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Encyclopedia > Tetrapod
?Tetrapods
Fossil range: Late Devonian to Recent

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
(unranked) Sarcopterygii
(unranked) Tetrapodomorpha
Superclass: Tetrapoda
Broili, 1913
Groups

See text. Disambiguation: Devonian is sometimes used to refer to the Southwestern Brythonic language, and the people of the county of Devon are sometimes referred to as Devonians The Devonian is a geologic period of the Paleozoic era. ... Wikipedia does not have an article with this exact name. ... Binomial name Salamandra salamandra (Linnaeus, 1758) The Fire Salamander (Salamandra salamandra) is probably the most well-known salamander species in Europe. ... Scientific classification or biological classification is how biologists group and categorize extinct and living species of organisms (as opposed to folk taxonomy). ... Phyla Subregnum Parazoa Porifera (sponges) Subregnum Agnotozoa Placozoa (trichoplax) Orthonectida (orthonectids) Rhombozoa (dicyemids) Subregnum Eumetazoa Radiata (unranked) (radial symmetry) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anemones) Bilateria (unranked) (bilateral symmetry) Acoelomorpha (basal) Myxozoa (slime animals) Superphylum Deuterostomia (blastopore becomes anus) Chordata (vertebrates, etc. ... Typical Classes Subphylum Urochordata - Tunicates Ascidiacea Thaliacea Larvacea Subphylum Cephalochordata - Lancelets Subphylum Myxini - Hagfishes Subphylum Vertebrata - Vertebrates Petromyzontida - Lampreys Placodermi (extinct) Chondrichthyes - Cartilaginous fishes Acanthodii (extinct) Actinopterygii - Ray-finned fishes Actinistia - Coelacanths Dipnoi - Lungfishes Amphibia - Amphibians Reptilia - Reptiles Aves - Birds Mammalia - Mammals Chordates (phylum Chordata) include the vertebrates, together with... Typical classes Petromyzontidae (lampreys) Placodermi - extinct Chondrichthyes (cartilaginous fish) Acanthodii - extinct Actinopterygii (ray-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) Amphibia (amphibians) Reptilia (reptiles) Aves (birds) Mammalia (mammals) Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Subclasses Coelacanthimorpha - Coelacanths Dipnoi - Lungfishes Tetrapoda Sarcopterygii is traditionally the class of lobe-finned fishes, consisting of lungfish and coelacanths. ... Subgroups See text Tetrapodomorpha is a clade of vertebrates, consisting of sarcopterygians with a number of features of tetrapods. ...

Tetrapods (Greek tetrapoda, Latin quadruped, "four-legged") are vertebrate animals having four feet, legs or leglike appendages. Since amphibians, reptiles, dinosaurs and mammals are all tetrapods, and even birds and snakes are tetrapods by descent, the term is only really useful in describing the earliest tetrapods, which radiated from the Sarcopterygii, or "lobe-finned" fishes, into air-breathing amphibians in the Devonian period. Latin is an ancient Indo-European language. ... The Zebra is an example of a quadruped. ... Classes and Clades Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Phyla Subregnum Parazoa Porifera (sponges) Subregnum Agnotozoa Placozoa (trichoplax) Orthonectida (orthonectids) Rhombozoa (dicyemids) Subregnum Eumetazoa Radiata (unranked) (radial symmetry) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anemones) Bilateria (unranked) (bilateral symmetry) Acoelomorpha (basal) Myxozoa (slime animals) Superphylum Deuterostomia (blastopore becomes anus) Chordata (vertebrates, etc. ... A human foot - Enlarge to view legend For other uses, see Foot (disambiguation). ... Leg has multiple meanings: For the limbs of animals that support them above the ground: in the case of the legs of humans, see Human leg; in the case of the legs of horses, see Equine leg; in the case of the legs of crabs, lobsters, and their close relatives... An appendage is, in general, an external body part that projects from the body, or a natural prolongation or projection from a part of any organism. ... Subclasses and Orders Order Temnospondyli- extinct Subclass Lepospondyli- extinct Subclass Lissamphibia   Anura   Caudata   Gymnophiona Amphibians (class Amphibia) are a taxon of animals that include all tetrapods (four-legged vertebrates) that do not have amniotic eggs. ... Orders See text. ... Orders & Suborders Saurischia Sauropodomorpha Theropoda Ornithischia Thyreophora Ornithopoda Marginocephalia Dinosaurs were vertebrate animals that dominated the terrestrial ecosystem for over 160 million years, first appearing approximately 230 million years ago. ... Orders Subclass Multituberculata (extinct) Plagiaulacida Cimolodonta Subclass Palaeoryctoides (extinct) Subclass Triconodonta (extinct) Subclass Eutheria (excludes extinct ancestors) Afrosoricida Anagaloidea (extinct) Artiodactyla Carnivora Cetacea Chiroptera Cimolesta (extinct) Creodonta (extinct) Condylarthra (extinct) Dermoptera Desmostylia (extinct) Dinocerata (extinct) Embrithopoda (extinct) Hyracoidea Insectivora Lagomorpha Litopterna (extinct) Macroscelidea Mesonychia (extinct) Notoungulata (extinct) Perissodactyla Pholidota Plesiadapiformes... Orders Many - see section below. ... Superfamilies and Families Henophidia Aniliidae Anomochilidae Boidae Bolyeriidae Cylindrophiidae Loxocemidae Pythonidae Tropidophiidae Uropeltidae Xenopeltidae Typhlopoidea Anomalepididae Leptotyphlopidae Typhlopidae Xenophidia Acrochordidae Atractaspididae Colubridae Elapidae Hydrophiidae Viperidae Snakes (from Old English snaca, and ultimately from the Proto-Indo-European base snag- or sneg-, to crawl), also known as ophidians, are cold blooded... Subclasses Coelacanthimorpha - Coelacanths Dipnoi - Lungfishes Tetrapoda Sarcopterygii is traditionally the class of lobe-finned fishes, consisting of lungfish and coelacanths. ... The Guppy, also known as guppie (Poecilia reticulata) is one of the most popular freshwater aquarium fish species in the world. ... Disambiguation: Devonian is sometimes used to refer to the Southwestern Brythonic language, and the people of the county of Devon are sometimes referred to as Devonians The Devonian is a geologic period of the Paleozoic era. ...

Contents


Evolution

Late Devonian vertebrate speciation saw lobe-finned fish like Eusthenopteron having descendants such as Panderichthys which could breathe air in muddy shallows, then Tiktaalik whose limb-like fins could take it onto land, preceding the first tetrapods such as Acanthostega whose feet had eight digits, and Ichthyostega with developed limbs, negotiating weed-filled swamps. Lobe-finned fish evolved into Coelacanth species which survive to this day.
Late Devonian vertebrate speciation saw lobe-finned fish like Eusthenopteron having descendants such as Panderichthys which could breathe air in muddy shallows, then Tiktaalik whose limb-like fins could take it onto land, preceding the first tetrapods such as Acanthostega whose feet had eight digits, and Ichthyostega with developed limbs, negotiating weed-filled swamps. Lobe-finned fish evolved into Coelacanth species which survive to this day.

Image File history File links Fishapods. ... Image File history File links Fishapods. ... Disambiguation: Devonian is sometimes used to refer to the Southwestern Brythonic language, and the people of the county of Devon are sometimes referred to as Devonians The Devonian is a geologic period of the Paleozoic era. ... Classes and Clades Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Subclasses Coelacanthimorpha - Coelacanths Dipnoi - Lungfishes Tetrapoda Sarcopterygii is traditionally the class of lobe-finned fishes, consisting of lungfish and coelacanths. ... Binomial name Eusthenopteron foordi Eusthenopteron foordi Whiteaves 1881 is a genus of lobe-finned fish which has attained an iconic status from its close relationships to tetrapods. ... Panderichthys Panderichthys is a 90-130 cm long fish from the Late Devonian period . ... Binomial name Tiktaalik roseae Daeschler, Shubin & Jenkins, 2006 Tiktaalik (IPA pronunciation: ) is a genus of extinct sarcopterygian (lobe-finned) fishes from the late Devonian period, with many features akin to those of tetrapods (four-legged animals). ... Acanthostega Acanthostega gunnari is an extinct amphibian tetrapod species, among the first animals to have recognizable limbs. ... Species Ichthyostega (Greek: fish roof) is an early tetrapod genus living in the Upper Devonian (Famennian) period, 367-362. ... Families See text Coelacanth (meaning hollow thorn, from the Greek coelia, κοιλιά (hollow) and acanthos, άκανθος (thorn)); IPA: ) is the common name for an order of fish that includes the oldest living lineage of jawed fish known to date. ...

Devonian tetrapods

The first tetrapods are traditionally assumed to have evolved in shallow and swampy freshwater habitats, towards the end of the Devonian, a little more than 360 million years ago. By the late Devonian, land plants had stabilized freshwater habitats, allowing the first wetland ecosystems to develop, with increasingly complex food webs that afforded new opportunities. [1] Freshwater habitats were not the only places to find water filled with organic matter and choked with plants with dense vegetation near the water's edge. Swampy habitats like shallow wetlands, coastal lagoons and large brackish river deltas also existed at this time, and there is much to suggest that this is the kind of environment in which the tetrapods evolved. Early fossil tetrapods have been found in marine sediments, and because fossils of primitive tetrapods in general are found scattered all around the world, they must have spread by following the coastal lines—they could not have lived in freshwater only. A hypothetical phylogenetic tree of all extant organisms, based on 16S rRNA gene sequence data, showing the evolutionary history of the three domains of life, bacteria, archaea and eukaryotes. ... A freshwater swamp This article is about the wetland type (a landform). ... For the village on the Isle of Wight, see Freshwater, Isle of Wight. ... Habitat (from the Latin for it inhabits) is the place where a particular species lives and grows. ... Divisions Green algae Chlorophyta Charophyta Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta - liverworts Anthocerotophyta - hornworts Bryophyta - mosses Vascular plants (tracheophytes) Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongues Seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering plants... A subtropical wetland in Florida, USA, with an endangered American Crocodile. ... In ecology, an ecosystem is a combination of all the living and non-living elements of an area. ... Food chains and food webs or food networks describe the feeding relationships between so the plank species in a biotic community. ...


The common ancestor of all present gnathostomes lived in freshwater, and later migrated back to the sea. To deal with the much higher salinity in sea water, they evolved the ability to turn the nitrogen waste product ammonia into harmless urea, storing it in the body to make the blood as salty as the sea water without poisoning the organism. Ray-finned fishes later returned to freshwater and lost this ability. Since their blood contained more salt than freshwater, they could simply get rid of ammonia through their gills. When they finally returned to the sea again, they could not recover their old trick of turning ammonia to urea, and they had to evolve salt excreting glands instead. Lungfishes do the same when they are living in water, making ammonia and no urea, but when the water dries up and they are forced to burrow down in the mud, they switch to urea production. Like cartilaginous fishes, the coelacanth can store urea in its blood, as can the only known amphibians which can live for long periods of time in salt water (the toad Bufo marinus and the frog Rana cancrivora). These are traits they have inherited from their ancestors. Classes Placodermi Chondrichthyes Acanthodii Osteichthyes Gnathostomata is the group of vertebrates with jaws. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... Ammonia is a compound of nitrogen and hydrogen with the formula NH3. ... Urea is an organic compound of carbon, nitrogen, oxygen and hydrogen, with the formula CON2H4 or (NH2)2CO. Urea is also known as carbamide, especially in the recommended International Non-proprietary Names (rINN) in use in Europe. ... Orders See text. ... Families See text Coelacanth (meaning hollow thorn, from the Greek coelia, κοιλιά (hollow) and acanthos, άκανθος (thorn)); IPA: ) is the common name for an order of fish that includes the oldest living lineage of jawed fish known to date. ... The true toads are amphibians in the Bufonidae family. ... Distribution of frogs (in black) Suborders Archaeobatrachia Mesobatrachia Neobatrachia - List of Anuran families The frog is an amphibian in the order Anura (meaning tail-less from Greek an-, without + oura, tail). ...


If early tetrapods lived in freshwater, and if they lost the ability to produce urea and used ammonia only, they would have to evolve it from scratch again later. Not a single species of all the ray-finned fishes living today has been able to do that, so it is not likely the tetrapods would have done so either. Terrestrial animals that can only produce ammonia would have to drink constantly, making a life on land impossible (a few exceptions exist, as some terrestrial woodlice can excrete their nitrogenous waste as ammonia gas). This probably also was a problem at the start when the tetrapods started to spend time out of water, but eventually the urea system would dominate completely. Because of this it is not likely they emerged in freshwater (unless they first migrated into freshwater habitats and then migrated onto land so shortly after that they still hadn't forgot how to make urea), even if some who never went to land (or extinct primitive species that returned to water) of course could have adapted to freshwater lakes and rivers. Animal environments are classified as either aquatic (water), terrestrial (land), or amphibious (water and land). ... Infraorders and Families Not necessarily a complete list Infraorders: Ligiamorpha Tylomorpha Families: Dubioniscidae Irmaosidae Pseudarmadillidae Scleropactidae Armadillidium vulgare A woodlouse, also known as a pill bug (genus Armadillidium only), armadillo bug, sow bug, slater, ball bug, or roley-poley, is a terrestrial crustacean with a rigid, segmented, calcareous exoskeleton and...


Primitive tetrapods developed from a lobe-finned fish (an "osteolepid Sarcopterygian"), with a two-lobed brain in a flattened skull, a wide mouth and a short snout, whose upward-facing eyes show that it was a bottom-dweller, and which had already developed adaptations of fins with fleshy bases and bones (the "living fossil" coelacanth is a related marine lobe-finned fish without these shallow-water adaptations). Subclasses Coelacanthimorpha - Coelacanths Dipnoi - Lungfishes Tetrapoda Sarcopterygii is traditionally the class of lobe-finned fishes, consisting of lungfish and coelacanths. ... Comparative brain sizes In animals, the brain, or encephalon (Greek for in the head), is the control center of the central nervous system. ... A hippopotamus skull A skull, or cranium, is a bony structure of Craniates which serves as the general framework for a head. ... Grays illustration of a human femur, a typically recognized bone. ...


Even closer related was Panderichthys, who even had a choana. These fishes used their fins as paddles in shallow-water habitats choked with plants and detritus. Their fins could also have been used to attach themselves to plants or similar while they were laying in ambush for prey. The universal tetrapod characteristics of front limbs that bend backward at the elbow and hind limbs that bend forward at the knee can plausibly be traced to early tetrapods living in shallow water. Panderichthys Panderichthys is a 90-130 cm long fish from the Late Devonian period . ... Choana (plural: Choanae) latinization from the Greek choanē meaning funnel is the posterior nasal aperture. ... A paddle is a tool, originally a propulsion implement for mixing or pushing against liquids, typically in order to propel a boat. ... Detritus may refer to: In geology, detritus is the name for loose fragments of rock that have been worn away by erosion. ... A limb (from the Old English lim) is a jointed appendage of the human or animal body; a large or main branch of a tree; a representative, branch or member of a group or organization. ... Elbow redirects here. ... For other uses, see Knee (disambiguation). ...


It is now clear that the common ancestor of the bony fishes had a primitive air-breathing lung (later evolved into a swim bladder in most ray-finned fishes). This suggests that it evolved in warm shallow waters, the kind of habitat the lobe finned fishes were living and made use of their simple lung when the oxygen level in the water became too low. The lungs flank the heart and great vessels in the chest cavity. ... The gas bladder (also fish maw, less accurately swim bladder or air bladder) is an internal organ that contributes to the ability of a fish to control its buoyancy, and thus to stay at the current water depth, ascend, or descend without having to waste energy in swimming. ...


The lungfishes are now considered as being the closest living relatives of the tetrapods, even closer than the coelacanth.


Fleshy lobe fins supported on bones rather than ray-stiffened fins seems to have been an original trait of the bony fishes (Osteichthyes). The lobe-finned ancestors of the tetrapods evolved them further, while the ancestors of the ray-finned (Actinopterygii) fishes evolved their fins in the opposite direction. The most primitive group of the ray-fins, the bichirs, still have fleshy frontal fins. This article is in need of attention. ... Orders See text The Actinopterygii are the ray-finned fish. ... Genera Erpetoichthys Polypterus The bichirs are a family (Polypteridae) of primitive ray-finned fishes, the sole family in the order Polypteriformes. ...


Nine genera of Devonian tetrapods have been described, several known mainly or entirely from lower jaw material. All of them were from the European-North American supercontinent, which comprised Europe, North America and Greenland. The only exception is a single Gondwanan genus, Metaxygnathus, which has been found in Australia. In biology, a genus (plural genera) is a taxonomic grouping. ... It has been suggested that this article or section be merged with mandible. ... In geology, a supercontinent is a land mass comprising more than one continental core, or craton. ... World map showing Europe Political map Europe is one of the seven traditional continents of Earth; the term continent here referring to a cultural and political distinction, rather than a physiographic one, thus leading to various perspectives about Europes precise borders. ... World map showing North America A satellite composite image of North America. ... Pangaea was formed by the merging of two continents, Laurasia and Gondwana East African and Kuungan Orogens 550 Ma reconstruction showing final stages of assembly The southern supercontinent Gondwana (originally Gondwanaland) included most of the landmasses which make up todays continents of the southern hemisphere, including Antarctica, South America... Metaxygnathus is an extinct genus of tetrapodomorph found in Australia. ...


The first Devonian tetrapod identified from Asia was recognized from a fossil jawbone reported in 2002. The Chinese tetrapod Sinostega pani was discovered among fossilized tropical plants and lobe-finned fish in the red sandstone sediments of the Ningxia Hui Autonomous Region of northwest China. This finding substantially extended the geographical range of these animals and has raised new questions about the worldwide distribution and great taxonomic diversity they achieved within a relatively short time. World map showing the location of Asia. ... It has been suggested that Fossil record be merged into this article or section. ... Red sandstone interior of Lower Antelope Canyon, Arizona, worn smooth due to erosion by flash flooding over millions of years Sandstone is a sedimentary rock composed mainly of sand-size mineral or rock grains. ... Ningxia (Simplified Chinese: 宁夏; Traditional Chinese: 寧夏; Pinyin: Níngxià; Wade-Giles: Ning-hsia; Postal Pinyin: Ningsia), full name Ningxia Hui Autonomous Region (Simplified Chinese: 宁夏回族自治区; Traditional Chinese: 寧夏回族自治區; Pinyin: Níngxià Huízú Zìzhìqū), is a Hui autonomous region of the Peoples Republic of China, located on the northwest Loess...

These earliest tetrapods were not terrestrial. The earliest confirmed terrestrial forms are known from the early Carboniferous deposits, some 20 million years later. Still, they may have spent very brief periods out of water and would have used their legs to paw their way through the mud. Image File history File links Download high resolution version (1021x326, 19 KB)i draw it on macromedia flash October 2005 mateus zica File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Download high resolution version (1021x326, 19 KB)i draw it on macromedia flash October 2005 mateus zica File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Species Ichthyostega (Greek: fish roof) is an early tetrapod genus living in the Upper Devonian (Famennian) period, 367-362. ... The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 359. ... In computer gaming, a MUD (Multi-User Dungeon or Domain or Dimension) is a multi-player computer game that combines elements of role-playing games, hack and slash style computer games and social instant messaging chat rooms. ...


Why they went to land in the first place is still debated. One reason could be that the small juveniles who had completed their metamorphosis had what it took to make use of what land had to offer. Already adapted to breathe air and move around in shallow waters near land as a protection (just as modern fish (and amphibians) often spent the first part of their life in the comparative safety of shallow waters like mangrove forests), two very different niches partially overlapped each other, with the young juveniles in the diffuse line between. One of them was overcrowded and dangerous while the other was much safer and much less crowded, offering less competition over resources. The terrestrial niche was also a much more challenging place for primary aquatic animals, but because of the way evolution and the selection pressure works, those juveniles who could take advantage of this would be rewarded. Once they gained a small foothold on land, evolution took care of the rest, thanks to all their preadaptations and being at the right place at the right time. A Pieris rapae larva An older Pieris rapae larva A Pieris rapae pupa A Pieris rapae adult Metamorphosis is a process in biology by which an individual physically develops after birth or hatching, and involves significant change in form as well as growth and differentiation. ... Above and below water view at the edge of the mangal. ...


At this time there were a lot of invertebrates crawling around on land and near water, in moist soil and wet litter, more than big enough to give the small ones a good meal. Some were even big enough to eat small tetrapods, but land would still be a much safer place and offer more than the waters if they knew how to make use of it.


Adults would be too heavy and slow and demand bigger prey. Small juveniles were much lighter, faster and was satisfied with relatively small invertebrates. Modern mudskippers are said to be able to snap insects in flight while on land, so maybe we shouldn't underestimate the early juvenile tetrapods either. Genera Many, e. ...


Initially making only tentative forays onto land, as the generations went by they adapted to terrestrial environments and spent longer periods away from the water, also spending a longer part of their childhood on land before returning to the water for the rest of their life. It is possible also the adults started to spend some time on land as the skeletal modifications in early tetrapods as Ichthyostega suggests, but only to bask in the sun close to the water's edge, not to hunt or move around. Species Ichthyostega (Greek: fish roof) is an early tetrapod genus living in the Upper Devonian (Famennian) period, 367-362. ...


The fully grown obviously kept most of the anatomical and other forms of adaptations from their juvenile stage, giving them modified limbs and other traits of terrestrial properties. To be successful adults they first had to be successful juveniles. The adults of some of the smaller species were in that case probably able to move on land too when sufficiently evolved.


If some sort of neoteny or dwarfism occurred, making the animals sexually mature and fully grown while still living on land, they would only need to visit water to drink and reproduce.

Carboniferous tetrapods

Until the 1990s, there was a 30-million year gap in the fossil record between the late Devonian tetrapods and the reappearance of tetrapod fossils in recognizable mid-Carboniferous amphibian lineages. It was referred to as "Romer's Gap", after the palaeontologist who recognized it. See also 1990s, the band The 1990s decade refers to the years from 1990 to 1999, inclusive, sometimes informally including popular culture from the very late 1980s and from 2000 and beyond. ... The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 359. ... Subclasses and Orders Order Temnospondyli- extinct Subclass Lepospondyli- extinct Subclass Lissamphibia   Anura   Caudata   Gymnophiona Amphibians (class Amphibia) are a taxon of animals that include all tetrapods (four-legged vertebrates) that do not have amniotic eggs. ... Romers Gap is an example of a gap in the fossil record. ... A paleontologist carefully chips rock from a column of dinosaur vertebrae. ...


During the "gap", tetrapod backbones developed, as did limbs with digits and other adaptations for terrestrial life. Ears, skulls and vertebral columns all underwent changes too. The number of digits on hands and feet became standardized at five, as lineages with more digits died out. The very few tetrapod fossils found in the "gap" are all the more precious. A human ear (also called auricle or pinna) The ear is the sense organ that detects sound. ... A hippopotamus skull A skull, or cranium, is a bony structure of Craniates which serves as the general framework for a head. ... A diagram of a thoracic vertebra. ... A human hand has four fingers and a thumb. ...


The transition from an aquatic lobe-finned fish to an air-breathing amphibian was a momentous occasion in the evolutionary history of the vertebrates. For an animal to live in a gravity-neutral, aqueous environment and then invade one that is entirely different required major changes to the overall body plan, both in form and in function. Eryops is an example of an animal that made such adaptations. It retained and refined most of the traits found in its fish ancestors. Sturdy limbs supported and transported its body while out of water. A thicker, stronger backbone prevented its body from sagging under its own weight. Also, by utilizing vestigial fish jaw bones, a rudimentary ear was developed, allowing Eryops to hear airborne sound. Classes and Clades Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Gravity is a force of attraction that acts between bodies that have mass. ... Binomial name Eryops megacephalus Cope, 1882 Eryops (AR-ee-ops) meaning drawn-out face because most of its skull was in front of its eyes (Greek eryein = drawn-out + ops = face) is a genus of extinct, semi-aquatic amphibian found primarily in the Permian-aged Admiral Formation of Archer County... A limb (from the Old English lim) is a jointed appendage of the human or animal body; a large or main branch of a tree; a representative, branch or member of a group or organization. ... The backbone is a synonym for the spine of a vertebrate organism. ... A schematic representation of hearing. ...


By the Visean age of mid-Carboniferous times the early tetrapods had radiated into at least three main branches. Recognizable basal-group Amphibia are representative of the labyrinthodonts, which are comprised of the temnospondyls (e.g. Eryops) and similarly primitive anthracosaurs, who were the relatives and ancestors of the Amniota. Depending on whichever authorities one follows, modern amphibians (frogs, salamanders and caecilians) are derived from one or the other (or possibly both, although this is now a minority position) of these two groups. The first amniotes are known from the early part of the Late Carboniferous, and during the Triassic countered among their number the earliest mammals, turtles, and crocodiles (lizards and birds appeared in the Jurassic, and snakes in the Cretaceous). As living members of the tetrapod clan—that is of the tetrapod "crown-group"—these varied tetrapods represent the phylogenetic end-points of these two divergent lineages. A third, more primitive, Carboniferous group, the baphetids, left no modern survivors. Finally, the Lepospondyli are an extinct Palaeozoic group of uncertain relationships. The Viséan Age is the middle of three ages in the Mississippian Epoch of the Carboniferous Period. ... Subclasses and Orders Order Temnospondyli- extinct Subclass Lepospondyli- extinct Subclass Lissamphibia   Anura   Caudata   Gymnophiona Amphibians (class Amphibia) are a taxon of animals that include all tetrapods (four-legged vertebrates) that do not have amniotic eggs. ... Labyrinthodont (Greek, maze-toothed) is an obsolete term for any member of an extinct superorder or subclass (Labyrinthodontia) of amphibians, which constituted some of the dominant animals of Late Paleozoic and Early Mesozoic times (about 350 to 210 million years ago). ... Groups Edopoidea Edopidae Cochleosauridae Euskelia Eryopoidea Eryopidae Zatrachydidae Dissorophoidea Limnarchia Dvinosauria Archegosauridae Stereospondyli Trematosauroidea Capitosauroidea Metoposauroidea Plagiosauroidea Rhytidosteidae Brachyopoidea Brachyopidae Chigutosauridae Temnospondyli are an important and extremely diverse taxon of small to giant labyrinthodont amphibians that flourished worldwide during the Carboniferous, Permian, and Triassic periods. ... Groups Eoherpeton Embolomeri Gephyrostegidae Anthracosauria refers to a group of extinct reptile-like, amphibian-like tetrapods that flourished during the Carboniferous and early Permian periods, although precisely which species are included depends on ones definition of the taxon. ... Living subgroups Class Synapsida    Class Mammalia(mammals) Class Sauropsida    Anapsida        Testudines(turtles)    Diapsida        Lepidosauria           Squamata(lizards& snakes)           Sphenodontida(tuatara)        Archosauria           Crocodilia(crocodiles)           Class Aves(birds) The amniotes are a microphylum of tetrapod vertebrates that include the Synapsida (mammals) and Reptilia (reptiles and dinosaurs, including birds). ... Orders Anura Caudata Gymnophiona Allocaudata The subclass Lissamphibia includes all recent amphibians. ... Suborders Cryptobranchoidea Salamandroidea Sirenoidea Salamander is the common name applied to approximately 500 amphibian vertebrates with slender bodies, short legs, and long tails (order Caudata or Urodela). ... Families Rhinatrematidae Ichthyophiidae Uraeotyphlidae Scolecomorphidae Typhlonectidae Caeciliidae The Caecilians are an order (Gymnophiona or Apoda) of amphibians which resemble earthworms or snakes. ... The Pennsylvanian is a geologic (sub)period lasting from roughly 325 million years before the present (BP) to 286 million years BP. As with most other geologic periods, the rock beds that define the period are well identified, but the exact date of the start and end are uncertain by... The Triassic is a geologic period that extends from about 245 to 202 Ma (million years ago). ... Orders Subclass Multituberculata (extinct) Plagiaulacida Cimolodonta Subclass Palaeoryctoides (extinct) Subclass Triconodonta (extinct) Subclass Eutheria (excludes extinct ancestors) Afrosoricida Anagaloidea (extinct) Artiodactyla Carnivora Cetacea Chiroptera Cimolesta (extinct) Creodonta (extinct) Condylarthra (extinct) Dermoptera Desmostylia (extinct) Dinocerata (extinct) Embrithopoda (extinct) Hyracoidea Insectivora Lagomorpha Litopterna (extinct) Macroscelidea Mesonychia (extinct) Notoungulata (extinct) Perissodactyla Pholidota Plesiadapiformes... Suborders Cryptodira Pleurodira See text for families. ... Genera Mecistops Crocodylus Osteolaemus See full taxonomy. ... Families Many, see text. ... Orders Many - see section below. ... The Jurassic Period is a major unit of the geologic timescale that extends from about 200 Ma (million years ago), at the end of the Triassic to 146 Ma, at the beginning of the Cretaceous. ... Superfamilies and Families Henophidia Aniliidae Anomochilidae Boidae Bolyeriidae Cylindrophiidae Loxocemidae Pythonidae Tropidophiidae Uropeltidae Xenopeltidae Typhlopoidea Anomalepididae Leptotyphlopidae Typhlopidae Xenophidia Acrochordidae Atractaspididae Colubridae Elapidae Hydrophiidae Viperidae Snakes (from Old English snaca, and ultimately from the Proto-Indo-European base snag- or sneg-, to crawl), also known as ophidians, are cold blooded... The Cretaceous period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic period, about 146 million years ago (Ma), to the beginning of the Paleocene epoch of the Tertiary period (65. ... In biology, phylogenetics (Greek: phylon = tribe, race and genetikos = relative to birth, from genesis = birth) is the study of evolutionary relatedness among various groups of organisms (e. ... The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 359. ... The Baphetids or Loxommatids were large amphibian predators of the Late Carboniferous period (Namurian through Westphalian) of Europe. ... Groups Acherontiscidae Adelospondyli Aïstopoda Lysorophia Microsauria Nectridea Lepospondyli are a group of small but diverse Carboniferous to early Permian tetrapods. ...


Permian tetrapods

In the Permian period, as the separate tetrapod lineages each developed in their own way, the term "tetrapoda" becomes less useful. In addition to temnospondyl and anthracosaur clades among the early "amphibia" (labyrinthodonts), there were two important divergent clades of amniotes, the Sauropsida and the Synapsida, of which the latter were the most important and successful Permian animals. Each of these lineages, however, remains grouped with the tetrapoda, just as Homo sapiens could be considered a very highly-specialized kind of lobe-finned fish. The Permian is a geologic period that extends from about 299. ... Superclasses Anapsida Eurapsida Diapsida Reptilia was an old kingdom or phylum classification that has since been divided into 4 classes. ... Groups Caseasauria Eupelycosauria    Sphenacodontia       Therapsida          (...mammals) Synapsids (fused arch), formerly known as mammal-like reptiles, are a group of amniotes (reptiles and all their ancestors) that developed one hole in their skull (temporal fenestra) behind each eye, about 320 million years ago (Ma) during the late Carboniferous. ...


Living tetrapods

There are three main categories of living ("crown group") tetrapods: A crown group is a living monophyletic group or clade, consisting of the last common ancestor of all living examples, plus all of its descendants. ...

Amphibia 
frogs and toads, newts and salamanders
Sauropsida 
dinosaurs, most modern reptiles, turtles, and birds
Synapsida 
many extinct species, and all mammals

