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Archaeodobenus
''Archaeodobenus'' is an extinct genus of pinniped that lived during the Late Miocene of what is now Japan. It belonged to the Odobenidae family, which is today only represented by the walrus, but was much more diverse in the past, containing at least 16 genera. Unlike the modern walrus, ''Archaeodobenus'' did not have tusks but instead had canines of moderate size, and looked more like a sea lion. Discovery The first known specimen was collected in 1977 from the Ichibangawa Formation in Tobetsu Town on the island of Hokkaido. The specimen consists of a partial skull, vertebrae, and limb bones, and was made the holotype specimen of the new genus and species ''A. akamatsui'' by the Japanese palaeontologists Yoshihiro Tanaka and Naoki Kohno in 2015. The generic name consists of ''archaio-'', the Greek word for ancient, and the generic name of the walrus, ''Odobenus''; in full, "ancient walrus." The specific name honors Morio Akamatsu, a curator of the Hokkaido Museum. The ho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Pinniped
Pinnipeds (pronounced ), commonly known as seals, are a widely range (biology), distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammal, marine mammals. They comprise the extant taxon, extant family (biology), families Odobenidae (whose only living member is the walrus), Otariidae (the eared seals: sea lions and fur seals), and Phocidae (the earless seals, or true seals). There are 34 extant species of pinnipeds, and more than 50 extinct species have been described from fossils. While seals were historically thought to have descended from two ancestral lines, molecular phylogenetics, molecular evidence supports them as a monophyletic lineage (descended from one ancestral line). Pinnipeds belong to the order Carnivora; their closest living relatives are Musteloidea, musteloids (Mustelidae, weasels, Procyonidae, raccoons, skunks, and red pandas), having diverged about 50 million years ago. Seals range in size from the and Baikal sea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Odobenidae
Odobenidae is a family of pinnipeds. The only living species is the walrus (''Odobenus rosmarus''). In the past, however, the group was much more diverse, and includes more than a dozen fossil genera. Taxonomy All genera, except ''Odobenus'', are extinct. *†''Archaeodobenus'' *†''Prototaria'' *†''Proneotherium'' *†''Nanodobenus'' *†''Neotherium'' *†''Imagotaria'' *†'' Kamtschatarctos'' *†''Pelagiarctos'' *†'' Pontolis'' *†'' Pseudotaria'' *†''Titanotaria'' *Clade Neodobenia **†'' Gomphotaria'' **Subfamily Dusignathinae ***†'' Dusignathus'' **Subfamily Odobeninae ***†''Aivukus'' ***†'' Ontocetus'' ***†'' Pliopedia'' ***†'' Protodobenus'' ***†'' Valenictus'' ***''Odobenus The walrus (''Odobenus rosmarus'') is a large flippered marine mammal with a discontinuous distribution about the North Pole in the Arctic Ocean and subarctic seas of the Northern Hemisphere. The walrus is the only living species in the fa ...'' In re-analyzing ''Pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Holotype
A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several examples, but explicitly designated as the holotype. Under the International Code of Zoological Nomenclature (ICZN), a holotype is one of several kinds of name-bearing types. In the International Code of Nomenclature for algae, fungi, and plants (ICN) and ICZN, the definitions of types are similar in intent but not identical in terminology or underlying concept. For example, the holotype for the butterfly '' Plebejus idas longinus'' is a preserved specimen of that subspecies, held by the Museum of Comparative Zoology at Harvard University. In botany, an isotype is a duplicate of the holotype, where holotype and isotypes are often pieces from the same individual plant or samples from the same gathering. A holotype is not necessaril ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Prehistoric Carnivoran Genera
Prehistory, also known as pre-literary history, is the period of human history between the use of the first stone tools by hominins 3.3 million years ago and the beginning of recorded history with the invention of writing systems. The use of symbols, marks, and images appears very early among humans, but the earliest known writing systems appeared 5000 years ago. It took thousands of years for writing systems to be widely adopted, with writing spreading to almost all cultures by the 19th century. The end of prehistory therefore came at very different times in different places, and the term is less often used in discussing societies where prehistory ended relatively recently. In the early Bronze Age, Sumer in Mesopotamia, the Indus Valley Civilisation, and ancient Egypt were the first civilizations to develop their own scripts and to keep historical records, with their neighbors following. Most other civilizations reached the end of prehistory during the following Iron Age. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Miocene Pinnipeds
