Eutheria (Greek Greek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical ancient Greek literature and the New Testament of: "true beasts") are a group of mammals Mammals are a class of vertebrate, air-breathing animals whose females are characterized by the possession of mammary glands while both males and females are characterized by hair and/or fur, three middle ear bones used in hearing, and a neocortex region in the brain. Some mammals have sweat glands, but most do not consisting of placental The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. Placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and lizards with varying levels of development up to mammals plus all extinct mammals Mammals are a class of vertebrate, air-breathing animals whose females are characterized by the possession of mammary glands while both males and females are characterized by hair and/or fur, three middle ear bones used in hearing, and a neocortex region in the brain. Some mammals have sweat glands, but most do not that are more closely related to living placentals (such as humans) than to living marsupials Marsupials are an infraclass of mammals, characterized by a distinctive pouch , in which females carry their young through early infancy. In modern times, they are well-known for being the dominant group of mammals in Australia, though there are also a number of species found in the Americas, as well as on the island of New Guinea (such as kangaroos). They are distinguished from non-eutherians by various features of the feet, ankles, jaws and teeth. One of the major differences between placental and non-placental eutherians is that placentals lack epipubic bones In modern marsupials the epipubic bones are often called "marsupial bones" because they support the mother's pouch . But their presence on other groups of mammals indicates that this was not their original function, which some researchers think was to assist locomotion by supporting some of the muscles that flex the thigh, which are present in all other fossil Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers (strata) is known as the fossil record. The study of fossils across geological time, how and living mammals.
The earliest known fossil eutherian, Eomaia Eomaia is an extinct fossil mammal, discovered in rocks that were found in the Yixian Formation, Liaoning Province, China, and dated to the Barremian Age of the Lower Cretaceous about 125 million years ago. The fossil is 10 centimetres (3.9 in) in length and virtually complete. An estimate of the body weight is between 20–25 grams (0.71–0.88 was found in Asia and is dated to the Early Cretaceous The Cretaceous , Latin for "chalky", usually abbreviated K for its German translation Kreide (chalk), is a geologic period and system from circa 145.5 ± 4 to 65.5 ± 0.3 million years (Ma) ago. In the geologic timescale, the Cretaceous follows on the Jurassic Period and is followed by the Paleogene Period of the Cenozoic Era. It is the period, about 125 million years ago.
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Definition
Eutherians are a group of mammals consisting of placental mammals plus all extinct mammals Mammals are a class of vertebrate, air-breathing animals whose females are characterized by the possession of mammary glands while both males and females are characterized by hair and/or fur, three middle ear bones used in hearing, and a neocortex region in the brain. Some mammals have sweat glands, but most do not that are more closely related to living placentals (such as humans) than to living marsupials Marsupials are an infraclass of mammals, characterized by a distinctive pouch , in which females carry their young through early infancy. In modern times, they are well-known for being the dominant group of mammals in Australia, though there are also a number of species found in the Americas, as well as on the island of New Guinea (such as kangaroos).[2]
There are no living non-placental eutherians, and so knowledge of their synapomorphies In cladistics, a synapomorphy or synapomorphic character is a trait that is shared by two or more taxa and their most recent common ancestor, whose ancestor in turn does not possess the trait. A synapomorphy is thus an apomorphy visible in multiple taxa, where the trait in question originates in their last common ancestor. The word " ("defining features") is entirely based on a few fossils Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers (strata) is known as the fossil record. The study of fossils across geological time, how – which means the reproductive Reproduction is the biological process by which new "offspring" individual organisms are produced from their "parents". Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction. The known methods of reproduction are broadly grouped into two main types: sexual and features that distinguish modern placentals from other mammals cannot be used in defining the eutheria. The features of eutheria that distinguish them from metatherians Metatheria is a grouping within the animal class Mammalia. First proposed by Thomas Henry Huxley in 1880, it is nearly synonymous with the earlier taxon Marsupialia though it is slightly wider since it also contains the nearest fossil relatives of marsupial mammals, a group that includes modern marsupials, are:
- an enlarged malleolus The lower extremity of the fibula, also called the distal extremity or external malleolus, is of a pyramidal form and somewhat flattened from side to side; it descends to a lower level than the medial malleolus ("little hammer") at the bottom of the tibia The tibia, shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones. The tibia is named for the greek aulos flute, also known as a tibia. It is commonly recognised as the strongest weight bearing bone in the body, the larger of the two shin bones.[2]
- the joint between the first metatarsal The metatarsus or metatarsal bones are a group of five long bones in the foot located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the medial side : the first, second, third, fourth, and fifth metatarsal. The metatarsals are analogous to the bone and the entocuneiform bone in the foot is offset further back than the joint between the second metatarsal and mesocuneiform bones – in metatherians these joints are level with each other.[2]
- various features of jaws and teeth.[2]
Reproductive features are also of no use in identifying fossil placental mammals, which are distinguished from other eutherians by:
- the presence of a malleolus at the bottom of the fibula The fibula or calf bone is a bone located on the lateral side of the tibia, with which it is connected above and below. It is the smaller of the two bones, and, in proportion to its length, the most slender of all the long bones. Its upper extremity is small, placed toward the back of the head of the tibia, below the level of the knee-joint, and, the smaller of the two shin bones.[2]
- a complete mortise and tenon Simple and strong, the mortise and tenon joint has been used for thousands of years by woodworkers around the world to join pieces of wood, usually when the pieces are at an angle close to 90°. Although there are many variations on the theme, the basic idea is that the end of one of the members is inserted into a hole cut in the other member. The upper ankle joint, where the rearmost bones of the foot fit into a socket formed by the ends of the tibia and fibula.[2]
- a wide opening at the bottom of the pelvis In human anatomy, the pelvis is the part of the trunk inferioposterior (below-behind) to the abdomen in the transition area between the trunk (torso) and the lower limbs (legs). The term is used to denote several structures:, which allows the birth of large, well-developed offspring. Marsupials have and non-placental eutherians had a narrower opening that allows only small, immature offspring to pass through.[3]
- the absence of epipubic bones In modern marsupials the epipubic bones are often called "marsupial bones" because they support the mother's pouch . But their presence on other groups of mammals indicates that this was not their original function, which some researchers think was to assist locomotion by supporting some of the muscles that flex the thigh extending forwards from the pelvis, which are not found in any placental, but are found in all other mammals – non-placental eutherians, marsupials, monotremes Monotremes are mammals that lay eggs (Prototheria) instead of giving birth to live young like marsupials (Metatheria) and placental mammals (Eutheria) and mammaliformes Mammaliaformes is a clade that contains the mammals and their closest extinct relatives. Phylogenetically it is defined as a clade including the most recent common ancestor of Sinoconodon, morganuconodonts, docodonts, Monotremata, Marsupialia, Placentalia, extinct members of this clade, and all of its descendants. The precise phylogeny is disputed – and even in the cynodont therapsids Therapsida is a group of synapsids that includes mammals and their immediate evolutionary ancestors. Other than the mammals, all lineages of the therapsids are extinct, with the last known non-mammalian therapsids dying out in the Early Cretaceous period . The first fossil attributed to therapsida is believed to be Tetraceratops insignis (Lower that are closest to mammals. Their function is to stiffen the body during locomotion.[4] This stiffening would be harmful in pregnant placentals, whose abdomens need to expand.[5]
Subgroups
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These are the subgroups of extant members of Eutheria:
- Boreoeutheria Boreoeutheria (Gk: βόρειο North + θεριό Beast) is a clade (magnorder) of placental mammals that is composed of the sister taxa Laurasiatheria and Euarchontoglires (Supraprimates). It is now well supported by DNA sequence analyses as well as retrotransposon presence/absence data. All male members of the clade share the distinction of, e.g. humans Humans are a species of animal known taxonomically as Homo sapiens , and are the only extant member of the Homo genus of bipedal primates in Hominidae, the great ape family. However, in some cases "human" is used to refer to any member of the genus Homo, badgers Badgers, occasionally referred to as brocks, are short-legged, heavy-set omnivores in the weasel biologicalfamily, Mustelidae. There are eight species of badger, in three subfamilies : Melinae (badgers of Europe and Asia), Mellivorinae (the Ratel or honey badger), and Taxideinae (the American badger). The Asiatic stink badgers of the genus Mydaus, rabbits, guinea pigs