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Tetrapod - Wikipedia, the free encyclopedia 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. en.wikipedia.org /wiki/Tetrapod   (4611 words)

Tetrapod 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. www.ebroadcast.com.au /lookup/encyclopedia/te/Tetrapoda.html   (119 words)

Untitled Document Since amphibians, reptiles, dinosaurs and mammals are all tetrapods, and even birds and snakes are tetrapods by decline, the word is only truly useful in describing the earliest tetrapods, which radiated from the Sarcopterygii, or "lobe-finned" fishes, into air-breathing amphibians in the Devonian period. 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 universal tetrapod individuality of front limbs that bend backward at the elbow and hind limbs that bend onward at the knee can plausibly be traced to early tetrapods living in shallow water. www.rareresource.com /tetrapod.htm   (845 words)

Terrestrial Vertebrates Tetrapods originated no later than the Mississippian (about 350 million years ago), the period from which the oldest known relatives of living amphibians are known. Tetrapods range from 9.8 mm (in the frog Psyllophryne didactyla) to 30 m (in the blue whale) in overall length. A new primitive tetrapod, Whatcheeria deltae, from the Lower Carboniferous of Iowa. tolweb.org /tree?group=Terrestrial_Vertebrates&contgroup=Sarcopterygii   (3351 words)

Evolution: Library: Tetrapod Limbs The limbs of tetrapods all have the same pattern of bones. Darwin was one of the first to comment that it seems unlikely that this single skeletal structure could be the best one possible for each of the activities it is required to perform in different animals. The pentadactyl limbs that tetrapods far and wide all have are examples of homologous structures. www.pbs.org /wgbh/evolution/library/04/2/l_042_01.html   (498 words)

Fossil Record of the Tetrapods   (Site not responding. Last check: 2007-10-23) The early tetrapods were the first vertebrates to truly walk the land. The tetrapods began their conquest of land in the Paleozoic around 360 million years ago. Tetrapods are a name that we have given to anything with four feet (tetra=four, pod=feet). www.ucmp.berkeley.edu /vertebrates/tetrapods/tetrafr.html   (183 words)

Wikinfo | Tetrapod The primitive tetrapods developed from osteolopiform lobe-fin fishes, the Sarcopterygii— the 'living fossil' coelacanth is a lobe-finned fish— which had already developed some adaptations of fins with fleshy bases and bones, which they used as paddles in shallow water habitats choked with plants and detritus. The universal tetrapod characters 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. Today, most tetrapods are land-dwelling, at least in their adult forms, but some species, such as the axolotl remain aquatic. www.wikinfo.org /wiki.php?title=Tetrapod   (608 words)

Scientific American: Getting a Leg Up on Land   (Site not responding. Last check: 2007-10-23) Acanthostega showed that early tetrapods possessed a different dental plan: a small number of larger teeth on the outer row and a reduction in the size of the teeth populating the inner row--changes that probably accompanied a shift from feeding exclusively in the water to feeding on land or with the head above the water. The earliest tetrapods were all carnivorous, so it is unlikely that, as adults, they fed much on land during the first phases of their evolution, because the only prey they would have found there were insects and other small arthropods. For example, we know that tetrapods have lost all the bones that protect the gills in fish but that the genes that govern their formation are still present in mice, where they function differently. www.sciam.com /print_version.cfm?articleID=000DC8B8-EA15-137C-AA1583414B7F0000   (4360 words)

Evolution -- Tetrapod Transitionals She has devoted a good portion of a career working out the evolution of early tetrapods, the transitionals between fish and amphibians that later lead to the evolution of reptiles, birds and mammals. Clack tetrapod evolution consisted of three major events: the origin of limbs with digits, the origin of walking, and origin of terrestriality. Clack, J. The Neurocranium of Acanthostega gunnari and the Evolution of the Otic Region in Tetrapods. hometown.aol.com /darwinpage/tetrapods.htm   (1432 words)

Developmental Biology Online: Hox Genes and the Evolution of the Tetrapod Limb Hox Genes and the Evolution of the Tetrapod Limb Tetrapods and fishes share the first two phases of the Hox expression pattern in their appendages. Thus, while the Hox gene expression pattern is homologous between fish and tetrapod limbs in the proximal regions, the expression pattern in the late-bud distal mesenchyme is new. 7e.devbio.com /article.php?ch=16&id=251   (848 words)

The fossil record of ‘early’ tetrapods: evidence of a major evolutionary transition? According to evolutionary theory, the origin of tetrapods from a fish-like ancestor during the Devonian Period was one of the major events in the history of life on earth. The ‘earliest’ known tetrapods with feet and legs are now thought to have been aquatic animals; evolutionists therefore argue that feet and legs evolved in a shallow water environment and were only later co-opted for use on the land. Tetrapods were thought to have evolved during the Devonian, a period associated in many parts of the world with sediments stained red by iron oxide. www.answersingenesis.org /tj/v17/i2/tetrapod.asp?vPrint=1   (4959 words)