The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent" because it has 18% fewer modern marine invertebrates than the Pliocene has. The Miocene is preceded by the Oligocene and is followed by the Pliocene. As Earth went from the Oligocene through the Miocene and into the Pliocene, the climate slowly cooled towards a series of ice ages. The Miocene boundaries are not marked by a single distinct global event but consist rather of regionally defined boundaries between the warmer Oligocene and the cooler Pliocene Epoch. During the Early Miocene, the Arabian Peninsula collided with Eurasia, severing the connection between the Mediterranean and Indian Ocean, and allowing a faunal interchange to occur between Eurasia and Africa, including the dispersal of proboscideans into Eurasia. During the late ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Basal (phylogenetics)
In phylogenetics, basal is the direction of the ''base'' (or root) of a rooted phylogenetic tree or cladogram. The term may be more strictly applied only to nodes adjacent to the root, or more loosely applied to nodes regarded as being close to the root. Note that extant taxa that lie on branches connecting directly to the root are not more closely related to the root than any other extant taxa. While there must always be two or more equally "basal" clades sprouting from the root of every cladogram, those clades may differ widely in taxonomic rank, species diversity, or both. If ''C'' is a basal clade within ''D'' that has the lowest rank of all basal clades within ''D'', ''C'' may be described as ''the'' basal taxon of that rank within ''D''. The concept of a 'key innovation' implies some degree of correlation between evolutionary innovation and diversification. However, such a correlation does not make a given case predicable, so ancestral characters should not be imputed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Pontolis
''Pontolis'' is an extinct genus of large walrus. It contained three species, ''P. magnus, P. barroni,'' and ''P. kohnoi''. Like all pinnipeds, ''Pontolis'' was a heavily built amphibious carnivore. ''Pontolis'' lived along the Pacific coast of North America along what is now the western coasts of California and Oregon between 11.608 and 5.332 million years ago, during the Miocene and Pliocene. Description The skull of ''Pontolis'' is long, surpassing skulls of any other prehistoric pinnipeds and twice as big as the skulls of modern male walruses. This giant species was much larger than modern walrus, though like many other extinct walrus species, its upper canines did not develop into long tusks like those of the modern walrus. ''Pontolis'' reached more than in body length, rivaling the extant southern elephant seal as the largest pinniped and member of the order Carnivora Carnivora is a monophyletic order of placental mammals consisting of the most recent common ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Imagotaria
''Imagotaria'' is an extinct monotypic genus of walrus with the sole species ''Imagotaria downsi''. Fossils of ''Imagotaria'' are known from the early late Miocene of California (c. 10-12 million years ago). Description The long pinniped more closely resembled in its overall shape a sea lion rather than a walrus. Unlike the extant walrus (''Odobenus rosmarus''), ''Imagotaria'' did not possess elongate, ever-growing tusks, but instead bore enlarged canines (with respect to other pinnipeds). ''Imagotaria'' is an example of a primitive walrus that does not grossly appear similar to a modern walrus. However, the walrus family (the Odobenidae) is a more inclusive group, that includes walruses without tusks (e.g. ''Imagotaria''), walruses with upper and lower tusks (the subfamily Dusignathinae), and walruses with upper tusks like the extant walrus (subfamily Odobeninae, tribe Odobenini). It is possible to classify these pinnipeds as walruses because they share many other skull fea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Marine Transgression
A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, which results in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling with water or decreasing in capacity. Transgressions and regressions may be caused by tectonic events such as orogenies, severe climate change such as ice ages or isostatic adjustments following removal of ice or sediment load. During the Cretaceous, seafloor spreading created a relatively shallow Atlantic basin at the expense of deeper Pacific basin. That reduced the world's ocean basin capacity and caused a rise in sea level worldwide. As a result of the sea level rise, the oceans transgressed completely across the central portion of North America and created the Western Interior Seaway from the Gulf of Mexico to the Arctic Ocean. The opposite of transgression is regression in which the sea level falls relative to the land and e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |