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Metaspriggiidae
''Metaspriggina'' is a genus of chordate initially known from two specimens in the Middle Cambrian Burgess Shale and 44 specimens found in 2012 at the Marble Canyon bed in Kootenay National Park. Whilst named after the Ediacaran organism ''Spriggina'', later work has shown the two to be unrelated. ''Metaspriggina'' is considered to represent a primitive chordate, possibly transitional between cephalochordates and the earliest vertebrates, albeit this has been questioned because it seems to possess most of the characteristics attributed to craniates. It lacked fins and it had a weakly developed cranium, but it did possess two well-developed upward-facing eyes with nostrils behind them. ''Metaspriggina'' also possessed a notochord, along with seven pairs of pharyngeal bars, possibly made of cartilage. Surprisingly they were not formed from a singular bone, but they were formed of multiple separate pairs of bones, along with first two of them that were enlarged compared to th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metaspriggina
''Metaspriggina'' is a genus of chordate initially known from two specimens in the Middle Cambrian Burgess Shale and 44 specimens found in 2012 at the Marble Canyon bed in Kootenay National Park. Whilst named after the Ediacaran organism ''Spriggina'', later work has shown the two to be unrelated. ''Metaspriggina'' is considered to represent a primitive chordate, possibly transitional between cephalochordates and the earliest vertebrates, albeit this has been questioned because it seems to possess most of the characteristics attributed to craniates. It lacked fins and it had a weakly developed cranium, but it did possess two well-developed upward-facing eyes with nostrils behind them. ''Metaspriggina'' also possessed a notochord, along with seven pairs of pharyngeal bars, possibly made of cartilage. Surprisingly they were not formed from a singular bone, but they were formed of multiple separate pairs of bones, along with first two of them that were enlarged compared to t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metaspriggina NT Small
''Metaspriggina'' is a genus of chordate initially known from two specimens in the Middle Cambrian Burgess Shale and 44 specimens found in 2012 at the Marble Canyon bed in Kootenay National Park. Whilst named after the Ediacaran organism ''Spriggina'', later work has shown the two to be unrelated. ''Metaspriggina'' is considered to represent a primitive chordate, possibly transitional between cephalochordates and the earliest vertebrates, albeit this has been questioned because it seems to possess most of the characteristics attributed to craniates. It lacked fins and it had a weakly developed cranium, but it did possess two well-developed upward-facing eyes with nostrils behind them. ''Metaspriggina'' also possessed a notochord, along with seven pairs of pharyngeal bars, possibly made of cartilage. Surprisingly they were not formed from a singular bone, but they were formed of multiple separate pairs of bones, along with first two of them that were enlarged compared t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chordate
A chordate () is an animal of the phylum Chordata (). All chordates possess, at some point during their larval or adult stages, five synapomorphies, or primary physical characteristics, that distinguish them from all the other taxa. These five synapomorphies include a notochord, dorsal hollow nerve cord, endostyle or thyroid, pharyngeal slits, and a post-anal tail. The name “chordate” comes from the first of these synapomorphies, the notochord, which plays a significant role in chordate structure and movement. Chordates are also Bilateral symmetry, bilaterally symmetric, have a coelom, possess a circulatory system, and exhibit Metameric, metameric segmentation. In addition to the morphological characteristics used to define chordates, analysis of genome sequences has identified two conserved signature indels (CSIs) in their proteins: cyclophilin-like protein and mitochondrial inner membrane protease ATP23, which are exclusively shared by all vertebrates, tunicates and cep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chordate
A chordate () is an animal of the phylum Chordata (). All chordates possess, at some point during their larval or adult stages, five synapomorphies, or primary physical characteristics, that distinguish them from all the other taxa. These five synapomorphies include a notochord, dorsal hollow nerve cord, endostyle or thyroid, pharyngeal slits, and a post-anal tail. The name “chordate” comes from the first of these synapomorphies, the notochord, which plays a significant role in chordate structure and movement. Chordates are also Bilateral symmetry, bilaterally symmetric, have a coelom, possess a circulatory system, and exhibit Metameric, metameric segmentation. In addition to the morphological characteristics used to define chordates, analysis of genome sequences has identified two conserved signature indels (CSIs) in their proteins: cyclophilin-like protein and mitochondrial inner membrane protease ATP23, which are exclusively shared by all vertebrates, tunicates and cep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nature (journal)
''Nature'' is a British weekly scientific journal founded and based in London, England. As a multidisciplinary publication, ''Nature'' features peer-reviewed research from a variety of academic disciplines, mainly in science and technology. It has core editorial offices across the United States, continental Europe, and Asia under the international scientific publishing company Springer Nature. ''Nature'' was one of the world's most cited scientific journals by the Science Edition of the 2019 ''Journal Citation Reports'' (with an ascribed impact factor of 42.778), making it one of the world's most-read and most prestigious academic journals. , it claimed an online readership of about three million unique readers per month. Founded in autumn 1869, ''Nature'' was first circulated by Norman Lockyer and Alexander Macmillan as a public forum for scientific innovations. The mid-20th century facilitated an editorial expansion for the journal; ''Nature'' redoubled its efforts in exp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gnathostomata
