When Dr. Flammang and her colleagues analyzed the images, they confirmed their initial hunch: The fish were using their tetrapod-like bodies to walk with a tetrapod-like gait.
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But the oldest tetrapod fossils found so far date only to 375 million years.
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But the fossil of this tetrapod held another surprise: it likely never left the water.
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The result is "the first life history of a Devonian tetrapod species," according to the authors.
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Other fish can move on land, although none of them use a tetrapod gait to do so.
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In many ways, the skeleton of the fish looked like what you'd see on a walking tetrapod.
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"Acanthostega does not seem to be the only stem tetrapod with a long juvenile stage," Sanchez told me.
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Instead of flopping or crutching, the cave fish were using what looked like a full-blown tetrapod gait.
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At the time, they only found a portion of the skull's roof and assumed it was a tetrapod.
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The newly discovered example was an early tetrapod, which maintained characteristics similar to fish in some of its bones.
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This tetrapod, dubbed Parmastega aelidae, looked similar to a crocodile, except its protruding eyes were on top of its head.
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Scientists have not found fossils of the snake family's four-legged ancestors, though they are certain these tetrapod forebears existed.
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Like other similar fish, Elpistostege's fin also has the precursors of tetrapod limb bones including the upper arm, forearm and wrist.
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Scientists have found trackways in Poland dating back almost 400 million years that look as if they were made by a walking tetrapod.
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It's possible that a fish, rather than a primitive tetrapod, made those tracks by moving as the waterfall-climbing cave fish does today.
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This discovery suggested that Hoxa-13 and Hoxd-13 genes tell certain cells in the tetrapod limb bud that they will develop into hands and feet.
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Researchers have focused their efforts on tetrapod-like fish, called elpistostegalians, that lived between 359 and 393 million years ago during the Middle and Late Devonian periods.
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In other words, polycephaly is a well-documented bug in tetrapod DNA, and sharks are one of many lifeforms that have to live and die with it.
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Animals had just begun pulling themselves out of the water and exploring the big, dry world, and here was the plant-eating tetrapod Orobates, making its way on four legs.
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GIF: Jonas Lauströer (HAW Hamburg), Amir Andikfar (HAW Hamburg), John Nyakatura (HU Berlin)/GizmodoThe model for their experiment was an early four-legged, 35-inch-long tetrapod known as Orobates pabsti.
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"I strongly think that knowing more about the life-history traits of other stem tetrapods will help us build up a more accurate theory on the tetrapod move to land," she said.
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Researchers believe its eyes were above water while the rest of its body lurked below because there are lines in the skull where sensory organs once helped the tetrapod sense vibrations in the water.
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While most fish have simple pelvic bones to control their fins, CT scans reveal that the Cryptotora thamicola actually has a developed pelvis which resembles that of a tetrapod, like a cow or horse.
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As they report in Nature Ecology and Evolution, Dr Clack and her colleagues have identified and named five hitherto-unknown species of tetrapod from the gap, and gathered material from seven other, as-yet-unnamed ones.
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Given that we owe our very existence to this bold move, scientists have long been fascinated by how our tetrapod ancestors pushed out of the sea to become "part of that world," to channel The Little Mermaid.
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A team led by Sophie Sanchez, an evolutionary biologist based at Uppsala University in Sweden, studied the remains of at least 20 individuals from the early Acanthostega tetrapod clan, preserved in what scientists called a "mass-death deposit," discovered in Greenland.
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"Today we announce in the journal Nature our discovery of a complete specimen of a tetrapod-like fish, called Elpistostege, which reveals extraordinary new information about the evolution of the vertebrate hand," said John Long, study author and Strategic Professor in Palaeontology at Flinders University in Australia.
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The group so defined is known as the tetrapod total group. Stegocephalia is a larger group equivalent to some broader uses of the word tetrapod, used by scientists who prefer to reserve tetrapod for the crown group (based on the nearest common ancestor of living forms). Such scientists use the term "stem-tetrapod" to refer to those tetrapod-like vertebrates that are not members of the crown group, including the tetrapodomorph fishes. The two subclades of crown tetrapods are Batrachomorpha and Reptiliomorpha.
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It is the largest predatory tetrapod known from Triassic Scotland.
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Book Review: Sea Monsters on Medieval and Renaissance Maps. Tetrapod Zoology.
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Macrofloral and palynological information help date them. Ireland hosts late Middle Devonian tetrapod trackways at three sites on Valentia Island within the Valentia Slate Formation.Stössel, I. 1995. The discovery of a new Devonian tetrapod trackway in SW Ireland.
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Similar concrete objects like Dolos are A-jack, Akmon, Xbloc, Tetrapod and Accropode.
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The African coelacanth genome provides insights into tetrapod evolution. Nature 496:311-316.
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Doragnathus is an extinct genus of tetrapod from the Early Carboniferous of Scotland.
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However, there are issues with supposing that Tiktaalik is a tetrapod ancestor. For example, Tiktaalik had a long spine with far more vertebrae than any known tetrapod or other tetrapodomorph fish. Also the oldest tetrapod trace fossils (tracks and trackways) predate Tiktaalik by a considerable margin. Several hypotheses have been proposed to explain this date discrepancy: 1) The nearest common ancestor of tetrapods and Tiktaalik dates to the Early Devonian.
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In recent decades, numerous tetrapod fossils dating from the earliest Carboniferous have been found.
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Crassigyrinus (meaning "thick tadpole") is an extinct genus of carnivorous stem tetrapod from the Early Carboniferous Limestone Coal Group of Scotland and possibly Greer, West Virginia.Godfrey, S. J. 1988. Isolated tetrapod remains from the Carboniferous of West Virginia. Kirtlandia 43, 27-36.
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Naish, D. (2007). Feathers and Filaments of Dinosaurs, Part II Tetrapod Zoology, April 23, 2011.
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Trackways of tetrapod vertebrates from the Upper Devonian of Victoria, Aust. Nature 238, 469-470.
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It was not until 2002 that Jennifer Clack named and reclassified the fossil as a primitive tetrapod. Pederpes is placed in the family Whatcheeriidae, of uncertain relationships to other tetrapod families. While an amphibian in the broad sense, under cladistic taxonomy, Pederpes is not a member of the crown group amphibian in the meaning of modern amphibians. As a very basal (primitive) tetrapod, it falls under the traditional class Amphibia in Linnaean taxonomy.
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Tetrapod Spools was an Encinitas, California, USA based independent record label founded in Oak Park, Illinois in 1969 by Louie Easley Hanley and Mark Tucker. The label originally released music on reel-to-reel and cassette, later producing limited edition vinyl records. The best known release on Tetrapod Spools is undoubtedly Tucker's 1975 album "Batstew" which has achieved cult status and become a highly sought-after collectible. Tetrapod Spools relocated to Encinitas, California in 1980.
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In the tetrapod, the front of the skull lengthened, positioning the orbits farther back on the skull.
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Sinostega is an extinct genus of early "tetrapod" from the Late Devonian of China. The fossil was discovered in the Ningxia Hui Autonomous Region, northwest China, and consist of a fragmentary lower jawbone measuring 7 cm in length. It is the first Devonian tetrapod to be found in Asia.
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Carnivorous dinocephalian from the Middle Permian of Brazil and tetrapod dispersal in Pangaea. PNAS, 109 (5): 1584-1588.
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Their result also placed the recently discovered stem-tetrapod Aytonerpeton within Adelospondyli as the sister taxon to Acherontiscus.
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385 Mya (Valentia Island, Ireland).Stossel, I. (1995) The discovery of a new Devonian tetrapod trackway in SW Ireland. Journal of the Geological Society, London, 152, 407-413.Stossel, I., Williams, E.A. & Higgs, K.T. (2016) Ichnology and depositional environment of the Middle Devonian Valentia Island tetrapod trackways, south-west Ireland.
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The Colosteidae are a family of stegocephalians (tetrapod-like vertebrates) that lived in the Carboniferous period. They possessed a variety of characteristics from different tetrapod or stem-tetrapod groups, which made them historically difficult to classify. They are now considered to be part of a lineage intermediate between the earliest Devonian terrestrial vertebrates (such as Ichthyostega), and the different groups ancestral to all modern tetrapods, such as temnospondyls (possibly ancestral to modern amphibians) and reptiliomorphs (ancestral to amniotes such as mammals, reptiles, and birds).
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Lastly, the braincase of Panderichthys demonstrates a key intermediate within the fish-evolution sequence. From the outside, Panderichthys has a tetrapod-like head, but actually retains an intracranial joint that is a characteristic of fish. Panderichthys shares many features with the osteolepiform Eusthenopteron such as similar hyomandibular and basipterygoid processes. Even though its head is shaped similar to that of a tetrapod, tetrapod craniums lack a lateral commissure, jugular groove, basicranial fenestra, arcual plate, and intracranial joint, all of which are present in Panderichthys.
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Kraterokheirodon ("cupped hand tooth") is an extinct genus of enigmatic tetrapod from the Late Triassic Chinle Formation of Arizona. The type and only species is K. colberti. Although it is known only from two large teeth, their shape is so unlike those of any other animal that Kraterokheirodon cannot definitively be classified under any known group of tetrapods. Its discovery also indicates that our understanding of Late Triassic tetrapod diversity is still incomplete, with Kraterokheirodon representing an otherwise unknown lineage of large tetrapod in western North America.
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Romer's gap, which spans most of the Mississippian age of the Carboniferous, is characterized by a comparative rarity of tetrapod and stem- tetrapod fossils compared to the periods of time directly older and younger than it. However, Aytonerpeton and other Ballagan stem-tetrapods help to close in this gap in the vertebrate fossil record.
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Apart from numerous invertebrates, a prominent vertebrate fauna is also known from the Bickett Shale of the Bluefield Formation at Greer. Preserved vertebrate fossils include acanthodians, lungfish, rhizodonts, and articulated tetrapod remains. Several new tetrapod genera have been named from Greer: Greererpeton (a colosteid), Proterogyrinus (a basal embolomere), and Mauchchunkia (a synonym of Proterogyrinus).
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Popular subjects commonly written about include frogs, reptiles, mammals, birds, dinosaurs, pterosaurs, and cryptozoology. Together with colleagues Michael P. Taylor and Mathew Wedel, Naish also contributes to the Sauropod Vertebra Picture of the Week blog. In 2010, Naish published a collection of early articles from Tetrapod Zoology as a book titled Tetrapod Zoology Book One.
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The Tetrapod Zoology Podcast was launched on 1 February 2013 and is the official podcast of the TetZooVerse. The podcast covers all things tetrapod and vertebrate palaeontology. The podcast is hosted by Naish and co-host John Conway, For episode 15 the regular hosts were joined by Memo Kosemen, co-author and artist of Cryptozoologicon.
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All known forms of Frasnian tetrapods became extinct in the Late Devonian extinction, also known as the end-Frasnian extinction. This marked the beginning of a gap in the tetrapod fossil record known as the Famennian gap, occupying roughly the first half of the Famennian stage. The oldest near-complete tetrapod fossils, Acanthostega and Ichthyostega, date from the second half of the Fammennian. Although both were essentially four- footed fish, Ichthyostega is the earliest known tetrapod that may have had the ability to pull itself onto land and drag itself forward with its forelimbs.