Note that snakes and other legless reptiles are considered tetrapods because they are descended from ancestors who had a full complement of limbs. Similar considerations apply to aquatic mammals. Most tetrapods today are terrestrial, at least in their adult forms, but some species, such as the axolotl, remain aquatic. Tetrapods that returned to the sea include ichthyosaurs and modern whales and dolphins. Subclasses and Orders Order Temnospondyli- extinct Subclass Lepospondyli- extinct Subclass Lissamphibia   Anura   Caudata   Gymnophiona Amphibians (class Amphibia) are a taxon of animals that include all tetrapods (four-legged vertebrates) that do not have amniotic eggs. ... Distribution of frogs (in black) Suborders Archaeobatrachia Mesobatrachia Neobatrachia - List of Anuran families The frog is an amphibian in the order Anura (meaning tail-less from Greek an-, without + oura, tail). ... The true toads are amphibians in the Bufonidae family. ... Suborders Cryptobranchoidea Salamandroidea Sirenoidea Salamander is the common name applied to approximately 500 amphibian vertebrates with slender bodies, short legs, and long tails (order Caudata or Urodela). ... Superclasses Anapsida Eurapsida Diapsida Reptilia was an old kingdom or phylum classification that has since been divided into 4 classes. ... Orders & Suborders Saurischia Sauropodomorpha Theropoda Ornithischia Thyreophora Ornithopoda Marginocephalia Dinosaurs were vertebrate animals that dominated the terrestrial ecosystem for over 160 million years, first appearing approximately 230 million years ago. ... Orders See text. ... Suborders Cryptodira Pleurodira See text for families. ... Orders Many - see section below. ... Groups Caseasauria Eupelycosauria    Sphenacodontia       Therapsida          (...mammals) Synapsids (fused arch), formerly known as mammal-like reptiles, are a group of amniotes (reptiles and all their ancestors) that developed one hole in their skull (temporal fenestra) behind each eye, about 320 million years ago (Ma) during the late Carboniferous. ... Orders Subclass Multituberculata (extinct) Plagiaulacida Cimolodonta Subclass Palaeoryctoides (extinct) Subclass Triconodonta (extinct) Subclass Eutheria (excludes extinct ancestors) Afrosoricida Anagaloidea (extinct) Artiodactyla Carnivora Cetacea Chiroptera Cimolesta (extinct) Creodonta (extinct) Condylarthra (extinct) Dermoptera Desmostylia (extinct) Dinocerata (extinct) Embrithopoda (extinct) Hyracoidea Insectivora Lagomorpha Litopterna (extinct) Macroscelidea Mesonychia (extinct) Notoungulata (extinct) Perissodactyla Pholidota Plesiadapiformes... Superfamilies and Families Henophidia Aniliidae Anomochilidae Boidae Bolyeriidae Cylindrophiidae Loxocemidae Pythonidae Tropidophiidae Uropeltidae Xenopeltidae Typhlopoidea Anomalepididae Leptotyphlopidae Typhlopidae Xenophidia Acrochordidae Atractaspididae Colubridae Elapidae Hydrophiidae Viperidae Snakes (from Old English snaca, and ultimately from the Proto-Indo-European base snag- or sneg-, to crawl), also known as ophidians, are cold blooded... Animal environments are classified as either aquatic (water), terrestrial (land), or amphibious (water and land). ... In biology, a species is one of the basic units of biodiversity. ... Binomial name Ambystoma mexicanum (Shaw, 1789) The Axolotl (Ambystoma mexicanum) is an aquatic salamander native to Mexico. ... Taxonomy See text Ichthyosaurs (Greek for fish lizard - ιχθυς meaning fish and σαυρος meaning lizard) were giant marine reptiles that resembled fish and dolphins. ... Whales are the largest species of exclusively aquatic mammals, members of the order Cetacea, which also includes dolphins and porpoises. ... Genera See article below. ...


Classification

Labyrinthodontia Diagnostic features unique to the Labyrinthodontia are hard to find at first glance; the complex dentine infolding tooth structure was shared with crossopterygian fish. The labyrinthodonts are divided into the Temnospondyli and the Anthracosauria, the main difference between the two groups being their respective vertebral structures. The Anthracosauria had small pleurocentra, which grew and fused, becoming the true centrum in later vertebrates. In contrast, the Temnospondyli had a conservative vertebral column in which the pleurocentra remained small in primitive forms, vanishing entirely in the more advanced ones. The intercentra are large and form a complete ring. This article or section does not cite its references or sources. ... Groups Edopoidea Edopidae Cochleosauridae Euskelia Eryopoidea Eryopidae Zatrachydidae Dissorophoidea Limnarchia Dvinosauria Archegosauridae Stereospondyli Trematosauroidea Capitosauroidea Metoposauroidea Plagiosauroidea Rhytidosteidae Brachyopoidea Brachyopidae Chigutosauridae Temnospondyli are an important and extremely diverse taxon of small to giant labyrinthodont amphibians that flourished worldwide during the Carboniferous, Permian, and Triassic periods. ... Groups Eoherpeton Embolomeri Gephyrostegidae Anthracosauria refers to a group of extinct reptile-like, amphibian-like tetrapods that flourished during the Carboniferous and early Permian periods, although precisely which species are included depends on ones definition of the taxon. ... Centrum means center in Latin and several other European languages. ...


Temnospondyls A diagnostic feature of the Temnospondyli was that the tabular bone in the skull roof is relatively small and had no contact with the parietal bone, whereas contact between the two bones was present in all anthracosaurs. The parietal bones (os parietale) are bones in the human skull and form, by their union, the sides and roof of the cranium. ...


Although the temnospondyls flourished in many forms in the Late Paleozoic and Triassic, they were an entirely self-contained group and did not give rise to any later tetrapod groups. It was the sister group Anthracosauria that gave rise to the reptiles. The Paleozoic Era is a major division of the geologic timescale, one of four geologic eras. ... The Triassic is a geologic period that extends from about 245 to 202 Ma (million years ago). ... Groups Eoherpeton Embolomeri Gephyrostegidae Anthracosauria refers to a group of extinct reptile-like, amphibian-like tetrapods that flourished during the Carboniferous and early Permian periods, although precisely which species are included depends on ones definition of the taxon. ...


Within the Temnospondyli are the two suborders Rachitomi and Stereospondyli, also distinguished by their vertebrae. There were three distinct successive stages within the Rachitomi, the first occurring in the Carboniferous. The second happened mostly in the Pennsylvanian, continuing into Permian, of which Erydops is characteristic. The third and final stage was in the Late Carboniferous and Early Permian, from which Eryops of the Texas Permian red beds is best known. Just as there were numerous side branches throughout the evolution of the temnospondyls, so too were there many of the rachitomes. The Rachitomi were a group of extinct Palaeozoic labyrinthodont amphibians, according to an earlier classification system. ... The Stereospondyli were a group of extinct Palaeozoic labyrinthodont amphibians, according to an earlier classification system. ... The Pennsylvanian is a geologic (sub)period lasting from roughly 325 million years before the present (BP) to 286 million years BP. As with most other geologic periods, the rock beds that define the period are well identified, but the exact date of the start and end are uncertain by... Banded Iron Formations are a distinctive type of rock often found in old sedimentary rocks. ... A hypothetical phylogenetic tree of all extant organisms, based on 16S rRNA gene sequence data, showing the evolutionary history of the three domains of life, bacteria, archaea and eukaryotes. ...


Of special interest in regard to the Rachitomi is Branchiosaurus, which see. Branchiosaurus is a genus of small lightly-built early amphibians that had gills. ...


Tetrapod groups

A partial taxonomy of the tetrapods:

Typical Classes Subphylum Urochordata - Tunicates Ascidiacea Thaliacea Larvacea Subphylum Cephalochordata - Lancelets Subphylum Myxini - Hagfishes Subphylum Vertebrata - Vertebrates Petromyzontida - Lampreys Placodermi (extinct) Chondrichthyes - Cartilaginous fishes Acanthodii (extinct) Actinopterygii - Ray-finned fishes Actinistia - Coelacanths Dipnoi - Lungfishes Amphibia - Amphibians Reptilia - Reptiles Aves - Birds Mammalia - Mammals Chordates (phylum Chordata) include the vertebrates, together with... Subclasses Coelacanthimorpha - Coelacanths Dipnoi - Lungfishes Tetrapoda Sarcopterygii is traditionally the class of lobe-finned fishes, consisting of lungfish and coelacanths. ... Subgroups See text Tetrapodomorpha is a clade of vertebrates, consisting of sarcopterygians with a number of features of tetrapods. ... Binomial name Eusthenopteron foordi Eusthenopteron foordi Whiteaves 1881 is a genus of lobe-finned fish which has attained an iconic status from its close relationships to tetrapods. ... Panderichthys Panderichthys is a 90-130 cm long fish from the Late Devonian period . ... Binomial name Tiktaalik roseae Daeschler, Shubin & Jenkins, 2006 Tiktaalik (IPA pronunciation: ) is a genus of extinct sarcopterygian (lobe-finned) fishes from the late Devonian period, with many features akin to those of tetrapods (four-legged animals). ... Complete name: Elginerpeton Pancheni Elginerpeton pancheni, dating from the Upper Frasnian (Late Devonian) of Scat Craig, Scotland. ... Acanthostega Acanthostega gunnari is an extinct amphibian tetrapod species, among the first animals to have recognizable limbs. ... Species Ichthyostega (Greek: fish roof) is an early tetrapod genus living in the Upper Devonian (Famennian) period, 367-362. ... Hynerpeton is one of the earliest known amphibians ever to walk the Earth. ... Paleo Template Project Crassigyrinus was an amphibian from the early Carboniferous period, from Scotland. ... The Baphetids or Loxommatids were large amphibian predators of the Late Carboniferous period (Namurian through Westphalian) of Europe. ... Subclasses and Orders Order Temnospondyli- extinct Subclass Lepospondyli- extinct Subclass Lissamphibia   Anura   Caudata   Gymnophiona Amphibians (class Amphibia) are a taxon of animals that include all tetrapods (four-legged vertebrates) that do not have amniotic eggs. ... Groups Acherontiscidae Adelospondyli Aïstopoda Lysorophia Microsauria Nectridea Lepospondyli are a group of small but diverse Carboniferous to early Permian tetrapods. ... Groups Edopoidea Edopidae Cochleosauridae Euskelia Eryopoidea Eryopidae Zatrachydidae Dissorophoidea Limnarchia Dvinosauria Archegosauridae Stereospondyli Trematosauroidea Capitosauroidea Metoposauroidea Plagiosauroidea Rhytidosteidae Brachyopoidea Brachyopidae Chigutosauridae Temnospondyli are an important and extremely diverse taxon of small to giant labyrinthodont amphibians that flourished worldwide during the Carboniferous, Permian, and Triassic periods. ... Orders Anura Caudata Gymnophiona Allocaudata The subclass Lissamphibia includes all recent amphibians. ... Groups Amniota Anthracosauria Batrachosauria Chroniosuchidae Diadectomorpha Embolomeri Gephyrostegidae Seymouriamorpha Solenodonsauridae Tokosauridae Westlothiana lizziae Reptiliomorpha is a name given either to reptile-like amphibians, or to amniotes and those amphibians related to them. ... Living subgroups Class Synapsida    Class Mammalia(mammals) Class Sauropsida    Anapsida        Testudines(turtles)    Diapsida        Lepidosauria           Squamata(lizards& snakes)           Sphenodontida(tuatara)        Archosauria           Crocodilia(crocodiles)           Class Aves(birds) The amniotes are a microphylum of tetrapod vertebrates that include the Synapsida (mammals) and Reptilia (reptiles and dinosaurs, including birds). ... Orders See text. ... Orders Many - see section below. ... Groups Caseasauria Eupelycosauria    Sphenacodontia       Therapsida          (...mammals) Synapsids (fused arch), formerly known as mammal-like reptiles, are a group of amniotes (reptiles and all their ancestors) that developed one hole in their skull (temporal fenestra) behind each eye, about 320 million years ago (Ma) during the late Carboniferous. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary...

