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Acanthostega Gunnari
''Acanthostega'', from Ancient Greek ἄκανθα (''ákantha''), meaning "spine", and στέγη (''stégē''), meaning "roof", is an extinct genus of stem-tetrapod, among the first vertebrate animals to have recognizable limbs. It appeared in the late Devonian period ( Famennian age) about 365 million years ago, and was anatomically intermediate between lobe-finned fishes and those that were able to come onto land. Discovery The fossilized remains are generally well preserved, with the famous fossil by which the significance of this species was discovered being found by Jennifer A. Clack in East Greenland in 1987, though fragments of the skull had been discovered in 1933 by Gunnar Säve-Söderbergh and Erik Jarvik. Description The ''Acanthostega'' had eight digits on each hand (the number of digits on the feet is unclear) linked by webbing. It lacked wrists, and was generally poorly adapted for walking on land. It also had a remarkably fish-like shoulder and forel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Late Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era during the Phanerozoic eon, spanning 60.3 million years from the end of the preceding Silurian period at million years ago ( Ma), to the beginning of the succeeding Carboniferous period at Ma. It is the fourth period of both the Paleozoic and the Phanerozoic. It is named after Devon, South West England, where rocks from this period were first studied. The first significant evolutionary radiation of life on land occurred during the Devonian, as free- sporing land plants (pteridophytes) began to spread across dry land, forming extensive coal forests which covered the continents. By the middle of the Devonian, several groups of vascular plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants ( pteridospermatophytes) appeared. This rapid evolution and colonization process, which had begun during the Silurian, is known as the Silurian-Devonian Terrestrial Rev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Simplified Phylogeny Spanning The Fish–tetrapod Transition
Simplification, Simplify, or Simplified may refer to: Mathematics Simplification is the process of replacing a mathematical expression by an equivalent one that is simpler (usually shorter), according to a well-founded ordering. Examples include: * Simplification of algebraic expressions, in computer algebra * Simplification of boolean expressions i.e. logic optimization * Simplification by conjunction elimination in inference in logic yields a simpler, but generally non-equivalent formula * Simplification of fractions Science * Approximations simplify a more detailed or difficult to use process or model Linguistics * Simplification of Chinese characters * Simplified English (other) * Text simplification Music * ''Simplify'', a 1999 album by Ryan Shupe & the RubberBand * Simplified (band), a 2002 rock band from Charlotte, North Carolina * ''Simplified'' (album), a 2005 album by Simply Red * "Simplify", a 2008 song by Sanguine * "Simplify", a 2018 song by Young the G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coelacanth
Coelacanths ( ) are an ancient group of lobe-finned fish (Sarcopterygii) in the class Actinistia. As sarcopterygians, they are more closely related to lungfish and tetrapods (the terrestrial vertebrates including living amphibians, reptiles, birds and mammals) than to ray-finned fish. The name coelacanth originates from the Permian genus '' Coelacanthus'', which was the first scientifically named genus of coelacanths (in 1839), becoming the type genus of Coelacanthiformes as other species were discovered and named. Well-represented in freshwater and marine deposits from as early as the Devonian period (more than 410million years ago), they were thought to have become extinct in the Late Cretaceous, around 66million years ago. The first living species, ''Latimeria chalumnae'', the West Indian Ocean coelacanth, was described from specimens fished off the coast of South Africa from 1938 onward; they are now also known to inhabit the seas around the Comoro Islands off the eas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stegocephalia
Stegocephali (often spelled Stegocephalia, from Greek , lit. "roofed head") is a clade of vertebrate animals containing all fully limbed tetrapodomorphs. It is equivalent to a broad definition of the superclass Tetrapoda: under this broad definition, the term "tetrapod" applies to any animal descended from the first vertebrate with four limbs each with digits in the extremity ( pentadactyly), rather than fins of their sarcopterygian relatives. Stegocephalians include both the modern lineage of limbed vertebrates (the crown group tetrapods, including modern amphibians, reptiles, birds and mammals) as well as a portion of the stem group, the earliest limbed tetrapodomorphs such as '' Ichthyostega'' and '' Acanthostega'', which evolved in the Devonian period long before the origin of the crown group. Many paleontologists prefer a stricter definition of Tetrapoda which applies solely to the crown group, excluding earlier types of limbed tetrapodomorphs. Stegocephali was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Panderichthys
''Panderichthys'' is a genus of extinction, extinct Sarcopterygii, sarcopterygian (lobe-finned fish) from the late Devonian period, about 380 Myr, Mya. ''Panderichthys'', which was recovered from Frasnian (early Late Devonian) deposits in Latvia, is represented by two species. ''P. stolbovi'' is known only from some snout fragments and an incomplete lower jaw. ''P. rhombolepis'' is known from several more complete specimens. Although it probably belongs to a sister group of the earliest tetrapods, ''Panderichthys'' exhibits a range of features transitional between Tristichopteridae, tristichopterid lobe-fin fishes (e.g., ''Eusthenopteron'') and early tetrapods. It is named after the German-Baltic paleontologist Christian Heinrich Pander. Possible tetrapod tracks dating back to before the appearance of ''Panderichthys'' in the fossil record were reported in 2010, which suggests that ''Panderichthys'' is not a direct ancestor of tetrapods, but nonetheless shows the traits that evolve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eusthenopteron
