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Pentadactyly
In biology, dactyly is the arrangement of digits (fingers and toes) on the hands, feet, or sometimes wings of a tetrapod animal. It comes from the Greek word δακτυλος (''dáktylos'') = "finger". Sometimes the ending "-dactylia" is used. The derived adjectives end with "-dactyl" or "-dactylous". As a normal feature Pentadactyly Pentadactyly (from Greek "five") is the condition of having five digits on each limb. It is traditionally believed that all living tetrapods are descended from an ancestor with a pentadactyl limb, although many species have now lost or transformed some or all of their digits by the process of evolution. However, this viewpoint was challenged by Stephen Jay Gould in his 1991 essay "Eight (Or Fewer) Little Piggies", where he pointed out polydactyly in early tetrapods and described the specializations of digit reduction. Despite the individual variations listed below, the relationship is to the original five-digit model. In reptiles, the limbs ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polydactyly In Early Tetrapods
Polydactyly in stem-tetrapods should here be understood as having more than five digits to the finger or foot, a condition that was the natural state of affairs in the very first stegocephalians during the evolution of terrestriality. The polydactyly in these largely aquatic animals is not to be confused with polydactyly in the medical sense, i.e. it was not an anomaly in the sense it was not a congenital condition of having more than the typical number of digits for a given taxon. Rather, it appears to be a result of the early evolution from a limb with a fin rather than digits. "Living tetrapods, such as the frogs, turtles, birds and mammals, are a subgroup of the tetrapod lineage. The lineage also includes finned and limbed tetrapods that are more closely related to living tetrapods than to living lungfishes." Tetrapods evolved from animals with fins such as found in lobe-finned fishes. From this condition a new pattern of limb formation evolved, where the development axis of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Finger
A finger is a limb of the body and a type of digit, an organ of manipulation and sensation found in the hands of most of the Tetrapods, so also with humans and other primates. Most land vertebrates have five fingers ( Pentadactyly). Chambers 1998 p. 603 Oxford Illustrated pp. 311, 380 Land vertebrate fingers The five-rayed anterior limbs of terrestrial vertebrates can be derived phylogenetically from the pectoral fins of fish. Within the taxa of the terrestrial vertebrates, the basic pentadactyl plan, and thus also the fingers and phalanges, undergo many variations. Morphologically the different fingers of terrestrial vertebrates are homolog. The wings of birds and those of bats are not homologous, they are analogue flight organs. However, the phalanges within them are homologous. Chimpanzees have lower limbs that are specialized for manipulation, and (arguably) have fingers on their lower limbs as well. In the case of Primates in general, the digits of the hand a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scheme Human Hand Bones-en
A scheme is a systematic plan for the implementation of a certain idea. Scheme or schemer may refer to: Arts and entertainment * The Scheme (TV series), ''The Scheme'' (TV series), a BBC Scotland documentary series * The Scheme (band), an English pop band * ''The Scheme'', an action role-playing video game for the PC-8801, made by Quest Corporation * Schemer (comics), Richard Fisk, a Marvel Comics villain turned antihero * Horace Schemer, a fictional character in the TV series ''Shining Time Station'' * Schemee, a fictional child character and Schemer's nephew in the TV Series ''Shining Time Station'' * Schemers (film), ''Schemers'' (film), a Scottish film Other uses * Classification scheme, eg a thesaurus, a Taxonomy (general), taxonomy, a data model, or an Ontology (information science), ontology * Scheme (programming language), a minimalist dialect of Lisp * Scheme (mathematics), a concept in algebraic geometry * Scheme (linguistics), a figure of speech that changes a sentence's ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equidae
Equidae (sometimes known as the horse family) is the taxonomic family of horses and related animals, including the extant horses, asses, and zebras, and many other species known only from fossils. All extant species are in the genus '' Equus'', which originated in North America. Equidae belongs to the order Perissodactyla, which includes the extant tapirs and rhinoceros, and several extinct families. The term equid refers to any member of this family, including any equine. Evolution The oldest known fossils assigned to Equidae were found in North America, and date from the early Eocene epoch, 54 million years ago. They were once assigned to the genus ''Hyracotherium'', but the type species of that genus is now regarded as a palaeothere. The other species have been split off into different genera. These early equids were fox-sized animals with three toes on the hind feet, and four on the front feet. They were herbivorous browsers on relatively soft plants, and already adapte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horse
The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature, ''Eohippus'', into the large, single-toed animal of today. Humans began domesticating horses around 4000 BCE, and their domestication is believed to have been widespread by 3000 BCE. Horses in the subspecies ''caballus'' are domesticated, although some domesticated populations live in the wild as feral horses. These feral populations are not true wild horses, as this term is used to describe horses that have never been domesticated. There is an extensive, specialized vocabulary used to describe equine-related concepts, covering everything from anatomy to life stages, size, colors, markings, breeds, locomotion, and behavior. Horses are adapted to run, allowing them to quickly escape predators, and po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ostriches