Anatomy

Anatomical features of early tetrapods

The amphibian's ancestral fish must have possessed similar traits to those inherited by the early amphibians, including internal nostrils (to separate the breathing and feeding passages) and a large fleshy fin built on bones that could give rise to the tetrapod limb. The rhipidistian crossopterygians fulfill every requirement for this ancestry. Their palatal and jaw structures were identical to those of amphibians, and their dentition was identical too, with labyrinthine teeth fitting in a pit-and-tooth arrangement on the palate. The crossopterygian paired fins were smaller than tetrapod limbs, but the skeletal structure was very similar in that the crossopterygian had a single proximal bone (analogous to the humerus or femur), two bones in the next segment (forearm or lower leg), and an irregular subdivision of the fin, roughly comparable to the structure of the carpus / tarsus and phalanges of a hand. A fin is a surface used to produce lift and thrust or to steer while traveling in water, air, or other fluid media. ... ... The palate is the roof of the mouth in humans and vertebrate animals. ... Dentition is the development of teeth and their arrangement in the mouth. ... The humerus is a long bone in the arm or fore-legs (animals) that runs from the shoulder to the elbow. ... The femur or thigh bone is the longest, most voluminous. ... In Greek mythology, Carpus fruit was a son of Chloris and Boreas. ... FIG. 268– Bones of the right foot. ... A human hand has four fingers and a thumb. ...


The major difference between crossopterygians and amphibians was in relative development of front and back skull portions; the snout is much less developed than in most amphibians and the post-orbital skull is exceptionally longer than an amphibian's. A hippopotamus skull A skull, or cranium, is a bony structure of Craniates which serves as the general framework for a head. ...


A great many kinds of early amphibians lived during the Carboniferous period. Therefore, their ancestor would have lived earlier, during the Devonian period. Devonian Ichthyostegids were the earliest of amphibians, with a skeleton that is directly comparable to that of rhipidistian ancestors. Early Labyrinthodonts (Late Devonian to Early Mississippian) still had some ichthyostegid features such as similar skull bone patterns, labyrinthine tooth structure, the fish skull-hinge, pieces of gill structure between the cheek and shoulder, and the vertebral column. They had, however, lost several other fish features such as the fin rays in the tail. The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 359. ... Disambiguation: Devonian is sometimes used to refer to the Southwestern Brythonic language, and the people of the county of Devon are sometimes referred to as Devonians The Devonian is a geologic period of the Paleozoic era. ... Labyrinthodont (Greek, maze-toothed) is an obsolete term for any member of an extinct superorder or subclass (Labyrinthodontia) of amphibians, which constituted some of the dominant animals of Late Paleozoic and Early Mesozoic times (about 350 to 210 million years ago). ... This article is about the geologic period; for the North American culture, see Mississippian culture. ... gills of a Smooth Newt Gills inside of a tuna head In aquatic organisms, gills are a respiratory organ for the extraction of oxygen from water and for the excretion of carbon dioxide. ... The vertebral column seen from the side Different regions (curvatures) of the vertebral column The vertebral column (backbone or spine) is a column of vertebrae situated in the dorsal aspect of the abdomen. ... A Ring-tailed Lemur For other uses, see Tail (disambiguation). ...


In order to propagate in the terrestrial environment, certain challenges had to be overcome. The animal's body needed additional support, because buoyancy was no longer a factor. A new method of respiration was required in order to extract atmospheric oxygen, instead of oxygen dissolved in water. A means of locomotion would need to be developed to traverse distances between waterholes. Water retention was now important since it was no longer the living matrix, and it could be lost easily to the environment. Finally, new sensory input systems were required if the animal was to have any ability to function reasonably while on land. In physics, buoyancy is an upward force on an object immersed in a fluid (i. ... Respiration is the process by which an organism obtains energy by reacting oxygen with glucose to give water, carbon dioxide and ATP (energy). ... Layers of Atmosphere (NOAA) Air redirects here. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance transparent (gas) very pale blue (liquid) Atomic mass 15. ... In a general sense, locomotion simply means active movement or travel, applying not just to biological individuals. ... In biology, the word matrix is used for the material between animal or plant cells, or generally the material (or tissue) in which more specialized structures are embedded, and also specifically for one part of the mitochondrion. ...


Skull

The most notable characteristics that make an amphibian skull different from a fish's are the relative frontal and rear portion lengths. The fish had a long rear portion while the front was short; the orbital vacuities were thus located towards the anterior end. In the amphibian, the front of the skull lengthened, positioning the orbits farther back on the skull. The lacrimal bone was not in contact with the frontal anymore, having been separated from it by the prefrontal bone. Also of importance is that the skull was now free to rotate from side to side, independent of the spine, on the newly forming neck. In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. ... The lacrimal bone (Os Lacrimale), the smallest and most fragile bone of the face, is situated at the front part of the medial wall of the orbit . ...


A diagnostic character of temnospondyls is that the tabular bones (which formed the posterior corners of the skull-table) were separated from the respective left and right parietals by a sutural junction between the postparietals and supratemporals. Also at the rear of the skull, all bones dorsal to the cleithrum were lost. The parietal bones (os parietale) are bones in the human skull and form, by their union, the sides and roof of the cranium. ...


The lower jaw of, for example, Eryops resembled its crossopterygian ancestors in that on the outer surface lay a long dentary which bore teeth. There were also bones below the dentary on the jaw: two splenials, the angulary and the surangular. On the inside were usually three coronoids which bore teeth and lay close to the dentary. On the upper jaw was a row of marginal labyrinthine teeth, located on the maxilla and premaxilla. In Eryops, as in all early amphibians, the teeth were replaced in waves which traveled from the front of the jaw to the back in such a way that every other tooth was mature, and the ones in between were young. The dentary is the tooth bearing bone of the lower jaw. ... The splenial is a small bone in the lower jaw of reptiles, amphibians and birds, usually located on the lingual side (closest to the tongue) between the angular and suprangular. ... The Coronoid process can refer to: The Ramus mandibulae of the mandible A part of the ulna Category: ... The maxillae are the largest bones of the face, except for the mandible, and form, by their union, the whole of the upper jaw. ... The premaxilla is a pair of small bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. ...