The guinea pig , also commonly called the cavy, is a species of rodent belonging to the family Caviidae and the genus Cavia. Despite their common name, these animals are not pigs, nor do they come from Guinea. They originated in the Andes, and studies based on biochemistry and hybridization suggest they are domesticated descendants of a closely, dogs The dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The domestic dog has been one of the most widely kept working and companion animals in human history, dolphins Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in seventeen genera. They vary in size from 1.2 m and 40 kg (90 lb) (Maui's Dolphin), up to 9.5 m (30 ft) and 10 tonnes (9.8 LT; 11 ST) (the Orca or Killer Whale). They are found worldwide, mostly in the shallower seas of the
- Euarchontoglires Euarchontoglires is a clade of mammals, the living members of which include rodents and primates (including humans), e.g. monkeys, rats, hares
- Laurasiatheria Laurasiatheria is a large group of placental mammals. It includes bats, whales, most hoofed mammals, and carnivorans, among other mammals, e.g. cattle, whales, bats, cats
- Atlantogenata Atlantogenata is a proposed clade of mammals containing the cohorts or super-orders Xenarthra and Afrotheria. These groups originated and radiated in the South American and African continents, presumably in the Cretaceous. Together with Boreoeutheria it makes up Eutheria, e.g. sloths The living sloths comprise six species of medium-sized mammals belonging to the families Megalonychidae and Bradypodidae, part of the order Pilosa. They are arboreal residents of the rainforests of Central and South America. The sloth's taxonomic suborder is Folivora, while some call it Phyllophaga. Both names mean "leaf-eaters"; the, hyraxes, aardvarks, tenrecs, armadillos Armadillos are small placental mammals, known for having a leathery armor shell. The Dasypodidae are the only surviving family in the order Cingulata, part of the superorder Xenarthra along with the anteaters and sloths. The word armadillo is Spanish for "little armored one", anteaters
- Xenarthra The superorder Xenarthra is a group of placental mammals , extant today only in the Americas. The origins of the order can be traced back as far as the early Tertiary (about 60 million years ago, shortly after the Mesozoic era). The presence of these animals in Central and North America is explained by the Great American Interchange, e.g. armadillos, anteaters
- Afrotheria Afrotheria is a clade of mammals, the living members of which include golden moles, sengis , tenrecs, aardvarks, hyraxes, elephants and sea cows, e.g. elephants Elephants are large land mammals in two genera of the family Elephantidae: Elephas and Loxodonta. Three species of elephant are living today: the African Bush Elephant, the African Forest Elephant and the Asian Elephant . All other species and genera of Elephantidae are extinct, some since the last ice age: dwarf forms of mammoths may have, manatees Manatees are large, fully aquatic, mostly herbivorous marine mammals sometimes known as sea cows. They are noted for their friendly nature, their large size (up to 3.6 metres (12 ft)), and paddle-like flippers. The name manatí comes from the Taíno, a pre-Columbian people of the Caribbean, meaning "breast"
These groups together make up the crown group A crown group is the smallest monophyletic group, or "clade", to contain the last common ancestor of all extant members, and all of that ancestor's descendants. Extinct organisms can still be part of a crown group: for instance, the extinct dodo is still descended from the last common ancestor of all living birds, so falls within the Placentalia (placental mammals). Eutheria also includes now extinct lineages that lie outside of Placentalia (see below).[10]
Evolutionary history
| The earliest known eutherian species is the extinct non-placental Eomaia scansoria from the Lower Cretaceous of China, dated to about 125 million years ago. Some of its fossils show thick fur. Montanalestes was found in North America, while all other non-placental eutherian fossils have been found in Asia. The earliest known placental fossils have also been found in Asia.[2] | Millions of years ago — = Placentals — = Other eutheria Origin of eutheria = Asian fossils = N American fossils = Period when placental classes diverged according to molecular phylogenetics estimates Murtoilestes Prokennalestes Eomaia Montanalestes Ukhaatherium Asioryctes Kennalestes Zalambdalestes Daulestes Aspanestes Eoungulatum Protungulatum Gypsonictops Cimolestes Fossil record of Cretaceous eutheria[2] |
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Notes and references
| Wikispecies has information related to: Eutheria |
| Wikisource has the text of the 1911 Encyclopædia Britannica article Monodelphia. |
- ^ "Eutheria phylogeny". Mikko's Phylogeny Archive. http://www.helsinki.fi/~mhaaramo/metazoa/deuterostoma/chordata/synapsida/eutheria/eutheria_index.html. Retrieved 2008-07-24.
- ^ a b c d e f g h i Ji, Q., Luo, Z-X., Yuan, C-X.,Wible, J.R., Zhang, J-P.,and Georgi, J.A. (April 2002). "The earliest known eutherian mammal". Nature 416 (6883): 816–822. doi:10.1038/416816a. PMID 11976675. http://www.nature.com/nature/journal/v416/n6883/full/416816a.html. Retrieved 2008-09-24.