Tetrapod Fossil Found—First Ever in Asia   (Site not responding. Last check: 2007-10-23) Tetrapods are the first vertebrates with limbs—not fins—and the new find supports their link with lobe-finned fish. Tetrapods, Earth's oldest four-limbed creatures, walked along the ancient Chinese coastline as early as 355 million years ago, according to a fossilized jaw bone discovered and analyzed by an international team of scientists. Tetrapods are thought to have evolved from lobe-finned fish, such as lung fish and coelacanths. news.nationalgeographic.com /news/2002/12/1218_021218_tetrapod.html   (579 words)

Comment on "The Early Evolution of the Tetrapod Humerus" -- Ahlberg 305 (5691): 1715c -- Science GSM 104536, tetrapod humerus from the Late Devonian of Scotland. The Scat Craig humerus GSM 104536 was compared with those of the osteolepiform Eusthenopteron and the early and primitive tetrapods Ichthyostega, Acanthostega, Crassigyrinus, Proterogyrinus, Eoherpeton, and Greererpeton. The tetrapod humeri agree with respect to all the characters compared in the table, except (*) that an ectepicondylar foramen is absent in Proterogyrinus, Eoherpeton, and Greererpeton (I regard this character state as derived within the Tetrapoda). www.sciencemag.org /cgi/content/full/305/5691/1715c   (1147 words)

alb21-3 Tetrapod fossils are key to these correlations, and their organization into a global biochronology provides a time scale applicable to the nonmarine Triassic. The status of "provincial" tetrapod biochronology of the Triassic is that schemes exist for the Argentinian and Chinese record and for the Middle-Late Triassic record from North America. A mid-Permian to earliest Jurassic tetrapod biostratigraphy and its significance. www.biologie.uni-hamburg.de /b-online/kerp/Albart14.htm   (3493 words)

Brainstorms: Goodwin on tetrapod limbs "Tetrapod limbs are defined as the set of all possible forms generated by the rules of focal condensation, branching bifurcation, and segmentation in the morphogenetic field of the limb bud. If the particular limb structure of tetrapods isn't just one among many possible limb structures that natural selection could have hit upon, but instead is `in the cards', embryologically speaking, other features (like bipediality?) may also be less contingent than we think. My statement that homology of tetrapod limbs and common descent won't be rethought is simply an expression of a high level of confidence. www.iscid.org /boards/ubb-get_topic-f-6-t-000476.html   (2427 words)

The Epoch Times :: US Scientists Discover Fossil of Fish with Arms Shubin says it is from a tetrapod that lived in a freshwater stream about 370 million years ago before animals crawled on land. The first such tetrapod was discovered in 1987 in Greenland by British paleontologist Jennifer Clack of Cambridge University. He says the different kinds of tetrapod that lived nearly 400 million years ago had many features that have since disappeared, like more than five digits at the end of a limb. www.theepochtimes.com /news/4-4-9/20775.html   (764 words)

Tiktaalik - Wikipedia, the free encyclopedia Paleontologists suggest that it was an intermediate form between fish such as Panderichthys, which lived about 385 million years ago, and early tetrapods such as Acanthostega and Ichthyostega, which lived about 365 million years ago. Its mixture of fish and tetrapod characteristics led one of its discoverers, Neil Shubin, to characterize Tiktaalik as a "fishapod" 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. en.wikipedia.org /wiki/Tiktaalik   (913 words)

Darwin | American Museum of Natural History Tetrapods are vertebrates that have, or had, four limbs and include all amphibians, reptiles, birds and mammals. All tetrapod limbs are made up of similar sets of bones. Mammals are tetrapods with three middle ear bones instead of just one. www.amnh.org /exhibitions/darwin/evolution/homologies.php   (398 words)

Devonian Times - Tetrapod Trackways The identification of fossil footprints can be difficult, particularly in the case of early tetrapods, since knowledge of their foot anatomy is limited to three taxa (Acanthostega, Ichthyostega and Tulerpeton). On the other hand, the distorted tracks and drag marks in Trackway II suggest that the tetrapod’s body was not completely supported by water. The best-preserved pes impressions in Trackway I were 3.5 cm wide and the tetrapod that made these tracks is estimated to be 55 cm long. www.devoniantimes.org /Order/trackways.html   (1301 words)

Zimmer Chapter Two   (Site not responding. Last check: 2007-10-23) First tetrapod from N. America outside of Greenland -- and one of the oldest tetrapods known. Tetrapod and fish expertise brought to bear on the study. Limb structure intermediate between tetrapod (proximal) and lobe-fin (distal). www.ucalgary.ca /~zoology/Zool571/ch2.htm   (1378 words)

hunt During the same timeframe there was a major reevaluation of the equally confused ichnotaxonomy of tetrapod tracks from Permian eolianites (Morales and Haubold, 1995; Haubold et al., 1995a, b; McKeever and Haubold, 1996; Haubold, 1996; Hunt and Santucci, 1998a,b). Tetrapod ichnofacies have been defined as "multiple ichnocoenoses that are similar in ichnotaxonomic composition and show recurrent association in particular environments (Lockley et al., 1994, p. Tetrapod ichnofacies in Early Permian red beds of the American Southwest: New Mexico Museum of Natural History and Science Bulletin, v. www2.nature.nps.gov /geology/paleontology/pub/fossil_conference_6/hunt.htm   (2172 words)

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