Dentition

The Labyrinthodontia had a peculiar tooth structure from which their name was derived and, although not exculsive to the group, the labyrinthine dentition is a useful indicator as to proper classification. The important feature of the tooth is that the enamel and dentine were folded in such a way as to form a complicated corrugated pattern when viewed in cross section. This infolding resulted in strengthening of the tooth and increased wear resistance. Such teeth survived for 100 Ma, first among crossopterygian fish, then stem reptiles. Modern amphibians no longer have this type of dentition but rather pleurodont teeth, in fewer numbers of the whole group. Tooth enamel is the hardest and most highly mineralized substance of the body , and with dentin, cementum, and dental pulp is one of the four major parts of the tooth. ... Dentin (BE: dentine) is the name of substance between the enamel (crown) or cementum (root) of a tooth and the pulp chamber. ...


Sensory organs

There is a density difference between air and water that causes smells (certain chemical compounds detectable by chemoreceptors) to behave differently. An animal first venturing out onto land would have difficulty in locating such chemical signals if its sensory apparatus was designed for aquatic detection. Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... Look up smell in Wiktionary, the free dictionary. ... A Chemosensor, also known as chemoreceptor, is a cell or group of cells that transduce a chemical signal into an action potential. ... An apparatus is: A machine; or Reference tools added to a book, apart from the text, such as variant readings or translations, textual notes, a concordance, a bibliography, or an index, designed for the use of scholars studying the book. ...


Fish have a lateral line system which detects pressure fluctuations in the water. Such pressure is non-detectable in air, but grooves for the lateral line sense organs were found on the skull of labyrinthodonts, suggesting a partially aquatic habitat. Modern amphibians, which are semi-aquatic, exhibit this feature whereas it has been retired by the higher vertebrates. The olfactory epithelium would also have to be modified in order to detect airborne odors. In fish, the lateral line is a sense organ used to detect movement in the surrounding water. ... Pressure (symbol: p) is the force per unit area applied on a surface in a direction perpendicular to that surface. ... Habitat (from the Latin for it inhabits) is the place where a particular species lives and grows. ... Olfaction, the sense of odor (smell), is the detection of chemicals dissolved in air (or in water, by animals that live under water). ... In zootomy, epithelium is a tissue composed of a layer of cells. ... JUNIOR Odor receptors on the antennae of a Luna moth An odor (American English) or odour (Commonwealth English) is the object of perception of the sense of olfaction. ...


In addition to the lateral line organ system, the eye had to change as well. This change came about because the refractive index of light differs between air and water, so the focal length of the lens was altered in order to properly function. The eye was now exposed to a relatively dry environment rather than being bathed by water, so eyelids developed and tear ducts evolved to produce a liquid, moistening the eyeball. The refractive index (or index of refraction) of a material is the factor by which the phase velocity of electromagnetic radiation is slowed in that material, relative to its velocity in a vacuum. ... The focal point F and focal length f of a positive lens, a negative lens, a concave mirror, and a convex mirror. ... Light from a single point of a distant object and light from a single point of a near object being brought to a focus by changing the curvature of the lens. ... An eyelid is a thin fold of skin and muscle that covers and protects an eye. ... Tears trickling down the cheeks Lacrimation is the bodys process of producing tears, which are a liquid to clean and lubricate the eyes. ...


Hearing

The balancing function of the middle ear was retained from the fish ancestry, but delicate air vibrations could not set up pulsations through the skull in order for it to function a proper auditory organ. Typical of most labyrinthodonts, the spiracular gill pouch was retained as the otic notch, closed in by the tympanum, a thin, tight membrane. Oscillation is the periodic variation, typically in time, of some measure as seen, for example, in a swinging pendulum. ... Angular frequency is a measure of how fast an object is rotating In physics (specifically mechanics and electrical engineering), angular frequency ω (also called angular speed) is a scalar measure of rotation rate. ... In biology, an organ (Latin: organum, instrument, tool) is a group of tissues that perform a specific function or group of functions. ... Tympanum may mean: The eardrum; or A sculpted panel that stands within the recessed area formed by a larger arch above the doors to a church or similar building, especially in Romanesque and Gothic architecture; or A single drum in the orchestral percussion section usually called timpani. ... It has been suggested that Net flux be merged into this article or section. ...


The hyomandibula of fish migrated upwards from its jaw supporting position, and was reduced in size to form the stapes. Situated between the tympanum and braincase in an air-filled cavity, the stapes was now capable of transmitting vibrations from the exterior of the head to the interior. Thus the stapes became an important element in an impedance matching system, coupling airborne sound waves to the receptor system of the inner ear. This system had evolved independently within several different amphibian lineages. The stapes or stirrup is the stirrup-shaped small bone or ossicle in the middle ear which attaches the incus to the fenestra ovalis, the oval window which is adjacent to the vestibule of the inner ear. ... Impedance mismatch has two meanings. ... The term lineage can refer to several things. ...


In order for the impedance matching ear to work, certain conditions had to be met. The stapes must have been perpendicular to the tympanum, small and light enough to reduce its inertia and suspended in an air-filled cavity. In modern species which are sensitive to over 1 kHz frequencies, the footplate of the stapes is 1/20th the area of the tympanum. However, in early amphibians the stapes was too large, making the footplate area oversized, preventing the hearing of high frequencies. So it appears that only high intensity, low frequency sounds could be detected, with the stapes more probably being used to support the braincase against the cheek. . ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ...


"Did Our Ancestors Breathe through Their Ears?"


Girdles

The pectoral girdle of early tetrapods such as Eryops was highly developed, with a larger size for both increased muscle attachment to it and to the limbs. Most notably, the shoulder girdle was disconnected from the skull, resulting in improved terrestrial locomotion. The crossopterygian cleithrum was retained as the clavicle, and the interclavicle was well-developed, lying on the underside of the chest. In primitive forms, the two clavicles and the interclavical could have grown ventrally in such a way as to form a broad chest plate, although such was not the case in Eryops. The upper portion of the girdle had a flat, scapular blade, with the glenoid cavity situated below performing as the articulation surface for the humerus, while ventrally there was a large, flat coracoid plate turning in toward the midline. Location The clavicular head of the pectoralis major takes its origin from the anterior surface of the medial half of the clavicle. ... A girdle is a piece of womens underwear that replaced the corset in popularity and usage. ... A top-down view of skeletal muscle Muscle (from Latin musculus little mouse, referring to muscles like the biceps which pop up as though a mouse were scurrying about under the skin [1]) is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. ... Left clavicle - from above Left clavicle - from below Collarbone and collar bone redirect here. ... Glenoid fossa redirects here, for the other use of Glenoid fossa please see mandibular fossa. ... Articulation may refer to several topics: In speech, linguistics, and communication: Topic-focus articulation Articulation score Place of articulation Manner of articulation In music: Musical articulations (staccato, legato, etc) In education: Articulation (education) In sociology: Articulation (sociology) This is a disambiguation page — a navigational aid which lists other pages that...


The pelvic girdle also was much larger than the simple plate found in fishes, accommodating more muscles. It extended far dorsally and was joined to the backbone by one or more specialized sacral ribs. The hind legs were somewhat specialized in that they not only supported weight, but also provided propulsion. The dorsal extension of the pelvis was the ilium, while the broad ventral plate was comprised of the pubis in front and the ischium in behind. The three bones met at a single point in the center of the pelvic triangle called the acetabulum, providing a surface of articulation for the femur. Human male pelvis, viewed from front Human female pelvis, viewed from front The pelvis is the bony structure located at the base of the spine (properly known as the caudal end). ... The human rib cage. ... A man and a woman in the Pioneer plaque. ...


The main strength of the ilio-sacral attachment of Eryops was by ligaments, a condition structurally, but not phylogenetically, intermediate between that of the most primitive embolomerous amphibians and early reptiles. The condition that is more usually found in higher vertebrates is that cartilage and fusion of the sacral ribs to the blade of the ilium are utilized in addition to ligamentous attachments. A ligament is a short band of tough fibrous connective tissue composed mainly of long, stringy collagen fibres. ... In biology, phylogenetics (Greek: phylon = tribe, race and genetikos = relative to birth, from genesis = birth) is the study of evolutionary relatedness among various groups of organisms (e. ... Cartilage is a type of dense connective tissue. ...


Limbs

The humerus was the largest bone of the arm, its head articulating with the glenoid cavity of the pectoral girdle, distally with the radius and ulna. The radius resided on the inner side of the forearm and rested directly under the humerus, supporting much of the weight, while the ulna was located to the outside of the humerus. The ulna had a head, which muscles pulled on to extend the limb, called the olecranon that extended above the edge of the humerus. The radius and ulna of the left forearm, posterior surface. ... The ulna (Elbow Bone) [Figs. ... ...