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So, for example, the tetrapod splenial developed a medially-directed twist of the ventral margin, exposing the splenial ventrally and mesially.
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The dermal skull roof of Acanthostega gunnari, an early tetrapod from the Late Devonian. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 93(01), 17-33. Large coronoid fangs are present in the fishes Eusthenopteron, Panderichthys, and Tiktaalik, and the early tetrapod, Ventasega. In Acanthostega, which is more derived, the large teeth are absent.
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Clack, J. A. (2002) Gaining Ground. Indiana University The fins of lobe-finned fish differ from those of all other fish in that each is borne on a fleshy, lobelike, scaly stalk extending from the body. Pectoral and pelvic fins have articulations resembling those of tetrapod limbs. These fins evolved into legs of the first tetrapod land vertebrates, amphibians.
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Schoch, R. R. 2011. A procolophonid-like tetrapod from the German Middle Triassic. Neues Jahrbuch fur Geologie und Palaontologie, Abhandlungen 259:251–255.
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With a short, wide skull, large eyes, and strongly-built limbs, Eucritta proportionally resembled Balanerpeton, a contemporary terrestrial tetrapod which was one of the earliest members of Temnospondyli, a successful tetrapod group which may have produced modern amphibians. However, Eucritta lacked key temnospondyl adaptations, nor certain adaptations of reptiliomorphs (the tetrapod lineage that would lead to reptiles and other amniotes). In other cases, it possesses certain characteristics in common with each. Its closest relatives may have been baphetids such as Megalocephalus, based on the possession of slight embayments on the front edge of the eye sockets.
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Thomas Huxley examined the idea and argued against it. He suggested that the tetrapod limb or cheiropterygium differed in its origins from that of the lungfish and that the two may have diversified from a true ancestral archipterygium. An alternate origin for tetrapod limbs was identified in the lateral fins by Francis Balfour. These were followed by several other modified hypotheses.
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Some localities are well known for their abundance of tetrapod fossils. Theraspids include the kannemeyeriid Dinodontosaurus, and cynodonts such as Probainognathus and Massetognathus, the latter being the most abundant tetrapod taxon in the formation represented by Massetognathus pascuali and M. teruggii.Romer, 1967, III Other notable tetrapods present from the formation are the archosaurs. Ornithodirans include Lewisuchus,Romer, 1972, XIVBittencourt, 2014, p.
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Map of Okinotorishima is a coral reef with two rocks enlarged with tetrapod- cement structures. It is administered by Japan with a total shoal area of and land area . Its dry land area is mostly made up by three concrete encasings and there is a stilt platform in the lagoon housing a research station. There is a third complete artificial tetrapod-cement islet.
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The tetrapod groups that are hypothesized as ancestors of modern amphibians (lepospondyls and amphibamid temnospondyls) appear in the Late Carboniferous, roughly 300 million years ago. Large fossil tetrapod assemblages are known from the Artinskian stage of the Early Permian about 275 million years ago and contain no lissamphibians, suggesting that the Early Permian may be an upper bound for the age of Batrachia.
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In the south-east of the basin lies the Rewan Formation. Small assemblages of the tetrapod species, Lydekkerina from the Lootsbergian age, have been found.
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Jakubsonia is an extinct genus of early tetrapod from the Late Devonian of Russia. The type species, Jakubsonia livnensis, was described and named in 2004.
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During the Early Permian the center of tetrapod diversity was in the equatorial regions of the supercontinent Pangea, and Timonya was part of this fauna.
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The order Chiroptera, comprising all bats, has evolved the unique mammalian adaptation of flight. Bat wings are modified tetrapod forelimbs. Because bats are mammals, the skeletal structures in their wings are morphologically homologous to the skeletal components found in other tetrapod forelimbs. Through adaptive evolution these structures in bats have undergone many morphological changes, such as webbed digits, elongation of the forelimb, and reduction in bone thickness.
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The morphology of tetrapodomorphs, fish that are similar- looking to tetrapods, give indications of the transition from water to terrestrial life. Pectoral and pelvic fins have articulations resembling those of tetrapod limbs. The first tetrapod land vertebrates, basal amphibian organisms, possessed legs derived from these fins. Sarcopterygians also possess two dorsal fins with separate bases, as opposed to the single dorsal fin of actinopterygians (ray-finned fish).
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Peter John Barrett (born 11 August 1940) is a New Zealand geologist who came to prominence after discovering the first tetrapod fossils in Antarctica in 1967.
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They also imply that a very long ghost lineage of whatcheeriids lived through Romer's gap, a period during the Early Carboniferous conspicuously lacking in tetrapod remains.
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24 Tetrapod ichnofossils, probably belonging to a chirotherian (and possibly an archosaur), were discovered in the formation southeast of Pagancillo by Argentina paleontologist José Bonaparte in 1964.
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It differs from all other tetrapod cleithra in the presence of a projecting posterior flange, with striated texture and a jagged margin, on the middle part of the blade.
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Their fins are fleshy, lobed, paired fins, joined to the body by a single bone. The fins of lobe-finned fish differ from those of all other fish in that each is borne on a fleshy, lobelike, scaly stalk extending from the body. The pectoral and pelvic fins are articulated in ways resembling the tetrapod limbs they were the precursors to. The fins evolved into the legs of the first tetrapod land vertebrates, amphibians.
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The adaptation may also be interpreted as a specialization for buccopharyngeal breathing. It is speculated to be the first step towards aerial respiration in the transition from fish to tetrapod.
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The Schistosomatoidea are a superfamily of digenetic trematodes.Snyder, S. D. (2004). Phylogeny and paraphyly among tetrapod blood flukes (Digenea: Schistosomatidae and Spirorchiidae). International Journal for Parasitology 34(12), 1385-92.
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Klein, H. & Lucas, S. G. 2013. The Late Triassic tetrapod ichnotaxon Apatopus lineatus (Bock, 1952) and its distribution. Bulletin of the New Mexico Museum of Natural History 61, 313-324.
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J. Geol. Soc. Lond. 152, 407–413.Stössel, I, Williams, E.A. & Higgs, K.T. 2016. Ichnology and depositional environment of the Middle Devonian Valentia Island tetrapod trackways, south-west Ireland. Palaeogeog.
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Pederpes is the earliest-known tetrapod to show the beginnings of terrestrial locomotion and despite the probable presence of a sixth digit on the forelimbs it was at least functionally pentadactyl.
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The 'Brule Forest' is the only example of standing trees, or in-situ tree-trunks of Walchia. Four-footed, tetrapod animal fossil trackways are also found in the fossil rich rocks.
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In 2016 it was reported that the waterfall climbing cave fish walks with a tetrapod-like diagonal-couplets lateral sequence gait, displaying a robust pelvic girdle attached to the vertebral column.
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Restoration of Acanthostega In the tetrapod and higher clades from the lower-middle Famennian there are several defining changes on the basis of anatomy of Ichthyostega, Tulerpeton, and Acanthostega. In the cranium, there is a stapes derived from the hyomandibular of fishes; a single bilateral pair of nasal bones, and a fenestra ovalis in the otic capsule of the braincase.Lebedev, O. A., & Coates, M. I. (1995). The postcranial skeleton of the Devonian tetrapod Tulerpeton curtum Lebedev.
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Fossil ferns and horsetails have also been found. Rhynchosaurs and cynodonts (especially rhynchosaur Hyperodapedon and cynodont Exaeretodon) are by far the predominant findings among the tetrapod fossils in the park. A study from 1993 found dinosaur specimens to comprise only 6% of the total tetrapod sample; subsequent discoveries increased this number to approximately 11% of all findings. Carnivorous dinosaurs are the most common terrestrial carnivores of the Ischigualasto Formation, with herrerasaurids comprising 72% of all recovered terrestrial carnivores.
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Naish with Matt Wedel and Mike P. Taylor, the three writers of SVPOW TetZooCon 2015, London Wetland Centre In 2006, Naish started a weblog, Tetrapod Zoology, that covered various aspects of zoology. In 2007 he joined the ScienceBlogs network. In July 2011, the blog moved to the Scientific American blog network, as of 31 July 2018 the blog has moved away from Scientific American and is hosted independently. Tetrapod Zoology seems to cover most subjects concerning tetrapods.
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Closer to the trail and lower in the sequence is the Blue Beach Member and further along is the Hurd Creek Member. Blue Beach is the type locality for the apparent gap in the tetrapod fossil record known as Romer's gap. Sir William Logan, the first Director of the Geological Survey of Canada, found footprints from a tetrapod in 1841. It remains one of very few such outcrops in the world; the others are in Scotland.
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There are multiple configurations for tetrapod gaits, but the legs that swing together must be on contralateral sides of the body . Tetrapod gaits are typically used at medium speeds and are also very stable. A walking gait is considered tripod if three of the legs enter the swing phase simultaneously, while the other three legs make contact with the ground. The middle leg of one side swings with the hind and front legs on the contralateral side .
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Examination of phylogenetic frameworks of tooth and jaw morphologes has revealed that dental occlusion developed independently in several lineages tetrapod herbivores. This suggests that evolution and spread occurred simultaneously within various lineages.
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For a comprehensive bibliography of the bioerosion literature, please see the External links below. Cast of a tridactyl footprint of theropod dinosaur "Eubrontes" from the Triassic of the Czech Republic The oldest types of tetrapod tail-and-footprints date back to the latter Devonian period. These vertebrate impressions have been found in Ireland, Scotland, Pennsylvania, and Australia. A sandstone slab containing the track of tetrapod, dated to 400 million years, is amongst the oldest evidence of a vertebrate walking on land.
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Antlerpeton is an extinct genus of early tetrapod from the Early Carboniferous of Nevada. It is known from a single poorly preserved skeleton from the Diamond Peak Formation of Eureka County. A mix of features in its compound vertebrae suggest that Antlerpeton is a primitive stem tetrapod that has affinities with later, more advanced forms. Its robust pelvis and hind limbs allowed for effective locomotion on land, but the animal was likely still tied to a semiaquatic lifestyle near the coast.
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Occidens is an extinct genus of stem tetrapod that lived during the earliest part of the Carboniferous in what is now Northern Ireland. It is known from a single type species, Occidens portlocki, named in 2004 on the basis of a left lower jaw that British geologist Joseph Ellison Portlock described in 1843. Portlock attributed it to the lobe-finned fish Holoptychius and it was housed in the collections of the British Geological Survey for over a century before being reevaluated in 2004 by vertebrate paleontologists Jenny Clack and Per E. Ahlberg, who reclassified it as a new genus and species of early tetrapod. The genus name Occidens refers to its presence west of better-known early tetrapod assemblages in Great Britain, and the species name honors Portlock.
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Phylogeny and paraphyly among tetrapod blood flukes (Digenea: Schistosomatidae and Spirorchiidae). International Journal for Parasitology 34(12), 1385-92. It has been synonymised with Proparorchiidae Ward, 1921, Spirorchidae Stunkard, 1921, and Spirorchiidae MacCallum, 1921.
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Tetrapod fossils have been identified in the type section of the Youngsville Member. These include coprolites and indeterminate metoposaurid and phytosaur remains, including a paramedian scute that may be the aetosaur Longosuchus or Desmatosuchus.