- ^ Weil, A. (April 2002). "Mammalian evolution: Upwards and onwards". Nature 416 (6883): 798–799. doi:10.1038/416798a. PMID 11976661. http://www.nature.com/nature/journal/v416/n6883/full/416798a.html. Retrieved 2008-09-24.
- ^ Reilly, S.M., and White, T.D. (January 2003). "Hypaxial Motor Patterns and the Function of Epipubic Bones in Primitive Mammals". Science 299 (5605): 400–402. doi:10.1126/science.1074905. PMID 12532019. http://www.sciencemag.org/cgi/content/full/299/5605/400. Retrieved 2008-09-24.
- ^ Novacek, M.J., Rougier, G.W, Wible, J.R., McKenna, M.C, Dashzeveg, D.,and Horovitz, I. (October 1997). "Epipubic bones in eutherian mammals from the Late Cretaceous of Mongolia". Nature 389 (6650): 483–486. doi:10.1038/39020. PMID 9333234. http://www.nature.com/nature/journal/v389/n6650/full/389483a0.html. Retrieved 2008-09-24.
- ^ Wildman DE, Uddin M, Opazo JC, et al (2007). "Genomics, biogeography, and the diversification of placental mammals". Proc. Natl. Acad. Sci. U.S.A. 104 (36): 14395–400. doi:10.1073/pnas.0704342104. PMID 17728403. PMC 1958817. http://www.pnas.org/content/104/36/14395.full.
- ^ Murphy WJ, Pringle TH, Crider TA, Springer MS, Miller W (2007). "Using genomic data to unravel the root of the placental mammal phylogeny". Genome Res. 17 (4): 413–21. doi:10.1101/gr.5918807. PMID 17322288. PMC 1832088. http://genome.cshlp.org/content/17/4/413.long.
- ^ Schneider A, Cannarozzi GM (2009). "Support Patterns from Different Outgroups Provide a Strong Phylogenetic Signal". Mol. Biol. Evol. 26 (6): 1259–72. doi:10.1093/molbev/msp034. PMID 19240194.
- ^ Churakov G, Kriegs JO, Baertsch R, Zemann A, Brosius J, Schmitz J (2009). "Mosaic Retroposon Insertion Patterns in Placental Mammals". Genome Res. 19 (5): 868–75. doi:10.1101/gr.090647.108. PMID 19261842.
- ^ Archibald JD, Averianov AO, Ekdale EG (November 2001). "Late Cretaceous relatives of rabbits, rodents, and other extant eutherian mammals". Nature 414 (6859): 62–5. doi:10.1038/35102048. PMID 11689942.
References
- Goloboff, P.A.; Catalano, S.A.; Mirande, J.M.; Szumik, C.A.; Arias, J.S.; Källersjö, M & Farris, J.S. 2009. Phylogenetic analysis of 73 060 taxa corroborates major eukaryotic groups. Cladistics 25 (3): 211-230
Categories: Mammals
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... Eutheria Ordine: Carnivora _ famiglia: Canidae Sottofamiglia: Caninae Genere: Canis Specie: Canis lupus (secondo Linnaeus: Canis lupus lupus); ...
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Sun, 31 Jan 2010 07:19:36 GM
More information about . Eutheria. can be found here.
Q. Kingdom: Animalia Phylum: chordata Subphylum: vertebrata superclass: tetrapoda class: mammalia subclass: Theria Infraclass: Eutheria Cohort: Unguiculata Order: Primata Suborder: Anthropoidea Superfamily: Hominoidae Family: Hominiae Genus: Homo Species: Sapiens Does this classification represent reality in the sense that the world is ordered this way independent of our articulation of the various hierarchical levels? In other words, was this scheme (or something like it with different names and perhaps different "levels") "out there waiting" to be discovered? Or does this classification construct reality in the sense that world is only ordered in this way because Linnaeus (and we after him) imposed this system on an otherwise… [cont.]
Asked by dr.cpereira - Tue Feb 2 11:53:07 2010 - - 1 Answers - 0 Comments
A. The Linnaean classification system is very useful in considering relationships between living organisms, but it is an abstraction of reality, representing one description only of a complex being. Since individual differentiation is present even at species level, such a system can never do more than represent an approximation of reality.
Answered by Mustafa Kohan - Tue Feb 2 13:48:18 2010