''Eusthenopteron'' (from 'stout', and 'wing' or 'fin') is an extinct genus of prehistoric marine lobe-finned fish known from several species that lived during the Late Devonian period, about 385 million years ago. It has attained an iconic status from its close relationship to tetrapods. Early depictions of animals of this genus show them emerging onto land, but paleontologists now think that ''Eusthenopteron'' species were strictly aquatic animals, though this is not completely known.M. Laurin, F. J. Meunier, D. Germain, and M. Lemoine 2007A microanatomical and histological study of the paired fin skeleton of the Devonian sarcopterygian ''Eusthenopteron foordi'' ''Journal of Paleontology'' 81: 143–153. The genus was first described by J. F. Whiteaves in 1881, as part of a large collection of fishes from Miguasha, Quebec, Canada. Some 2,000 ''Eusthenopteron'' specimens have been collected from Miguasha, one of which was the object of intensely detailed study and severa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sarcopterygii
Sarcopterygii (; )—sometimes considered synonymous with Crossopterygii ()—is a clade (traditionally a class (biology), class or subclass) of vertebrate animals which includes a group of bony fish commonly referred to as lobe-finned fish. These vertebrates are characterised by prominent muscular limb buds (lobes) within their fish fin, fins, which are supported by articulated appendicular skeletons. This is in contrast to the other clade of bony fish, the Actinopterygii, which have only skin-covered lepidotrichia, bony spines supporting the fins. The tetrapods, a mostly terrestrial animal, terrestrial clade of vertebrates, are now recognized as having evolved from sarcopterygian ancestors and are most closely related to lungfishes. Their paired pectoral fins, pectoral and pelvic fins evolved into limb (anatomy), limbs, and their lung bud, foregut diverticulum eventually evolved into air-breathing lungs. Cladistics, Cladistically, this would make the tetrapods a subgroup within ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pelagic Zone
The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the surface of the sea and the bottom. Conditions in the water column change with depth: pressure increases; temperature and light decrease; salinity, oxygen, micronutrients (such as iron, magnesium and calcium) all change. In a manner analogous to stratification in the Earth's atmosphere, the water column can be divided vertically into up to five different layers (illustrated in the diagram), with the number of layers depending on the depth of the water. Marine life is affected by bathymetry (underwater topography) such as the seafloor, shoreline, or a submarine seamount, as well as by proximity to the boundary between the ocean and the atmosphere at the ocean surface, which brings light for photosynthesis, predation from above, and wind sti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vertebrate
Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebrata with some 65,000 species, by far the largest ranked grouping in the phylum Chordata. The vertebrates include mammals, birds, amphibians, and various classes of fish and reptiles. The fish include the jawless Agnatha, and the jawed Gnathostomata. The jawed fish include both the Chondrichthyes, cartilaginous fish and the Osteichthyes, bony fish. Bony fish include the Sarcopterygii, lobe-finned fish, which gave rise to the tetrapods, the animals with four limbs. Despite their success, vertebrates still only make up less than five percent of all described animal species. The first vertebrates appeared in the Cambrian explosion some 518 million years ago. Jawed vertebrates evolved in the Ordovician, followed by bony fishes in the Devonian. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ichthyostega
''Ichthyostega'', from Ancient Greek ἰχθύς (''ikthús''), meaning "fish", and στέγη (''stégē''), meaning "roof", is an Extinction, extinct genus of limbed tetrapodomorpha, tetrapodomorphs from the Devonian, Late Devonian of what is now Greenland. It was among the earliest four-limbed vertebrates ever in the fossil record and was one of the first with weight-bearing adaptations for terrestrial locomotion. ''Ichthyostega'' possessed lungs and limbs that helped it navigate through shallow water in swamps. Although ''Ichthyostega'' is often labelled a 'tetrapod' because of its limbs and fingers, it evolved long before true crown group tetrapods and could more accurately be referred to as a stegocephalian or stem tetrapod. Likewise, while undoubtedly of amphibian build and habit, it is not a true member of the group in the narrow sense, as the first modern amphibians (members of the group Lissamphibia) appeared in the Triassic Period. Until finds of other early stegocephal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tiktaalik
''Tiktaalik'' (; ) is a monospecific genus of extinct sarcopterygian (lobe-finned fish) from the Late Devonian Period, about 375 Mya (million years ago), having many features akin to those of tetrapods (four-legged animals). ''Tiktaalik'' is estimated to have had a total length of on the basis of various specimens. Unearthed in Arctic Canada, ''Tiktaalik'' is a non-tetrapod member of Osteichthyes (bony fish), complete with scales and gills—but it has a triangular, flattened head and unusual, cleaver-shaped fins. Its fins have thin ray bones for paddling like most fish, but they also have sturdy interior bones that would have allowed ''Tiktaalik'' to prop itself up in shallow water and use its limbs for support as most four-legged animals do. Those fins and other mixed characteristics mark ''Tiktaalik'' as a crucial Transitional fossil, transition fossil, a link in evolution from swimming fish to four-legged vertebrates. This and similar animals might be the common ancestors of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