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Laurin, M. (1998, March). The importance of global parsimony and historical bias in understanding tetrapod evolution. Part I. Systematics, middle ear evolution and jaw suspension. In Annales des Sciences Naturelles- Zoologie et Biologie Animale (Vol.
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Pardo and Mann (2018) demonstrated that H. longidentatum belongs to the limbless tetrapod clade Aistopoda and renamed it Andersonerpeton in honor of Jason S. Anderson, a contributor to enhanced understanding of aïstopod morphology and phylogeny.
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2005b The microfossils date the Yeso Group to the Kungurian.Vachard et al. 2014 Tetrapod trackways have been found in the De Chelly Sandstone in the Lucero uplift. These are too poorly preserved for precise classification.
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Based on the morphology of both cranial and post-cranial elements discovered (see below), Ventastega is more primitive than other Devonian tetrapodomorphs including Acanthostega and Ichthyostega, and helps further understanding of the fish-tetrapod transition.
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In 2013, the Atlantic Geoscience Society granted Reid the Laing Ferguson Distinguished Service Award, and in 2016 Reid was inducted into the Order of Nova Scotia. In 2015, researchers announced that a new ichnofossil - a tetrapod trackway found in several formations of the Cumberland Group including the Joggins Formation - would be named in honour of Reid when the species was formally described. The trackway consists of footprints 10 cm (3.9 in) wide, and likely represent the Joggins Formation's largest tetrapod and top predator (possibly Baphetes).
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Ossinodus is an extinct genus of stem tetrapod. Fossils have been found from the Ducabrook Formation in Queensland, Australia dating back to the middle Visean stage of the Early Carboniferous (Mississippian). It was originally placed within the family Whatcheeriidae, but the absence of an intertemporal bone as suggested by a recent reconstruction of the skull based on fragmentary material may prove it to be stemward of all whatcheeriids. The oldest known pathological bone of a tetrapod, a fractured right radius, has been referred to Ossinodus.
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Restoration showing side to side undulation Additionally, the pelvic girdle and pelvic fins of Panderichthys represents an intermediate in the fish-tetrapod evolution. During the fish-tetrapod evolution the pelvic girdle became a weight bearing structure when the ilium, meso-ventral contact of the sides of the girdle, an ilium, and a sacral rib developed. The femur and humerus became longer and the radius/ulna and tibia/fibula became more equal in length. In general, the pelvic girdle in Panderichthys is more primitive than the pectoral girdle.
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Although the words quadruped and tetrapod are both derived from terms meaning "four-footed", they have distinct meanings. A tetrapod is any member of the taxonomic unit Tetrapoda (which is defined by descent from a specific four-limbed ancestor) whereas a quadruped actually uses four limbs for locomotion. Not all tetrapods are quadrupeds and not all quadrupeds are tetrapods. The distinction between quadrupeds and tetrapods is important in evolutionary biology, particularly in the context of tetrapods whose limbs have adapted to other roles (e.g.
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The presence of Sungeodon in the earliest Triassic Jiucaiyuan Formation indicates that dicynodonts diversified soon after the Permian- Triassic extinction event, mirroring the explosive radiations of other tetrapod groups such as archosaurs soon after the extinction.
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Greer is an unincorporated community in Mason County, West Virginia. The community derives its name from the local Greer Limestone Company. The Mississippian tetrapod Greererpeton burkemorani was named after this community by Alfred Romer in 1969.
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Tetrapod Zoology. 18 January 2008. Accessed 31 January 2008 (). It was not until 2011 that T. navigans was formally reclassified in the genus Tupandactylus, in a subsequent study supporting the conclusions of Unwin and Martill in 2007.
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Some basic fossil trackway types: :#footprints :#tail drags :#belly drag marks - (e.g., tetrapods)Stössel, I, Williams, E.A. & Higgs, K.T. 2016. Ichnology and depositional environment of the Middle Devonian Valentia Island tetrapod trackways, south-west Ireland. Palaeogeog., Palaeoclimatol.
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For example, Robert McNeill Alexander, one of the pioneers of modern biomechanics, used it in his plenary lecture on optimization in evolution in 2008.Professor Alexander on the Turtles and the Gömböc. Tetrapod Zoology (24 May 2008).
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Review of the tetrapod fauna of the "Lower Stormberg Group" of the main Karoo Basin (southern Africa): Implication for the age of the Lower Elliot Formation. Bulletin de la Société Géologique de France. 175(1), 73-83.
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Tetrapod Zoology : Bipedal orangs, gait of a dinosaur, and new- look Ichthyostega: exciting times in functional anatomy part I Oliver reverted to knuckle-walking after developing arthritis. Non-human primates often use bipedal locomotion when carrying food.
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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", which now covers the period from about 360 to 345 million years ago (the Devonian-Carboniferous transition and the early Mississippian), after the palaeontologist who recognized it. 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.
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The structure of the plants show no adaptation toward cold tolerance, suggesting that the climate was much warmer in the Triassic. The Fremouw Formation preserves many tetrapod fossils that span the Permo-Triassic boundary, which marks the Permo-Triassic mass extinction. Around the world, the fossil record of many tetrapod groups is absent or very limited in Early Triassic rocks, implying a major decline in diversity after the extinction. The presence of many of these groups in Middle Triassic strata indicate that long ghost lineages must have extended back into the Early Triassic.
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Eucritta (meaning "true creature") is an extinct genus of stem-tetrapod from the Viséan epoch in the Carboniferous period of Scotland. The name of the type and only species, E. melanolimnetes ("true creature from the black lagoon") is a homage to the 1954 horror film Creature from the Black Lagoon. Eucritta possessed many features in common with other generalized Carboniferous tetrapods and tetrapod relatives. A large amount of these features were plesiomorphic, meaning that they resembled the "primitive" condition that was acquired when four-limbed vertebrates ("amphibians", in the broad sense) first appeared.
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The pelvic (hip) girdle was fairly typical by early tetrapod and stem-tetrapod standards, with a two-pronged ilium, a plate-like ischium, and no bony pubis. The leg bones were rectangular and the five-toed feet had a phalangeal formula (number of joints per toe) of 2-3-4-5-?. None of the specimens preserve a complete vertebral column, but based on the number of ribs the body was probably rather short and squat. The dorsal (trunk) ribs themselves were only slightly curved and shorter and more tapering near the pelvic area.
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This is due to the humerus of Panderichthys being a shape that is more of an intermediate, while the femur is more primitive because of the length ratio to the fibula and that it lacks an adductor blade and crest. This implies that Panderichthys was not capable of tetrapod-like hindlimb propelled locomotion because of its small pelvic fins, non-weight bearing pelvic girdle, acetebelum oriented posteriorly, and limited knee and elbow flexion.Boisvert, Catherine A. "The pelvic fin and girdle of Panderichthys and the origin of tetrapod locomotion." Nature 438.7071 (2005): 1145-1147.
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What this means is that there was no major change of the braincase construction since the first sarcopterygian, but instead there had been only changes in skull shape. This implies that the evolution of the braincase during the transition from fish-tetrapod was very rapid and seems to display the same timing as the evolution of the pelvic girdle. In general, Panderichthys demonstrates that the braincase structure evolved much more slowly than the external skull morphology that created the tetrapod-like appearance of the head.Ahlberg, Per E., Jennifer A. Clack, and Ervīns Luk&sbreve.
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Nine tetrapod trackways from three sites have been reported from the Valentia Slate Formation of Valentia Island, Ireland. The Valentia Slate Formation is composed mostly of purple coloured fine-grained sandstones and siltstones interpreted to represent a fluvial setting. The trackways are late Middle Devonian in age based on a palynological assemblage from the Valentia Slate Formation and the U-Pb radioisotopic dating of an interstratified air-fall tuff bed to ca. 385 Ma, making these tetrapod trackways some of the earliest recorded, along with traces of early Middle Devonian (Eifelian) age from Poland.
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Tiktaalik lived approximately 375 million years ago. Paleontologists suggest that it is representative of the transition between non-tetrapod vertebrates such as Panderichthys, known from fossils 380 million years old, and early tetrapods such as Acanthostega and Ichthyostega, known from fossils about 365 million years old. Its mixture of primitive fish and derived tetrapod characteristics led one of its discoverers, Neil Shubin, to characterize Tiktaalik as a "fishapod." Unlike many previous, more fish-like transitional fossils, the "fins" of Tiktaalik have basic wrist bones and simple rays reminiscent of fingers.
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Parmastega is an extinct genus of tetrapod from the Devonian, dated to the earliest Famennian age (about 372 million years ago), in contrast to later fossils known from late Famennian (365–359 million years ago). These later fossils are considerably younger, by about 30 million years, than the earliest recorded tetrapod footprints, which presented a mystery that Parmastega's more recently described morphology from a three dimensional reconstruction has helped provide light on. One remaining mystery is what exactly it hunted. There were large invertebrates on land but they were not necessarily common.
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Bulletin of the American Museum of Natural History 88:53-96. A 1998 study again found Leptosuchus to be congeneric with Rutiodon,Lucas, S. G. (1998). Global Triassic tetrapod biostratigraphy and biochronology. Palaeogeography, Palaeoclimatology, Palaeoecology 143:347-384.
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Museum of Northern Arizona, Flagstaff, AZ. Bulletin 59. freshwater bivalves, freshwater mussels and snails, and ostracods.Lucas, S. G., and Tanner L. H. 2007. Tetrapod biostratigraphy and biochronology of the Triassic-Jurassic transition on the southern Colorado Plateau, USA.
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Gess, Robert W.; Whitfield, Alan K. (August 22, 2020). "Estuarine fish and tetrapod evolution: insights from a Late Devonian (Famennian) Gondwanan estuarine lake and a southern African Holocene equivalent". Biological Reviews. 95 (4): 865–888. doi:10.1111/brv.
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It has been suggested that ganoine is homologous to tooth enamel in vertebrates or even considered a type of enamel. Ganoine indeed contains amelogenin-like proteins and has a mineral content similar to that of tetrapod tooth enamel.
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In Feeding: Form, function and evolution in tetrapod vertebrates (pp. 175-291). Elsevier. Chemoreception further allows them to detect food odours through the Vomeronasal System (Jacobsen's organ), olfactory system through the nasal cavity and gustation by the tongue's surface.
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Ventastega has helped further research on the Fish- Tetrapod transition, the event during the Devonian when digit bearing tetrapods evolved from finned, fish ancestors. Research on rates of character changes in tetrapods have shown that there were high rates of character changes in the Devonian, which led to the conflicting hypotheses of either the tetrapods had few major changes that occurred during the Devonian or had many small but rapid morphology changes. The braincase of Ventastega has a mixture of fish-like and tetrapod-like characteristics, indicating that changes in the braincase during the fish-tetrapod transition occurred through a series of many small changes instead of one large change. The skull morphology of Ventastega has helped informed the hypothesis that changes in skull roof pattern proportions also occurred gradually, with the snout elongating and eyes increasing in size while moving dorsally over time.
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Angielczyk, Kenneth D., and Melony L. Walsh. "Patterns in the evolution of nares size and secondary palate length in anomodont therapsids (Synapsida): implications for hypoxia as a cause of end- Permian tetrapod extinctions." Journal of Paleontology 82.3 (2008): 528-542.
