name, but in its feminine form "America", following the examples of "Europa", "Asia" and "Africa". Other mapmakers extended the name America to the northern continent, In 1538, Gerard Mercator used America on his map of the world for all the Western Hemisphere; some argue that because the convention is to use the surname for naming discoveries, the derivation from "Amerigo Vespucci" could be put in question. In 1874, Thomas Belt proposed a derivation from the Amerrique mountains of Central America. Marcou corresponded with Augustus Le Plongeon, who wrote: "The name AMERICA or AMERRIQUE in the Mayan language means, a country of perpetually strong wind, or the Land of the Wind, and... the can mean... a spirit that breathes, life itself." The United Nations formally recognizes "North America" as comprising three areas: Northern America, Central America, The Caribbean.
This has been formally defined by the UN Statistics Division. The term North America maintains various definitions in accordance with context. In Canadian English, North America refers to the land mass as a whole consisting of Mexico, the United States, Canada, although it is ambiguous which other countries are included, is defined by context. In the United States of America, usage of the term may refer only to Canada and the US, sometimes includes Greenland and Mexico, as well as offshore islands. In France, Portugal, Romania and the countries of Latin America, the cognates of North America designate a subcontinent of the Americas comprising Canada, the United States, Mexico, Greenland, Saint Pierre et Miquelon, Bermuda. North America has been referred to by other names. Spanish North America was referred to as Northern America, this was the first official name given to Mexico. Geographically the North American continent has many subregions; these include cultural and geographic regions. Economic regions included those formed by trade blocs, such as the North American Trade Agreement bloc and Central American Trade Agreement.
Linguistically and culturally, the continent could be divided into Latin America. Anglo-America includes most of Northern America and Caribbean islands with English-speaking populations; the southern North American continent is composed of two regions. These are the Caribbean; the north of the continent maintains recognized regions as well. In contrast to the common definition of "North America", which encompasses the whole continent, the term "North America" is sometimes used to refer only to Mexico, the United States, Greenland; the term Northern America refers to the northern-most countries and territories of North America: the United States, Bermuda, St. Pierre and Miquelon and Greenland. Although the term does not refer to a unifie
A claw is a curved, pointed appendage, found at the end of a toe or finger in most amniotes. Some invertebrates such as beetles and spiders have somewhat similar fine hooked structures at the end of the leg or tarsus for gripping a surface as the creature walks. Crabs', lobsters' and scorpions' pincers, or more formally, their chelae, are sometimes called claws. A true 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 be used for such purposes as digging, climbing trees, self-defense, grooming, in those and other species. Similar appendages that are flat and do not come to a sharp point are called nails instead. Claw-like projections that do not form at the end of digits, but spring from other parts of the foot are properly named spurs. In tetrapods, claws 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 to grasp or kill prey, to dig and to climb and hang. All Carnivora have claws, which vary in length and shape. Claws are made of keratin. Many predatory mammals have protractile claws that can hide inside the animal's paw the cat family, Felidae all of whose members have protractible claws. Outside of the cat family, retractable claws are found only in certain species of the Viverridae. A claw, retractable is protected from wear and tear. Most cats and dogs have a dewclaw on the inside of the front paws, it does help the cats to grasp prey.
Because the dew claw does not touch the ground, it receives less wear and tends to be sharper and longer. A nail is flatter and has a curved edge instead of a point. A nail, big enough to bear weight is called a "hoof".. Every so the growth of claws stops and restarts, as does hair. In a hair, this results in the hair being replaced by a new one. In claws, this results in an abscission layer, the old segment breaks off; this process takes several months for human thumbnails. Cats are seen working old unguis layers off on wood or on boards made for the purpose. Ungulates' hooves self-trim by ground contact. Domesticated equids need regular trimming by a farrier, as a consequence of reduced activity on hard ground. Primate nails consist of the unguis alone. With the evolution of grasping hands and feet, claws are no longer necessary for locomotion, instead most digits exhibit nails. However, claw-like nails are found in small-bodied callitrichids on all digits except the hallux or big toe. A laterally flattened grooming claw, used for grooming, can be found on the second toe in living strepsirrhines, the second and third in tarsiers.
Aye-ayes have functional claws on all other digits except the hallux, including a grooming claw on the second toe. Less known, a grooming claw is found on the second pedal digit of night monkeys and other New World monkeys. Most reptiles have well-developed claws. Most lizards have toes ending in stout claws. In snakes and claws are absent, but in many boids such as Boa constrictor, remnants of 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, in holding down prey in carnivorous species. A talon is the claw of a bird of its primary hunting tool; the talons are important. Some birds use claws for defensive purposes. Cassowaries use claws on their inner toe for defence, have been known to disembowel people. All birds however have claws, which are used as general holdfasts and protection for the tip of the digits; the hoatzin and turaco are unique among extant birds in having functional claws on the thumb and index finger on the forelimbs as chicks, allowing them to climb trees until the adult plumage with flight feathers develop.
However, several birds have a claw- or nail-like structure hidden under the feathers at the end of the hand digits, notably ostriches, ducks and kiwis. The only amphibians to bear claws are the African clawed frogs. Claws appear to have evolved separately in the amniote line; the scientifically correct term for the "claw" of an arthropod, such as a lobster or crab, is a chela. Legs bearing a chela are called chelipeds. Chelae are called pincers. Horse hoof Dactyly The Horse's Hoof Anatomy Rat's Claws explains much about mammalian claws in general