Gnathostomata (; from Greek: (') "jaw" + (') "mouth") are the jawed vertebrates. Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all living vertebrates, including humans. In addition to opposing jaws, living gnathostomes have true teeth (a characteristic which has subsequently been lost in some), paired appendages (pectoral and pelvic fins, arms, legs, wings, etc.), the elastomeric protein of elastin, and a horizontal semicircular canal of the inner ear, along with physiological and cellular anatomical characters such as the myelin sheaths of neurons, and an adaptive immune system that has the discrete lymphoid organs of spleen and thymus, and uses V(D)J recombination to create antigen recognition sites, rather than using genetic recombination in the variable lymphocyte receptor gene. It is now assumed that Gnathostomata evolved from ancestors that already possessed a pair of both pectoral and pelvic fins. Until recently these ancestors, know ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nostril
A nostril (or naris , plural ''nares'' ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation. Fish do not breathe through noses, but they do have two (but cyclostomes have merged into one) small holes used for smelling, which can also be referred to as nostrils. In humans, the nasal cycle is the normal ultradian cycle of each nostril's blood vessels becoming engorged in swelling, then shrinking. The nostrils are separated by the septum. The septum can sometimes be deviated, causing one nostril to appear larger than the other. With extreme damage to the septum and columella, the two nostrils are no longer separated and form a single larger external opening. Like other tetrapods, humans have two external nostrils (anterior nares) and two additi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Notochord
In anatomy, the notochord is a flexible rod which is similar in structure to the stiffer cartilage. If a species has a notochord at any stage of its life cycle (along with 4 other features), it is, by definition, a chordate. The notochord consists of inner, vacuolated cells covered by fibrous and elastic sheaths, lies along the anteroposterior axis (''front to back''), is usually closer to the dorsal than the ventral surface of the embryo, and is composed of cells derived from the mesoderm. The most commonly cited functions of the notochord are: as a midline tissue that provides directional signals to surrounding tissue during development, as a skeletal (structural) element, and as a vertebral precursor. In lancelets the notochord persists throughout life as the main structural support of the body. In tunicates the notochord is present only in the larval stage, being completely absent in the adult animal. In these invertebrate chordates, the notochord is not vacuolated. In all ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cartilage
Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck and the bronchial tubes, and the intervertebral discs. In other taxa, such as chondrichthyans, but also in cyclostomes, it may constitute a much greater proportion of the skeleton. It is not as hard and rigid as bone, but it is much stiffer and much less flexible than muscle. The matrix of cartilage is made up of glycosaminoglycans, proteoglycans, collagen fibers and, sometimes, elastin. Because of its rigidity, cartilage often serves the purpose of holding tubes open in the body. Examples include the rings of the trachea, such as the cricoid cartilage and carina. Cartilage is composed of specialized cells called chondrocytes that produce a large amount of collagenous extracellular matrix, abundant ground substance that is rich in pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taylor & Francis
Taylor & Francis Group is an international company originating in England that publishes books and academic journals. Its parts include Taylor & Francis, Routledge, F1000 (publisher), F1000 Research or Dovepress. It is a division of Informa, Informa plc, a United Kingdom–based publisher and conference company. Overview The company was founded in 1852 when William Francis (chemist), William Francis joined Richard Taylor (editor), Richard Taylor in his publishing business. Taylor had founded his company in 1798. Their subjects covered agriculture, chemistry, education, engineering, geography, law, mathematics, medicine, and social sciences. Francis's son, Richard Taunton Francis (1883–1930), was sole partner in the firm from 1917 to 1930. In 1965, Taylor & Francis launched Wykeham Publications and began book publishing. T&F acquired Hemisphere Publishing in 1988, and the company was renamed Taylor & Francis Group to reflect the growing number of Imprint (trade name), imp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seabed
The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of the ocean is very deep, where the seabed is known as the abyssal plain. Seafloor spreading creates mid-ocean ridges along the center line of major ocean basins, where the seabed is slightly shallower than the surrounding abyssal plain. From the abyssal plain, the seabed slopes upward toward the continents and becomes, in order from deep to shallow, the continental rise, slope, and shelf. The depth within the seabed itself, such as the depth down through a sediment core, is known as the “depth below seafloor.” The ecological environment of the seabed and the deepest waters are collectively known, as a habitat for creatures, as the “benthos.” Most of the seabed throughout the world's oceans is covered in layers of marine sediments. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Craniate
A craniate is a member of the Craniata (sometimes called the Craniota), a proposed clade of chordate animals with a skull of hard bone or cartilage. Living representatives are the Myxini (hagfishes), Hyperoartia (including lampreys), and the much more numerous Gnathostomata (jawed vertebrates).Campbell & Reece 2005 p. 676 Formerly distinct from vertebrates by including hagfish, molecular and anatomical research in the 21st century has led to the reinclusion of hagfish as vertebrates, making living craniates synonymous with living vertebrates. The clade was conceived largely on the basis of the Hyperoartia (lampreys and kin) being more closely related to the Gnathostomata (jawed vertebrates) than the Myxini (hagfishes). This, combined with an apparent lack of vertebral elements within the Myxini, suggested that the Myxini were descended from a more ancient lineage than the vertebrates, and that the skull developed before the vertebral column. The clade was thus composed of the Myx ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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