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Ruta, M.; Coates, M.I. & Quicke, D.L.J. (2003): Early tetrapod relationships revisited. Biological Reviews no 78: pp 251-345.PDF Members of Westlothiana were heavily scaled, with thin scales on the belly and many rows of thick, overlapping scales on the back.
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Hispaniachelys is known from postcranial material. It is the only known tetrapod from the Mesozoic of the Prebetic and the oldest turtle from southern Europe, dating to the late Oxfordian of the early Late Jurassic, about 161.2-158 million years ago.
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Eileanchelys existed in the Kilmaluag Formation of the Great Estuarine Group. This formation has an abundance of tetrapod fauna, including salamanders; the choristodere Cteniogenys sp.; crocodilians; the lepidosauromorph Marmoretta sp.; various lizards; pterosaurs; dinosaurs; the synapsid Stereognathus hebridicus; and early mammals.
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Another field of methods is the experimental work done with foot models or severed limbs.Milan, J., & Bromley, R. (2006). True tracks, undertracks and eroded tracks, experimental work with tetrapod tracks in laboratory and field. Palaeogeography, Palaeoclimatology, Palaeoecology ( 231), S. 253-264.
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It represents one of the geologically youngest known long-snouted trematosaurs and the first record of these temnospondyls from the Late Triassic of North America. It is also the oldest known tetrapod fossil from the Triassic of the Newark basin.
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Diagram showing different types of tetrapod vertebrae, with rhachitomes in blue area at left. The Rachitomi were a group of extinct Palaeozoic labyrinthodont amphibians, according to an earlier classification system.Kent, G.C. & Miller, L. (1997): Comparative anatomy of the vertebrates. 8th edition.
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Pederpes, a tetrapod from the Early Carboniferous period, also has hindlimbs containing 5 digits that are rotated to face anteriorly. Unlike previous tetrapods, who have been only partially adapted to land, Pederpes has the novel ability to bend its limbs and propel itself forwards in a terrestrial setting. This is attributed to the symmetry of the digits and limbs in Pederpes, allowing it to rotate its hindlimbs to an anteriorly facing position and propel itself from the edge of the foot when moving forward. This morphological development of bendable wrists and ankles can distinguish Pederpes the first true terrestrial tetrapod.
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However, in 2008, Bolt and his colleague Marcello Ruta published a phylogenetic analysis that did include Sigournea, and found good support for S. multidentata grouping with Occidens portlocki, a species of stem tetrapod named in 2004 from the earliest Carboniferous (Tournaisian) of Northern Ireland. Milner et al. (2009) suggested that Sigournea may be a close relative of the slightly younger baphetoid tetrapod Spathicephalus from Scotland and Nova Scotia based on the presence of small, closely packed marginal teeth in both taxa. However, their proposition was tentative because they did not include Sigournea in their phylogenetic analysis.
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Calligenethlon is an extinct genus of embolomere reptiliomorph from the Late Carboniferous of Joggins, Nova Scotia. It is the only definitively identified embolomere from the Joggins Fossil Cliffs and is the largest tetrapod to have been found preserved in lycopod tree stumps.
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In: W.F. Perrin, B. Wursig and J.G.M. Thewissen (eds), Encyclopedia of Marine Mammals Academic Press. pp. 552–560. Harbor seals have been recorded to attack, kill and eat several kinds of ducks."Harbour seal kills and eats duck", Tetrapod Zoology, 6 march 2008.
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In 2004, an expedition to islands in the Canadian arctic searching specifically for this fossil form in rocks that were 375 million years old discovered fossils of Tiktaalik. Some years later, however, scientists in Poland found evidence of fossilised tetrapod tracks predating Tiktaalik.
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While the early tetrapods flourished and diversified over the next 30 million years, the non- tetrapod elpistostegalians disappear from the fossil record fairly quickly in the early Frasnian around 380 million years ago, leaving the tetrapods the sole survivors of their line.
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However, it would not have possessed mammary glands, and would have fed its young, as birds do, on regurgitated food. He speculated that its language would have sounded somewhat like bird song.Naish, D. (2006). Dinosauroids Revisited Darren Naish: Tetrapod Zoology, April 23, 2011.
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Pholcus phalangioides often uses an alternating tetrapod gait (first right leg, then second left leg, then third right leg, etc.), which is commonly found in many spider species. However, frequent variations from this pattern have been documented during observations of the spiders' movements.
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Biomechanics and functional preconditions for terrestrial lifestyle in basal tetrapods, with special consideration of Tiktaalik roseae. Historical Biology 25:167-181. Clack JA. 2007. Devonian climate change, breathing, and the origin of the tetrapod stem group. Integrative and Comparative Biology. p. 1–14.
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The jugal is a skull bone found in most reptiles, amphibians, and birds. In mammals, the jugal is often called the zygomatic bone or malar bone. The prefrontal bone is a bone separating the lacrimal and frontal bones in many tetrapod skulls.
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Examples of salamanders that retain their external gills upon reaching adulthood are the olm and the mudpuppy. Still, some extinct tetrapod groups did retain true gills. A study on Archegosaurus demonstrates that it had internal gills like true fish.Florian Witzmann; Elizabeth Brainerd (2017).
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Dromaeosaurus skull. The prefrontal bone is a bone separating the lacrimal and frontal bones in many tetrapod skulls. It first evolved in the sarcopterygian clade Rhipidistia, which includes lungfish and the Tetrapodomorpha. The prefrontal is found in most modern and extinct lungfish, amphibians and reptiles.
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Herring, S. W., & Mucci, R. J. (1991). In vivo strain in cranial sutures: the zygomatic arch. Journal of morphology, 207(3), 225-239. Transitional feeding changes can be observed by examining cross sectional morphology of a suture in taxa of the fish-tetrapod transition.
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In June 2011, an amphibian identified as belonging to the species Atretochoana eiselti was photographed near Praia de Marahú, on the island of Mosqueiro. A. eiselti, previously known only from two preserved specimens dating from the late 1800s, is the largest known lungless tetrapod.
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Her name is a pun on and Tetrapod. ; : (Anime), Kana Hanazawa (CD) :A girl with glasses and green hair who is a smart, cool-headed, yet violent girl. She is a childhood friend of Tetora's. Her name is a pun on cool beauty and .
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Tetrapod Zoology. 18 January 2008. Accessed 31 January 2008 (). The scientists who described Tupandactylus did not name a Tupandactylus navigans (but instead suggested it was synonymous to Tupandactylus imperator), and Tapejara navigans was not formally reclassified as a distinct species of Tupandactylus until 2011.
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Pierce, S. E., J. A. Clack, and J. R. Hutchinson. 2012. Three-dimensional limb joint mobility in the early tetrapod Ichthyostega. Nature 486:523-U123. Amemiya, C. T., J. Alfoldi, A. P. Lee, S. H. Fan, H. Philippe, I. MacCallum, I. Braasch et al. 2013.
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Shubin, N. H., Daeschler, E. B. and Coates, M. I. 2004. The early evolution of the tetrapod humerus. – Science 304: 90–93. Due to a recent discovery of a humerus of Panderichthys that was not flattened, the specimen could be analyzed in much greater detail.
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The Permo- Carboniferous of Prince Edward Island, Canada contains trackways of tetrapods and stem-reptiles.Calder, J.H., Baird, D. & Urdang, E.B. 2004. On the discovery of tetrapod trackways from Permo-Carboniferous redbeds of Prince Edward Island and their biostratigraphic significance. Atlantic Geology, 40, 217–226.
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Tetrapod limb development involves many signaling molecules such as FGF, BMP, SHH and WNT. The apical ectodermal ridge is a structure found at the distal most tip which becomes a key signaling center for the developing limb. Surprisingly many of the same signaling pathways known to play a role in tetrapod limb development have been found to play a role in bat forelimb development but the timing, intensity, and spatial gene expression of some orthologous genes have changed. Since mice are also mammals, it is convenient to compare morphology and development of forelimbs between mice and bats; these comparisons may elucidate the genetic basis of adaptive bat wing development.
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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. Oldest tetrapod tracks from Zachelmie in relation to key Devonian tetrapodomorph body fossils Eusthenopteron Panderichthys Tiktaalik Acanthostega Ichthyostega Hynerpeton Tulerpeton Crassigyrinus Diadectes These earliest tetrapods were not terrestrial. The earliest confirmed terrestrial forms are known from the early Carboniferous deposits, some 20 million years later.
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Examples of items in the Cowan Tetrapod collection The Cowan Tetrapod Collection was founded in 1951. The collection is named after its first curator, Dr. Ian McTaggart-Cowan, and was originally named the "Cowan Vertebrate Museum". It combined several pre- existing collections, including the K. Racey birds and mammals collection, the WS Maguire and J. Wynne zoology materials, and the HR Macmillan birds collection. The collection contains over 40,000 items representing over 2,000 species of vertebrates - 18,000 mammals from 540 species, 17,500 birds and 7,000 bird eggs, and 1,600 reptiles and amphibians - making it the second largest collection of birds, mammals, reptiles and amphibians in British Columbia.
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Panderichthys in evolutionary context In January 2010, Nature reported well-preserved and "securely dated" tetrapod tracks from Polish marine tidal flat sediments approximately 397 million years old.Niedzwiedzki, G., Szrek, P., Narkiewicz, K., Narkiewicz, M and Ahlberg, P., Nature 463(7227):43–48, 2010, Tetrapod trackways from the early Middle Devonian period of Poland, 7 January 2010. These fossil tracks suggest that a group of two meter long tetrapods lived in the fully marine intertidal or lagoonal areas on the south coast of Laurussia during the time elpistostegids were living. This implies that Panderichthys is not a transitional fossil and represents its own adaptive morphology.
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Spathicephalus is an early member of the group Tetrapoda, which includes all four-limbed vertebrates. According to the most recent studies of early tetrapod phylogeny, it belongs to a clade or evolutionary grouping within Tetrapoda called Baphetoidea but lies outside a subgroup of baphetoids called Baphetidae, which form the "core" of Baphetoidea. Most recent studies of tetrapod evolutionary relationships find baphetoids to be stem group tetrapods, meaning that they branched off from other tetrapods before the most recent common ancestor of living tetrapods (amphibians, reptiles, birds, and mammals) appeared. Paleontologists recognized that Spathicephalus was a close relative of baphetids ever since D. M. S. Watson first described it in 1929.
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The question of a dermohyal in brachiopterygian fishes. Acta Zoologica, 67, 1-4. Bjerring has named the temnospondyls SelenocaraBjerring, H. C. (1997). The question of the Eotriassic tetrapod genus Wetlugasaurus in Greenland and thoughts on the fossa coniformis entopterygoidea. Meddelelser om Grønland, Geosciences 34, 1-25.
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Also designed after a namahage, Neiger Geon fights with Zui Quan attacks and his weapons are the and . He also gets a powered up form called . ;: Transforming from , Aragemaru protects the fisheries of Akita. He has tetrapod designs in his armor and is armed with the and .