The radius and the ulna articulated with the carpus which was a proximal row of three elements: the radiale underlying the radius, the ulnare underneath the ulna and an intermedium between the two. A large central element was beneath the last and may have articulated with the radius. There were also three smaller centralia lying to the radial side. Opposite the head of each toe lay a series of five distal carpals. Each digit had a first segment, the metacarpal, lying in the palm region. In Greek mythology, Carpus fruit was a son of Chloris and Boreas. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... Toes on foot. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... In human anatomy, the carpal bones are the bones of the human wrist. ... Digit may refer to: A finger or a toe Numerical digit, as used in mathematics or computer science Digit (unit), an ancient meterological unit Digit (magazine), an Indian information technology magazine This is a disambiguation page: a list of articles associated with the same title. ... The metacarpus is the intermediate part of the hand skeleton that is located between the fingers distally and the carpus which forms the connection to the forearm. ...


The pelvic limb bones were essentially the same as in the pectoral limb, but with different names. The analogue to the humerus was the femur which was longer and slimmer. The two lower arm bones corresponded to the tibia and fibula of the hind leg, the former being the innermost and the latter the outermost bones. The tarsus is the hind version of the carpus and its bones correspond as well. Analogy is either the cognitive process of transferring information from a particular subject (the analogue or source) to another particular subject (the target), or a linguistic expression corresponding to such a process. ... Figure 1 : Upper surface of right tibia. ... Figure 1 : Lower extremity of right fibula. ... In tetrapods, the tarsi are the cluster of bones in the foot between the tibia and fibula and the metatarsus. ...


Feeding

Early amphibians had a wide, gaping jaw with weak muscles with which to open and close it. Within the jaw were fang-like palatal teeth which, when coupled with the gape, suggests an intertial feeding habit. This is when the amphibian would grasp the prey and, lacking any chewing mechanism, toss the head up and backwards, throwing the prey farther back into the mouth. Such feeding is seen today in the crocodile and alligator. Prey can refer to: Look up Prey in Wiktionary, the free dictionary A prey animal eaten by a predator in an act called predation. ... Species Alligator mississippiensis Alligator sinensis An alligator is a crocodilian in the genus Alligator of the family Alligatoridae. ...


The tongue of modern adult amphibians is quite fleshy and attached to the front of the lower jaw, so it is reasonable to speculate that it was fastened in a similar fashion in primitive forms, although it was probably not specialized like it is in a frog. Tongue The tongue is the large bundle of muscles on the floor of the mouth that manipulates food for chewing and swallowing. ...


It is taken that early amphibians were not very active, thus a predatory lifestyle was probably not the norm. It is more likely that it fed on fish either in the water or on those which became stranded at the margins of lakes and swamps. Also abundant at the time was a large supply of terrestrial invertebrates which may have provided a fairly adequate food supply. This snapping turtle is trying to make a meal of a Canada goose, but the goose is too wary. ... This article or section does not cite its references or sources. ... Invertebrate is a term coined by Chevalier de Lamarck to describe any animal without a backbone or vertebra, like insects, squids and worms. ...


Respiration

Modern amphibians breathe by inhaling air into lungs, where oxygen is absorbed. They also breathe through the moist lining of the mouth and skin. So too did Eryops, but its ribs were too closely spaced to suggest that it simply expanded the rib cage. More likely, it depressed the hyoid apparatus to expand the oral cavity and elevated the floor of the mouth while it and the nostrils were closed. This forced air back into the lungs. Air could then be forced back out by contraction of the elastic tissue in the lung walls. Other special respiratory methods probably existed. Respiration is the process by which an organism obtains energy by reacting oxygen with glucose to give water, carbon dioxide and ATP (energy). ... The heart and lungs (from an older edition of Grays Anatomy) The lung is an organ belonging to the respiratory system and interfacing to the circulatory system of air-breathing vertebrates. ... A close-up of human skin. ... This article is about the bones called ribs. ... The hyoid bone (Os Hyoideum; Lingual Bone) is a bone in the human neck, not articulated to any other bone; it is supported by the muscles of the neck and in turn supports the root of the tongue. ... Biological tissue is any substance made up of cells that perform a similar function within an organism. ...


Circulation

Early tetrapods most likely had a three-chambered heart, as do modern amphibians and reptiles, in which oxygenated blood from the lungs and de-oxygenated blood from the respiring tissues enters by separate atria, and is directed via a spiral valve to the appropriate vessel—aorta for oxygenated blood and pulmonary vein for deoxygenated blood. The spiral valve is essential to keeping the mixing of the two types of blood to a minimum, enabling the animal to have higher metabolic rates, and be more active than otherwise. The heart and lungs, from an older edition of Greys Anatomy. ...


Locomotion

Typical early amphibian posture is exhibited by the upper arm and upper leg extending nearly straight out from its body, while the forearm and the lower leg extended downward from the upper segment at a near right angle. The body weight was not centered over the limbs, but was rather transferred 90 degrees outward and down through the lower limbs, which contacted the ground. Most of the animal's strength was used to just elevate its body off the ground for walking, which was probably slow and difficult. With this sort of posture, only short, broad strides could be achieved. This has been confirmed by fossilized footprints found in Carboniferous rocks. This article is about angles in geometry. ... The magnitude of physical strength, often referred to as just strength, determines the ability of a person or animal to exert force on physical objects using muscles. ... Sedimentary, volcanic, plutonic, metamorphic rock types of North America. ...


Ligamentous attachments within the limbs were present in Eryops, being important because they were the precursor to bony and cartilagenous variations seen in modern terrestrial animals that use their limbs for locomotion.


Of all body parts, the spine was the most affected by the move from water to land. It now had to resist the bending caused by body weight and had to provide mobility where needed. Previously, it was able to bend along its entire length. Likewise, the paired appendages had not been formerly related to the spine, but the slowly strengthening limbs now transmitted their support to the axis of the body.


tetrapod in Japan

In Japanese, 'tetrapod' in katakana means wave-dissipating blocks, because they are mostly made by Tetra Co, Ltd. The use of the word comes from the shape of the blocks (four concrete legs in tetrahedral arrangement). This article or section does not cite its references or sources. ...


See also

The geologic time scale is used by geologists and other scientists to describe the timing and relationships between events that have occurred during the history of the Earth. ... Jennifer A. Clack is a British expert in the theory of evolution. ... Prehistoric life is a term used to refer to diverse organisms that inhabited Earth from the origin of life about 3. ... The term body form is used to describe a design of the animal form, a blueprint of life. ...

External links

Example of family tree A family tree is generally the totality of ones ancestors, or more specifically, a chart used in genealogy to show the family connections between individuals, consisting of the individuals names (usually accompanied by dates, and often also places and occupations) connected by various types of...

Devonian tetrapods

Carboniferous tetrapods

  • Detailed account of early tetrapod evolution - This website, geared to the layman, also describes Jennifer Clack's role in untangling the early evolution of tetrapods.
  • Abstract of Jennifer A. Clack, "An early tetrapod from 'Romer's Gap'" in Nature, July 2002
  • Abstract of Jennifer Clack's identification of a primitive baphetid tetrapod
  • "The evolution of tetrapods and the closing of Romer's Gap."

  Results from FactBites:
 
Tetrapod - Wikipedia, the free encyclopedia (4611 words)
Since amphibians, reptiles, dinosaurs and mammals are all tetrapods, and even birds and snakes are tetrapods by descent, the term is only really useful in describing the earliest tetrapods, which radiated from the Sarcopterygii, or "lobe-finned" fishes, into air-breathing amphibians in the Devonian period.
The universal tetrapod characteristics of front limbs that bend backward at the elbow and hind limbs that bend forward at the knee can plausibly be traced to early tetrapods living in shallow water.
Early tetrapods most likely had a three-chambered heart, as do modern amphibians and reptiles, in which oxygenated blood from the lungs and de-oxygenated blood from the respiring tissues enters by separate atria, and is directed via a spiral valve to the appropriate vessel—aorta for oxygenated blood and pulmonary vein for deoxygenated blood.
Tetrapod (119 words)
A tetrapod is a vertebrate animal having four feet, legs or leglike appendages.
According to the theory of evolution, the first tetrapod was a fish, probably descended from a coelacanth or similar creature, that inhabited tidal mudflats.
Today, most tetrapods are land-dwelling, at least in their adult forms, but some species (such as the axolotl, whale and ichthyosaur[?]) have returned to the sea.
  More results at FactBites »

 
 

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