Ostriches are large flightless birds of the genus ''Struthio'' in the order Struthioniformes, part of the infra-class Palaeognathae, a diverse group of flightless birds also known as ratites that includes the emus, rheas, and kiwis. There are two living species of ostrich: the common ostrich, native to large areas of sub-Saharan Africa and the Somali ostrich, native to the Horn of Africa. The common ostrich was also historically native to the Arabian Peninsula, and ostriches were present across Asia as far east as Mongolia during the Late Pleistocene and possibly into the Holocene. They lay the largest eggs of any living land animal. With the ability to run at 70 km/h (43.5 mph), they are the fastest birds on land. They are farmed worldwide, particularly for their feathers as they are used as decoration and feather dusters. Their skin is also used for leather products. They are the heaviest living birds. Taxonomic history The genus ''Struthio'' was first described by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Artiodactyla
The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing posteriorly. By contrast, odd-toed ungulates bear weight on an odd number of the five toes. Another difference between the two is that many other even-toed ungulates (with the exception of Suina) digest plant cellulose in one or more stomach chambers rather than in their intestine as the odd-toed ungulates do. Cetaceans (whales, dolphins, and porpoises) evolved from even-toed ungulates, and are therefore often classified under the same taxonomic branch because a species cannot outgrow its evolutionary ancestry; some modern taxonomists combine the two under the name Cetartiodactyla , while others opt to include cetaceans in the already-existing Artiodactyla. The roughly 270 land-based even-toed ungulate species include pigs, peccaries, hippopo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Two-toed Sloth
''Choloepus'' is a genus of xenarthran mammals of Central and South America within the monotypic family Choloepodidae, consisting of two-toed sloths, sometimes also called two-fingered sloths. The two species of ''Choloepus'' (which means "lame foot"), Linnaeus's two-toed sloth (''Choloepus didactylus'') and Hoffmann's two-toed sloth (''Choloepus hoffmanni''), were formerly believed on the basis of morphological studies to be the only surviving members of the sloth family Megalonychidae, but have now been shown by molecular results to be closest to extinct ground sloths of the family Mylodontidae. Extant species Evolution A study of retrovirus and mitochondrial DNA suggests that ''C. didactylus'' and ''C. hoffmani'' diverged 6 to 7 million years ago. Furthermore, based on cytochrome c oxidase subunit I sequences, a similar divergence date ( years ago) between the two populations of ''C. hofmanni'' separated by the Andes has been reported. Their ancestors evolved with mari ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypertragulidae
Hypertragulidae is an extinct family of artiodactyl ungulates that lived in North America, Europe, and Asia from the Eocene until the Miocene, living 46.2—13.6 million years ago, existing for about 33 million years. The Hypertragulidae are basal ruminants that resembled small deer or musk deer in life. However, neither deer, nor musk deer are considered to be closely related to the hypertragulids. Instead, the chevrotains are probably the closest living relatives to these ancient deer-like animals. Taxonomy Hypertragulidae was named by Cope (1879). This family was considered paraphyletic by Matthew (1908). It was assigned to Ruminantia by Matthew (1908) and Gregory (1910); to Pecora by Cook (1934); and to Traguloidea by Carroll (1988).H. J. Cook. 1934. New artiodactyls from the Oligocene and Lower Miocene of Nebraska. American Midland Naturalist 15(2):148-165 Morphology Hypertragulidae have tetradactyl front feet and didactyl rear feet, which is specific to this family and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quail
Quail is a collective name for several genera of mid-sized birds generally placed in the order Galliformes. The collective noun for a group of quail is a flock, covey, or bevy. Old World quail are placed in the family Phasianidae, and New World quail are placed in the family Odontophoridae. The species of buttonquail are named for their superficial resemblance to quail, and form the family Turnicidae in the order Charadriiformes. The king quail, an Old World quail, often is sold in the pet trade, and within this trade is commonly, though mistakenly, referred to as a "button quail". Many of the common larger species are farm-raised for table food or egg consumption, and are hunted on game farms or in the wild, where they may be released to supplement the wild population, or extend into areas outside their natural range. In 2007, 40 million quail were produced in the U.S. New World *Genus ''Callipepla'' **Scaled quail, (commonly called blue quail) ''Callipepla squamata'' **E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bustards
Bustards, including floricans and korhaans, are large, terrestrial birds living mainly in dry grassland areas and on the steppes of the Old World. They range in length from . They make up the family Otididae (, formerly known as Otidae). Bustards are omnivorous and opportunistic, eating leaves, buds, seeds, fruit, small vertebrates, and invertebrates.del Hoyo, J. Elliott, A. & Sargatal, J. (editors). (1996) ''Handbook of the Birds of the World. Volume 3: Hoatzin to Auks''. Lynx Edicions. There are 26 species currently recognised. Description Bustards are all fairly large with the two largest species, the kori bustard (''Ardeotis kori'') and the great bustard (''Otis tarda''), being frequently cited as the world's heaviest flying birds. In both the largest species, large males exceed a weight of , weigh around on average and can attain a total length of . The smallest species is the little brown bustard (''Eupodotis humilis''), which is around long and weighs around on average. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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