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The Cistecephalus Assemblage Zone is a tetrapod assemblage zone or biozone found in the Adelaide Subgroup of the Beaufort Group, a majorly fossiliferous and geologically important geological group of the Karoo Supergroup in South Africa.Rubidge, B. S. (1995). Biostratigraphy of the Beaufort Group(Karoo Supergroup). Biostratigraphic series.
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The Daptocephalus Assemblage Zone is a tetrapod assemblage zone or biozone found in the Adelaide Subgroup of the Beaufort Group, a majorly fossiliferous and geologically important geological Group of the Karoo Supergroup in South Africa.Rubidge, B. S. (1995). Biostratigraphy of the Beaufort Group (Karoo Supergroup). Biostratigraphic series.
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Lucas, S. G., and Tanner L. H. 2007. Tetrapod biostratigraphy and biochronology of the Triassic-Jurassic transition on the southern Colorado Plateau, USA. Palaeogeography, Palaeoclimatology, Palaeoecology 244(1–4):242–256. The plant life known from this area included trees that became preserved as petrified wood.
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The deep jaw also supports this hypothesis since it would have given Acherontiscus a strong bite. Acherontiscus is the oldest known tetrapod with heterodont dentition (i.e. teeth of different shapes and sizes), predating the next oldest (the Early Permian captorhinid Opisthodontosaurus) by about 50 million years.
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Baphetes is an extinct genus of tetrapod from the Pennine Coal Measures Group and Parrot Coal, England, the Joggins Formation of Nova Scotia, and the Kladno Formation of the Czech Republic. It was first named by Richard Owen in 1854. The type species is B. planiceps.
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However, there have been some isolated specimen found in a few different localities, all from eastern European regions of Russia. Fröbisch, J. and Reisz, R. R. 2011. The postcranial anatomy of Suminia getmanovi (Synapsida: Anomodontia), the earliest known arboreal tetrapod. Zoological Journal of the Linnean Society, 162: 661–698.
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The Corona Formation has provided fossils of fish, brachiopods, a bryozoan, an insect, fossil flora including trunks and ichnofossils ascribed to Limnopus. The tracks from the Corona Formation include the oldest record of tetrapod tracks from the Southern Alps. The rugose coral Amplexus coronae was named after the formation.
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Human hand anatomy (pentadactyl) In biology, dactyly is the arrangement of digits (fingers and toes) on the hands, feet, or sometimes wings of a tetrapod animal. It comes from the Greek word δακτυλος (dáktulos) = "finger". Sometimes the ending "-dactylia" is used. The derived adjectives end with "-dactyl" or "-dactylous".
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Earlier aquatic tetrapods and tetrapod ancestors differ from temnospondyls like Phonerpeton in that their skulls were also built to withstand tension. This tension would have been experienced during suction feeding underwater. Temnospondyls like Phonerpeton were among the first tetrapods that were almost exclusively terrestrial and fed by biting.
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Some paleontologists suggest that the end-Permian tetrapod extinctions, including Aulacephalodon, may have been caused by lowered atmospheric oxygen concentrations, resulting in both environmental and organismal hypoxia. The increase in size of the internal nares and secondary palate would decrease the respiratory efficiency of large anomodont therapsids, such as Aulacephalodon. Comparison of Triassic and late- Permian therapsids shows an increase in separation between the buccal and nasal cavities and larger internal nares in Triassic therapsids, demonstrating an increased efficiency of oxygen transport in a lower-oxygen environment. An important caveat to this explanation for extinction is that hypoxia is most likely one of many compounding environmental factors that led to the end- Permian tetrapod extinction.
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Portrait of John William Dawson. Following the expedition, Charles Lyell took the fossils to be studied in Boston, where they were studied by Louis Agassiz and Jeffries Wyman at Harvard University. Agassiz first dismissed the remains as belonging to a coelacanth and Wyman believed they were those of a marine reptile related to Proteus anguinus, but after working the fossils out of the stone they'd been recovered in the scientists confirmed that the fossils represented bones from two reptiles: seven vertebrae and an ilium. At the time, only four tetrapod specimens had been recovered from coal formations around the world, meaning the eight bones recovered by Lyell and Dawson represented one-third of all Carboniferous tetrapod fossils.
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Pederpes ("Peter's Foot") is an extinct genus of early Carboniferous tetrapod, dating from 348 to 347.6 Ma in the Tournaisian age (lower Mississippian). Pederpes contains one species, P. finneyae, 1 m long. Life reconstruction of Pederpes finneyae This most basal Carboniferous tetrapod had a large, somewhat triangular head, similar to that of later American sister-genus Whatcheeria, from which it is distinguished by various skeletal features, such as a spike- like latissimus dorsi (an arm muscle) attachment on the humerus and several minor skull features. The feet had characteristics that distinguished it from the paddle-like feet of the Devonian Ichthyostegalia and resembled the feet of later, more terrestrially adapted Carboniferous forms.
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The jaw likely comes from the Altagoan Formation and, based on an analysis of fossilized pollen, dates to the late Tournaisian stage of the Early Carboniferous about 350 million years ago. The occurrence of Occidens in the Tournaisian makes it a critically important taxon because it lies within Romer's gap, a time interval spanning most of the Early Carboniferous in which almost no tetrapod fossils are known. Romer's gap separates the first appearance of tetrapods in the Late Devonian from the group's first evolutionary radiation toward the end of the Early Carboniferous. However, the relationship of Occidens to other early tetrapods both before and after the gap remain uncertain, which means that its context in tetrapod evolution remains unknown.
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Clack, J. A. (2002). A revised reconstruction of the dermal skull roof of Acanthostega gunnari, an early tetrapod from the Late Devonian. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 93(02), 163-165. These characteristics account for why osteichthyans are accepted as the sister group of tetrapods.
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Zoological Journal of the Linnean Society, 114(3), 307-348. The opening of the otic wall of the braincase can be considered a paedomorphic feature for tetrapods and is linked to the stapes functionally.Clack, J. A. (1994). Earliest known tetrapod braincase and the evolution of the stapes and fenestra ovalis.
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Bjerring , H. C. (1995). The parietal problem: how to cut this Gordian knot? Acta Zoologica, 76, 193–203. He has also analysed the basic structure of the paired limbs by comparing the pectoral and pelvic fins of the Eusthenopteron with the hindleg of the Devonian tetrapod Ichthyostega and embryonic humans.
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Johanson, Z., Ahlberg, P., & Ritchie, A. (2003). The braincase and palate of the tetrapodomorph sarcopterygian Mandageria fairfaxi: morphological variability near the fish–tetrapod transition. Palaeontology, 46(2), 271-293. This could have been driven by the need to lift the head to aid aerial respiration by using nostrils and choanae.
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Analysis of the limb bones (including the scapulocoracoid, humerus, radius, ulna, pelvis, and femur) was published in 2015, and revealed that Bunostegos walked upright on four limbs, with the body held above ground. This new information directly suggests that it could be the first tetrapod with a fully erect gait.
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It also suggests that there were greater links between the tetrapod animals across the continents in the Cretaceous. Krause et al. (2020) recovered Cifelliodon as a basal member of Allotheria, outside of the clade containing Euharamiyida and 'Multituberculata + Gondwanatheria'. Their analysis did not include Hahnodon; Vintana was recovered within Gondwanatheria.
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Tverdokhlebov, V. P., Tverdokhlebova, G. I., Surkov, M. V. and Benton, M. J. (2003). Tetrapod localities from the Triassic of the SE of European Russia. Earth-Science Reviews 60:1–66. as well as from the Bukobay Formation in the southern part of Bashkortostan in the southern Urals of European Russia.
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Caerorhachis (meaning "suitable spine" in Greek) is an extinct genus of early tetrapod from the Early Carboniferous of Scotland, probably from the Serpukhovian stage. Its placement within Tetrapoda is uncertain, but it is generally regarded as a primitive member of the group. The type species C. bairdi was named in 1977.
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Limnostygis is a dubious genus of tetrapod from the Pennsylvanian of Nova Scotia. The fragmentary holotype specimen was found in a fossilized tree stump in the Morien Group. Formerly thought to be a limnoscelid, this specimen has since been considered to be a combination of possible ophiacodont and captorhinid material.
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Markey, M. J., & Marshall, C. R. (2007). Terrestrial-style feeding in a very early aquatic tetrapod is supported by evidence from experimental analysis of suture morphology. Proceedings of the National Academy of Sciences, 104(17), 7134-7138. Comparing positionally comparable sutures in extant fish allows for the creation of a sutural morphospace.
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The Eodicynodon Assemblage Zone is a tetrapod assemblage zone or biozone which correlates to the Abrahamskraal Formation, Adelaide Subgroup of the Beaufort Group, a fossiliferous and geologically important geological Group of the Karoo Supergroup in South Africa.Rubidge, B. S. (ed.) 1995b. Biostratigraphy of the Beaufort Group (Karoo Supergroup). South African Committee of Stratigraphy.
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In coastal engineering, a tetrapod is a four- legged concrete structure used as armour unit on breakwaters. The tetrapod's shape is designed to dissipate the force of incoming waves by allowing water to flow around rather than against it, and to reduce displacement by allowing a random distribution of tetrapods to mutually interlock.
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Akmons protecting the runway at Wellington International Airport from Cook Strait. An akmon is a multi-ton concrete block used for breakwater and seawall armouring. It was originally designed in the Netherlands in the 1960s, as an improvement on the tetrapod."Development of Concrete Breakwater Armour Units" , Canadian Society for Civil Engineering, 2003.
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Whatcheeria is an extinct genus of early tetrapod from the Early Carboniferous of Iowa. Fossils have been found in 340 million year old fissure fill deposits in the town of Delta. The type species W. deltae was named in 1995. It is classified within the family Whatcheeriidae along with the closely related Pederpes.
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Acanthostega (meaning "spiny 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 fully capable of coming onto land.
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Ventastega (Venta- referring to the Venta River at the Ketleri Formation where Ventastega was discovered) is an extinct genus of stem tetrapod that lived during the Upper Fammenian of the Late Devonian, approximately 372.2 to 359 million years ago. Only one species is known that belongs in the genus, Ventastega curonica, which was described in 1996 after fossils were discovered in 1933 and mistakenly associated with a fish called Polyplocodus wenjukovi. ‘Curonica’ in the species name refers to Curonia, the Latin name for Kurzeme, a region in western Latvia. Ventastega curonica was discovered in two localities in Latvia, and was the first stem tetrapod described in Lativa along with being only the 4th Devonian tetrapodomorph known at the time of description.
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1962; 4th ed. 1970) Snakes and other legless reptiles are considered tetrapods because they are sufficiently like other reptiles that have a full complement of limbs. Similar considerations apply to caecilians and aquatic mammals. Newer taxonomy is frequently based on cladistics instead, giving a variable number of major "branches" (clades) of the tetrapod family tree.
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Chelichnus is an ichnogenus of Permian tetrapod footprint. The name means tortoise traces, because the shape of the prints was originally mistakenly thought to be produced by a tortoise. This is now known to be incorrect, as tortoises did not evolve until much later. It was first found in Corncockle Quarry in Dumfries, Scotland.
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Aytonerpeton is an extinct genus of stem-tetrapod from the Ballagan Formation of Scotland. It was one of five new genera of early limbed vertebrates from the Ballagan Formation described by Clack et al. in 2016. These vertebrates were among the only known in the world from a period of time known as Romer's gap.
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Later Devonian strata preserve primitive fishes and more evidence for early tetrapods. One important fossil site called Red Hill is found along a road cut in Clinton County. It preserves evidence of a floodplain environment that was dominated by the plant Archaeopteris. The early tetrapod Hynerpeton, an important transitional fossil, was described from Red Hill.
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33 abstract He is the discoverer of the transitional fossil tetrapod Hynerpeton bassetti, and a Devonian fish-like specimen of Sauripterus taylorii with fingerlike appendages,Daeschler, E. B. and N. H. Shubin. 1998. Fish with Fingers?. Nature 391:133. and was also part of a team of researchers that discovered the transitional fossil Tiktaalik.
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The Tropidostoma Assemblage Zone is a tetrapod assemblage zone or biozone which correlates to the lower Teekloof Formation, Adelaide Subgroup of the Beaufort Group, a fossiliferous and geologically important geological Group of the Karoo Supergroup in South Africa.Rubidge, B. S. (ed.) 1995b. Biostratigraphy of the Beaufort Group (Karoo Supergroup). South African Committee of Stratigraphy.
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The earliest known therian mammal fossil is Juramaia, from the Late Jurassic (Oxfordian stage) of China. However, molecular data suggests that therians may have originated even earlier, during the Early Jurassic. Hugall, A.F. et al. (2007) Calibration choice, rate smoothing, and the pattern of tetrapod diversification according to the long nuclear gene RAG-1.
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The Yeso Group is largely devoid of fossils. However, continued field work has gradually built up a record of marine microfossils, mostly algae and foraminiferans, trace fossils (including tetrapod footprints), and terrestrial plant fossils. In 2018, a mold of an incomplete, articulated skeleton of a eupelycosaur was discovered in lower Yeso strata.Lucas et al.
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Darren Naish is a British vertebrate palaeontologist and science writer. He obtained a geology degree at the University of Southampton and later studied vertebrate palaeontology under British palaeontologist David Martill at the University of Portsmouth, where he obtained both an M. Phil. and PhD. He is founder of the blog Tetrapod Zoology, created in 2006.
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The informal lower members contains sparse fossiliferous limestone beds containing crinoids, brachiopods, stromatolites, fusulinids, and conodonts. Outcrops near the headwaters of the Pecos River include tetrapod footprints, identified as Batrachichnus, Limnopus, Ichniotherium, Tambachichnium, Dimetropus, and Dromopus. Less identifiable specimens may be Matthewichnus, Notalacerta, and Hyloidichnus. The assemblage is consistent with a late Artinskian age.
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First Notes on the Husbandry of the Blind Cichlid Lamprologus lethops from the Congo River. Cichlid News vol. 22(1): 6-11. The waterfall climbing cavefish has several adaptions that allow it to climb and "walk" in a tetrapod-like fashion Cavefish are quite small with most species being between in standard length and about a dozen species reaching .
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Säve-Söderbergh participated in Lauge Koch's Three-year Expedition to East Greenland in 1931-1934 and 1936. He brought back fossils of Ichthyostega, by then the earliest known tetrapod, and published an extensive preliminary report on it in 1932.Säve-Söderbergh, G. (1932). Preliminary note on Devonian stegocephalians from East Greenland. Meddelelser om Gr¢nland, 94(7), 1-107.
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In terrestrial tetrapod Phonerpeton, there is compression between the frontals and parietals and a complex loading between the post parietals. There is no evidence of tensile strain in any sutures. Acanthostega fossil records demonstrate that no strain pattern was exhibited that relate to prey capture by means of suction. The load compression is similar to extant tetrapods.
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Tseajaia was described from a single, fairly complete specimen and was given its own family by Robert L. Carroll. It was originally thought to be a Seymouriamorph.Moss, J.L. (1972): The morphology and phylogenetic relationships of the Lower Permian tetrapod Tseajaia campi Vaughn (Amphibia: Seymouriamorpha). University of California Publications in Geological Sciences, vol 98, pp 1-72.
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Also at this time, seawater withdrew from the state. During the Mississippian, a primitive tetrapod left tracks in the Pottsville area. A series of swamps formed where the sea once was. The late Carboniferous Pennsylvanian flora of Pennsylvania included Annularia, Cordaites, Diplothemema, Mariopteris, Neuropteris, Odontopteris, possible Pecopteris orenulata, Pecopteris pennaeformis, Pecopteris plumosa, Sphenophyllum, and possible Sphenopteris.
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Christian Alfred Sidor is an American and paleontologist. He is currently a Professor in the Department of Biology, University of Washington in Seattle, as well as Curator of Vertebrate Paleontology and Associate Director for Research and Collections at the Burke Museum of Natural History and Culture. His research focuses on Permian and Triassic tetrapod evolution, especially on therapsids.
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The possibility that the plates may have been used to, at times, feed on bivalves has also been muted Gess, Robert W.; Whitfield, Alan K. (August 22, 2020). "Estuarine fish and tetrapod evolution: insights from a Late Devonian (Famennian) Gondwanan estuarine lake and a southern African Holocene equivalent". Biological Reviews. 95 (4): 865–888. doi:10.1111/brv.
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The Shilfsandstein Formation was deposited during the early Carnian stage of the Late Triassic (~ 228 million years ago) in a lagoonal paleoenvironment. Numerous bivalves, chondrichthyean fish such as Palaeobates, trematosaurian temnospondyls such as Metoposaurus,Benton, M. J. (1986). The Late Triassic tetrapod extinction events. In: Padian, K. (ed.): The Beginning of the Age of Dinosaurs: 303-320; Cambridge.
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Amphibians are ectothermic, tetrapod vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Thus amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this.
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The researchers of the paper commented that "It is difficult to say whether this character distribution implies that Tiktaalik is autapomorphic, that Panderichthys and tetrapods are convergent, or that Panderichthys is closer to tetrapods than Tiktaalik. At any rate, it demonstrates that the fish–tetrapod transition was accompanied by significant character incongruence in functionally important structures."p. 638.
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A trace fossil known as Hermundurichnus fornicatus of a tetrapod resting on a lake bed may have been attributed to Diplocaulus or an animal like it. This trace indicates that the underside of nectrideans was covered in small, diamond-shaped scales and that the "horns" of the skull were connected with the body by flaps of skin.
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This bears a small pseudobranch that resembles a gill in structure, but only receives blood already oxygenated by the true gills. The spiracle is thought to be homologous to the ear opening in higher vertebrates.Laurin M. (1998): The importance of global parsimony and historical bias in understanding tetrapod evolution. Part I-systematics, middle ear evolution, and jaw suspension.
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Furthermore, many of these same principles may be applied to climbing without trees, such as on rock piles or mountains. The earliest known tetrapod with specializations that adapted it for climbing trees was Suminia, a synapsid of the Late Permian, about 260 million years ago. Some animals are exclusively arboreal in habitat, such as the tree snail.
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Because these features are lost early in tetrapod evolution, this may be evidence that aïstopods diverged from other tetrapods soon after the origin of digits. The ribs were slender, either single or double-headed, with the head shaped like a letter "K". There is no trace of limbs or even limb girdles in any known fossil, and the tail was short and primitive.
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The early tetrapod Acanthostega had at least three and probably four pairs of gill bars, each containing deep grooves in the place where one would expect to find the afferent branchial artery. This strongly suggests that functional gills were present. Some aquatic temnospondyls retained internal gills at least into the early Jurassic. Evidence of clear fish-like internal gills is present in Archegosaurus.
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Lungfish appeared approximately 400 million years ago. It is a species that endured rapid evolution during the Devonian era, which became known as the dipnoan renaissance. The Acanthostega species, known as the fish with legs, is considered a tetrapod by structural findings but is postulated to have perhaps never left the aquatic environment. Its legs are not well-suited to support its weight.
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The first neck vertebra that evolved permitted the animals to have flexion and extension of the head so that they can see up and down. The second neck vertebra evolved to allow rotation of the neck for moving the head left and right. As tetrapod species continued to evolve on land, adaptations included seven or more vertebrae, allowing increasing neck mobility.
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Concavenator: an incredible allosauroid with a weird sail (or hump)... and proto-feathers?. Tetrapod Zoology, September 9, 2010. This interpretation was supported by Christian Foth and others in 2014. The hypothesis that the bumps along the ulna represented muscular insertion points or ridges was subsequently examined, and the results presented, at the 2015 meeting of the Society of Vertebrate Paleontology.
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The total body is estimated to have measured about 1.5 m (5 ft) in length. Upon its description, Elginerpeton was allied with Obruchevichthys in the family Elginerpetontidae. A biomechanical analysis of stegocephalian jaws has indicated that Elginerpeton had an unusual feeding habit among tetrapod relatives. Its jaws were thin, and plotted as the most susceptible to high stresses among the sample group.
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Obruchevichthys is an extinct genus of tetrapod from Latvia during the Late Devonian. When the jawbone, the only known fossil of this creature, was uncovered in Latvia, it was mistaken as a lobe-fin fish. However, when it was analyzed, it proved to hold many similarities to Elginerpeton, from Scotland. It was then declared belonging to the earliest group of tetrapods.
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Nine genera of Devonian tetrapods have been described, several known mainly or entirely from lower jaw material. All but one were from the Laurasian supercontinent, which comprised Europe, North America and Greenland. The only exception is a single Gondwanan genus, Metaxygnathus, which has been found in Australia. The first Devonian tetrapod identified from Asia was recognized from a fossil jawbone reported in 2002.
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Pholidogaster ('scaly stomach') is an extinct genus of tetrapod that lived during the Middle Carboniferous period (late Viséan to early Serpukhovian). Pholidogaster is known from only two specimens found in Gilmerton, Scotland. Historically it was one of the first to show science the evolutionary link between fish and amphibians. This animal had a very long and slender body, with small and feeble limbs.
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By the time the Emsian epoch starts, only a few genera, such as Duyunolepis and Wumengshanaspis, survive, with most others already extinct. The last galeaspid is an as yet undescribed species and genus from the Fammenian epoch of the Late Devonian, found in association with the tetrapod Sinostega and the antiarch placoderm Remigolepis, in strata from the Northern Chinese province of Ningxia.
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Figure 3. Four different structures of nanoparticles, which have at least 1 dimension in the 1–100 nm range, retaining quantum confinement. Left is a nanocrystal, next to it is nanorod, third is tetrapod, and right is hyperbranched. For polymers used in this device, hole mobilities are greater than electron mobilities, so the polymer phase is used to transport holes.
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Land- mammal ages mostly represent intervals in the Cenozoic; they have not been proposed for the Mesozoic. However, related systems have been proposed for other periods of prehistory. Land-vertebrate "ages" (LVAs) based primarily on dinosaur faunas have been proposed for the late Cretaceous in western North America. The most widely utilized pre-Cenozoic tetrapod biochronology system involves Land vertebrate faunachrons (LVFs).
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Furthermore, they reported an increase in crocodylomorph disparity across the Triassic-Jurassic boundary, which suggests there was rapid radiation of adaptation among crocodylomorphs. They hypothesize this was a result of the extinction's "decimation" of pseudosuchian and tetrapod lineages. The study concludes that the extinction was important for the evolutionary success of Goniopholididae. A phylogenetic analysis by Brandelise de Andrade et al.
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Densignathus is an extinct genus of early stem-tetrapod from the Late Devonian of Pennsylvania in the United States. A lower jaw has been found from the Red Hill fossil site, which is known for a diversity of lobe-finned fishes and other early tetrapods like Hynerpeton. The type species, Densignathus rowei, was named by paleontologist Douglas Rowe in 2000.
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In their natural habitat, eggs hatch with the first rains in November, the growth is rapid, and adulthood is reached by January, at which time they breed. By late February or early March, females have deposited the eggs which will hatch the next year, and the entire population dies until the next hatching. No other tetrapod has exhibited such a short lifespan.
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Diagrams of skulls from S. baylorensis and S. sanjuanensis. The skull was composed of many smaller plate-like bones. The configuration of skull bones present in Seymouria was very similar to that of far more ancient tetrapods and tetrapod relatives. For example, it retains an intertemporal bone, which is the plesiomorphic ("primitive") condition present in animals like Ventastega and embolomeres.
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A smaller opening, the spiracle, lies in the back of the first gill slit. This bears a small pseudobranch that resembles a gill in structure, but only receives blood already oxygenated by the true gills. The spiracle is thought to be homologous to the ear opening in higher vertebrates.Laurin M. (1998): The importance of global parsimony and historical bias in understanding tetrapod evolution.
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The expression of MRAP was found to be regulated by ACTH as well as lipopolysaccharides and, in rats, is affected by diurnal variation. Phylogenetic studies revealed the existence of MRAP orthologs in different piscine species such as zebrafish and tetrapod and has also been detected in mammals and chicken. MRAP is thought to be originated as a result of R2 genome duplication event.
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The fitting of these two portions created the most complete skull of a burnetiid therapsid to date Day Michael O., Ramezani Jahandar, Bowring Samuel A., Sadler Peter M., Erwin Douglas H., Abdala Fernando and Rubidge Bruce S. When and how did the terrestrial mid-Permian mass extinction occur? Evidence from the tetrapod record of the Karoo Basin, South Africa282Proc. R. Soc. B .
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In 1967, the first tetrapod remains in Antarctica were discovered by New Zealander Peter Barrett, his finding eventually lending support to the theory of continental drift. Two years later, in 1969, an NZARP party of six women became the first women to reach the South Pole. Some more of NZARP's discoveries include, Ball Glacier, Atkinson Glacier, Findlay Range, Thomas Heights, and Mount Bradshaw.
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Oligokyphus were small tetrapod, terrestrial animals. They have long been considered as mammaliomorphs, a link between earlier synapsids and modern mammals. It is believed these animals were primarily land dwelling, living amongst small shrubs or bushes. It is also thought that Oligokyphus fed on seeds or nuts, as their teeth resemble those of modern animals that also feed on seeds and nuts.
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A smaller opening, the spiracle, lies in the back of the first gill slit. This bears a small pseudobranch that resembles a gill in structure, but only receives blood already oxygenated by the true gills. The spiracle is thought to be homologous to the ear opening in higher vertebrates.Laurin M. (1998): The importance of global parsimony and historical bias in understanding tetrapod evolution.
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Barton, R. A., Purvis, A., & Harvey, P. H. (1995). Evolutionary radiation of visual and olfactory brain systems in primates, bats and insectivores. Philosophical Transactions of the Royal Society of London B: Biological Sciences, 348(1326), 381-392. Evolutionary loss of the accessory olfactory system is observed in multiple tetrapod lineages, which is believed to be caused by the overlapping redundancy of function with the main olfactory system.
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The skull of Brasilitherium provides useful information when discerning the emergence of a true nose in mammals. Brasilitherium was not a mammal but indeed a synapsida tetrapod that served as a close predecessor to the first mammaliaforms. The emergence of turbinates can be recognized through the observation of this 227 million year old protomammal.Ruf, I., Maier, W., Rodrigues, P. G., & Schultz, C. L. (2014).
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These localities, located between the Ndatira and Njalila rivers, belong to the fluviolacustrine mudstone-sandstone sequence in the middle of the Lifua Member of the Manda beds of Ruhuhu Basin in Tanzania. Based on comparison with the better studied tetrapod fauna of Subzone C of the Cynognathus Assemblage Zone of South Africa, this member is considered to date to the Anisian stage of the early Middle Triassic.
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He died at Solbacken, a sanatorium in Dalarna. His research on the Devonian tetrapod Ichthyostega was continued by Erik Jarvik. Säve-Söderbergh was made an honorary doctor at Uppsala in 1942 and was elected member of the Royal Swedish Academy of Sciences shortly before his death. He was the brother of egyptologist Torgny Säve-Söderbergh (1914–1998) and father of Bengt Säve-Söderbergh (b.
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P. N. Kolosov, G. V. Ivensen, T. E. Mikhailova, S. M. Kurzanov, M. B. Efimov and Y. M. Gubin. 2009. Taphonomy of the Upper Mesozoic Tetrapod Teete Locality (Yakutia). Paleontological Journal 43(2):201-207 Khurendukhosaurus was a small choristodere, approximately long at most. Efimov and Storrs regarded it as a basal member of Choristodera, but Skutschas was unable to confirm this in a phylogenetic analysis.
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The paired fins of the early sarcopterygians were smaller than tetrapod limbs, but the skeletal structure was very similar in that the early sarcopterygians 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.
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The first is agonistic behaviour within a species. In most vertebrates, including dinosaurs, this behaviour is accompanied by structures for display or combat. Some researchers believe this phenomenon would have been implausible considering there is no modern tetrapod analogue that uses the tail for this purpose. These paleontologists instead propose that ankylosaurids made use of their broad, flat skull for head-butting between individuals.
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The genome of Latimeria chalumnae was sequenced in 2013 to provide insight into tetrapod evolution. The coelacanth was long believed to be the closest relative to the first tetrapods on land due to its body characteristics. However, genetic sequencing proved that the lungfish is in fact the closest relative to land tetrapods. The full sequence and annotation of the entry is available on the Ensembl genome browser.
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Energosuchus (meaning "active crocodile" in Greek) is an extinct genus of rauisuchian. Fossils are present from the upper Karyomayol and lower Synya Formations outcropping along the banks of the Bolshaya Synya River in the Timan-North Urals region in northern European Russia,Novikov, I. V. (1994). Continental Triassic biostratigraphy of the Timan–North Urals region using tetrapod fauna. Trudy Paleontologicheskogo Instituta 261:1–139.
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It is postulated that this is how pharyngeal slits first assisted in filter-feeding, and later with the addition of gills along their walls, aided in respiration of aquatic chordates. These repeated segments are controlled by similar developmental mechanisms. Some hemichordate species can have as many as 200 gill slits. Pharyngeal clefts resembling gill slits are transiently present during the embryonic stages of tetrapod development.
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Type C cycles begin with bioturbated mudstone which abruptly transitions into a thick sequence of limestone. The limestone can be characterized as thin layers of fossil-rich grainstone interbedding with broader layers of packstone. Rarely, brown laminated mudstone may be present above the limestone. The upper part of the cycle involves conglomerate covered by sandstone and siltstone filled with plant fragments, ripple marks, and occasionally tetrapod footprints.
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The name, originally coined around the genus Elpistostege, later become a synonym for Panderichthyida. In most analyses, the group as traditionally imagined is actually an evolutionary grade, the last "fishes" of the tetrapod stem line, though Chang and Yu (1997) treated them as the sister clade to Tetrapoda. Elpistostegalia was re-defined as a clade containing Panderichthys and tetrapods. Below is a cladogram from Swartz, 2012.
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Pretectal influences mediated by NPY are phylogenetically conserved properties in tetrapod vertebrates. (Combined after Ewert 1974 and 2004) Jörg-Peter Ewert pioneered the study of feature detection in toad vision. He made significant progress by taking advantage of the common toad's natural prey catching behavior. To study toad behavior, he placed the toad in a cylindrical glass container at a fixed distance from the stimulus.
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Dolomitization of carbonate rocks of Irati Formation (Permian) from São Paulo State In 1999, Carvalho and Bertini named a fossil of tetrapod reptiles identified in the city of Marília "Mariliasuchus amarali" in his honor. Amaral was also a member of the Brazilian Academy of Sciences. Deceased member - Brazilian Academy of Sciences Amaral was a nephew of the Brazilian painter and designer Tarsila do Amaral.
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On the origin of the tetrapod limb. Acta Zoologica 14, 185–295. (2) Antecedents were present in the fins of early sarcopterygian fish. However, 2008 research which created a three-dimensional reconstruction of a Panderichthys, a coastal fish from the Devonian period 385 million years ago, shows that these animals already had many of the homologous bones present in the forelimbs of limbed vertebrates.
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The type species of Whatcheeria, W. deltae, was named in 1995. Whatcheeria is named after What Cheer, Iowa, the hometown of the man who discovered the first skeletons of the animal. The species is named after Delta, Iowa, the location where the fossils were uncovered. Hundreds of tetrapod fossils were found in the locality, and the majority of these specimens are thought to belong to Whatcheeria.
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Late Devonian fish and tetrapods Panderichthys was alive during the late Devonian (Frasnian) in Lode, Latvia. Lode is known to be a marginal marine environment and it has been hypothesized that Panderichthys was adapted for movement in shallow and debris filled waters.Clack, Jennifer A. "Devonian climate change, breathing, and the origin of the tetrapod stem group." Integrative and Comparative Biology 47.4 (2007): 510-523.
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Romer's gap is an example of an apparent gap in the tetrapod fossil record used in the study of evolutionary biology. Such gaps represent periods from which excavators have not yet found relevant fossils. Romer's gap is named after paleontologist Alfred Romer, who first recognised it.By 1955 (perhaps even earlier), Romer states that few good fossils of tetrapods have been recovered from early Carboniferous deposits.
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There are several cases of reported trackways of the earliest land-going vertebrates, also known as tetrapods. These trackways provide crucial insights to the study of the transition of aquatic to terrestrial lifestyles in vertebrate evolution. Such fossils help to illuminate not only the timing of this keystone transition of evolutionary history but also what the earliest forms of tetrapod locomotion may have entailed.
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Among terrestrial vertebrates, the main victims were dinocephalian therapsids, which were one of the most common elements of tetrapod fauna of the Guadalupian; only one dinocephalian genus survived the Capitanian extinction event. The diversity of the anomodonts that lived during the late Guadalupian was cut in half by the Capitanian mass extinction. Terrestrial survivors of the Capitanian extinction event were generally to and commonly found in burrows.
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The sternum was also lacking in this animal, and the forelimbs were more paddled-shaped, possibly indicating a greater importance of the forelimbs in movement. The pectoral girdle was formed by the paired clavicles, interclavical, scapulae, and coracoids. Keichousaurus was a primitive quadrupedal tetrapod with limbs laterally placed to the body. Different parts of Keichousaurus grew at different rates, a phenomenon called allometric growth.
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Boreogomphodon jeffersoni was named in 1990. Its teeth and cranial bones are the most common tetrapod fossils in the Turkey Branch Formation. Boreogomphodon was distinguished from other traversodontids like the African Luangwa and the South American Traversodon on the basis of its postcanine teeth. Most traversodontids have lower postcanine teeth with two cusps, but Boreogomphodon was the first traversodontid found with three cusps on its lower postcanine teeth.
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Much of the genetic machinery that builds a walking limb in a tetrapod is already present in the swimming fin of a fish.Shubin, Neil (2009) Your inner fish: A journey into the 3.5 billion year history of the human body Vintage Books. . UCTV interviewClack, Jennifer A (2012) "From fins to feet" Chapter 6, pages 187–260, in: Gaining Ground, Second Edition: The Origin and Evolution of Tetrapods, Indiana University Press. .
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They could not have reached what is now China until the Middle Permian because, prior to that time, the Tethys Sea separated it from the rest of Laurasia. The group does not seem to have diversified to the same extent in the east as they did in the west given that no diadectids are known from Russia, which has an extensive fossil record of Early and Middle Permian tetrapod assemblages.
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Gould,Stephen Jay (1993) "Bent Out of Shape" in Eight Little Piggies: Reflections in Natural History. Norton, 179–94. . Fins or flippers of varying forms and at varying locations (limbs, body, tail) have also evolved in a number of other tetrapod groups, including diving birds such as penguins (modified from wings), sea turtles (forelimbs modified into flippers), mosasaurs (limbs modified into flippers), and sea snakes (vertically expanded, flattened tail fin).
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Paralititan represents the first tetrapod reported from the Bahariya Formation since Romer's publication of 1935.alt=The holotype specimen of Paralititan, CGM 81119, was found in a layer of the Bahariya Formation, dating from the Cenomanian. It consists of a partial skeleton lacking the skull. It is incomplete, apart from bone fragments containing two fused posterior sacral vertebrae, two anterior caudal vertebrae, both incomplete scapulae, two humeri and a metacarpal.
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In Acanthostega, a basal tetrapod, the gill-covering bones have disappeared, although the underlying gill arches are still present. Besides the opercular series, Acanthostega also lost the throat-covering bones (gular series). The opercular series and gular series combined are sometimes known as the operculo-gular or operculogular series. Other bones in the neck region lost in Acanthostega (and later tetrapods) include the extrascapular series and the supracleithral series.
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They are segmented and appear as a series of disks stacked one on top of another. They may have been derived from dermal scales. The genetic basis for the formation of the fin rays is thought to be genes coded for the production of certain proteins. It has been suggested that the evolution of the tetrapod limb from lobe-finned fishes is related to the loss of these proteins.
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Leonid Petrovich Tatarinov (; November 12, 1926 — August 24, 2011) was a Russian and Soviet paleontologist and evolutionary biologist. He was an Academician of the USSR Academy of Sciences (1981) and Russian Academy of Sciences (1991), director of the Paleontological Institute (1975 - 1992) and editor-in-chief of Paleontological journal () (1976 - 2001). His research interests were in the comparative anatomy of vertebrates, tetrapod phylogeny, and evolution.A.Yu. Rozanov et al.
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Hynerpeton also has several autapomorphies, unique features which no other known stem-tetrapod possesses. The inner face of the scapulocoracoid has a large, deep depression known as a subscapular fossa. The upper rim of this depression is very roughly textured due to being covered with muscle scars. The rear edge of the subscapular fossa, on the other hand, is formed by a massive raised area, known as an infraglenoid buttress.
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Ymeria is an extinct genus of early stem tetrapod from the Devonian of Greenland. Of the two other genera of stem tetrapods from Greenland, Acanthostega and Ichthyostega, Ymeria is most closely related to Ichthyostega, though the single known specimen is smaller, the skull about 10 cm in length. A single interclavicle resembles that of Ichthyostega, an indication Ymeria may have resembled this genus in the post-cranial skeleton.
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The holotype skull was figured in 1988 by R. E. Fordyce and Australodelphis mirus first appeared as a nomen nudum in E. H. Colbert's 1991 "Mesozoic and Cainozoic tetrapod fossils from Antarctica". A second species of Australodelphis was noted by R. E. Fordyce and P. G. Quilty in their 1993 publication on the stratigraphic context of the Marine Plain sediments, but this second species has yet to be formally described.
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Entradasuchus (meaning "Entrada [Sandstone and Ranch] crocodile") is a genus of crocodyliform, an early member of the group including crocodilians. The only known specimen was found in rocks of the Middle Jurassic Entrada Sandstone of Entrada Ranch, Grand County, Utah. Middle Jurassic terrestrial tetrapods are very rare, and Entradasuchus was the first unequivocal North American Middle Jurassic nonmarine tetrapod known from body fossils when it was described (1995).
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The first tetrapod or land-living vertebrate from Antarctica was found in the Fremouw Formation and described in 1968. It was represented by a small bone fragment that is probably part of the left mandible of a temnospondyl amphibian. The bone was found the previous year by a researcher from Ohio State University who was studying the geology of the Transantarctic Mountains. The animal was later named Austrobrachyops jenseni.
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This site is a highway roadcut located across the state line from Glen Lyn, Virginia. It preserves a tidal deltaic sequence near the middle of the Bluefield Formation. Tetrapod trackways from this site have been given the species name Hylopus hamesi, and were likely made by Proterogyrinus or a closely related animal. The site has also produced a single complete skeleton of a basal actinopterygiian fish, the holotype of Bluefieldius mercerensis.
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Odontocyclops specimens have been found both in the Karoo Basin of South Africa and the Madumabisa Mudstone of the Luangwa Valley of Zambia. The Karoo Basin was originally formed in the Late Carboniferous resulting from the collision of the paleo-Pacific plate with the Gondwanan plate.Smith, R. M. H. 1995. Changing fluvial environments across the Permian-Triassic boundary in the Karoo basin, S. Africa and possible causes of tetrapod extinctions.
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The museum houses a collection of more than two million specimens, some dating back to as early as the 1910s. These specimens are divided into six main subcollections - the Cowan Tetrapod Collection, the Marine Invertebrate Collection, the Herbarium, the Spencer Entomological Collection, the Fish Collection, and the Fossil Collection - and over 500 permanent exhibits. Most items are accompanied by a description card briefly outlining details like the species and provenance information.
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After the 9.0 earthquake and subsequent tsunami that hit Japan on March 11, 2011, and the destruction of the Fukushima Daiichi Nuclear Power Plant, the industry went on a quest of providing robots able to do dangerous work at the power plant. One such solution was the HAL exoskeleton. However, the HAL exoskeleton required a human pilot. On November 23, 2012, Toshiba presented a Tetrapod which failed during the presentation.
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Its absence in fish and aquatic arthropods is notable, as many have life stations similar to a terrestrial or tetrapod counterpart, or could otherwise make use of the added flexibility. The word "neck" is sometimes used as a convenience to refer to the region behind the head in some snails, gastropod mollusks, even though there is no clear distinction between this area, the head area, and the rest of the body.
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TetZooCon is an annual meeting themed around the contents of the Tetrapod Zoology blog. The convention was first held on 12 June 2014 and has taken places in various venues in London. The convention involves talks on a variety of subjects, ranging from palaeontology to cryptozoology, as well as workshops. The convention is organised by Naish and Conway; Darren traditionally gives a talk himself, whereas John Conway hosts a workshop.
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Mammal trackways are among the least common trackways. Mammals were not often in mud, or riverine environments; they were more often in forestlands or grasslands. Thus the earlier tetrapods or proto-tetrapods would yield the most fossil trackways. The Walchia forest of Brule, Nova Scotia has an example of an in situ Walchia forest, and tetrapod trackways that extended over some period of time through the forest area.
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Ancestry also plays a role in limiting or enabling cranial kinesis. Significant cranial kinesis is rare in mammals (the human skull shows no cranial kinesis at all). Birds have varying degrees of cranial kinesis, with parrots exhibiting the greatest degree. Among reptiles, crocodilians and turtles lack cranial kinesis, while lizards possess some, often minor, degree of kinesis and snakes possessing the most exceptional cranial kinesis of any tetrapod.
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The Otis Chalk localities that are situated in the Colorado City Formation form the basis of the Otischalkian Land Vertebrate Faunachron (LVF), which is defined by the first appearance of Parasuchus.Lucas, S. G., Hunt, A. P., Heckert, A. B., and Spielmann, J. A., (2007) Global Triassic tetrapod biostratigraphy and biochronology: 2007 status: New Mexico Museum of Natural History and Science Bulletin, v. 41 (The Global Triassic), p. 229- 240.
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House sparrow, Passer domesticus The following outline is provided as an overview of and topical guide to birds: Birds (class Aves) – winged, bipedal, endothermic (warm-blooded), egg-laying, vertebrate animals. There are around 10,000 living species, making them the most varied of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic, to the Antarctic. Extant birds range in size from the bee hummingbird to the ostrich.
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Much more commonly, it contains trace fossils, especially the tetrapod footprints of Chirotherium. The type locality for these animal tracks is Hildburghausen in the Thuringian part of Franconia, where it occurs in the so-called Thuringian Chirotherium Sandstone (Thüringer Chirotheriensandstein, main Middle Bunter Sandstone).Hartmut Haubold: Die Saurierfährten Chirotherium barthii Kaup, 1835 \- das Typusmaterial aus dem Buntsandstein bei Hildburghausen/Thüringen und das "Chirotherium-Monument". Publication by the Natural History Museum, Schleusingen, vol.
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In their 2012 monograph on vertebrates of the Redonda Formation, however, Justin Spielmann and Spencer Lucas decided that the material reported by Heckert et al. was sufficiently distinct to be recognized as a distinct genus and species, which they named Apachesuchus heckerti in honor of Andrew Heckert.J. A. Spielmann and S. G. Lucas. 2012. Tetrapod fauna of the Upper Triassic Redonda formation, East-Central New Mexico: the characteristic assemblage of the Apachean land-vertebrate faunachron.
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Westlothiana ("animal from West Lothian") is a genus of reptile-like tetrapod that lived about 338 million years ago during the latest part of the Visean age of the Carboniferous. Members of the genus bore a superficial resemblance to modern-day lizards. The genus is known from a single species, Westlothiana lizziae. The type specimen was discovered in the East Kirkton Limestone at the East Kirkton Quarry, West Lothian, Scotland in 1984.
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The diapsids (a subgroup of the sauropsids) began to diversify during the Triassic, giving rise to the turtles, crocodiles, and dinosaurs. In the Jurassic, lizards developed from other diapsids. In the Cretaceous, snakes developed from lizards and modern birds branched from a group of theropod dinosaurs. By the late Mesozoic, the groups of large, primitive tetrapod that first appeared during the Paleozoic such as temnospondyls and amniote-like tetrapods had gone extinct.
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The Museum is located near the Place Garibaldi. It was designed by two architects, Yves Bayard and Henri Vidal, and is shaped as a tetrapod arch straddling the course of the Paillon. The monumentality of the project developed to cross the Paillon allows connection through a terrace, called the Promenade des Arts, from the Museum to the Theater. With its square plan, the architecture of the building is inspired by neo-classicism rules.
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Over 20 genera of aetosaurs have been described, and recently there has been controversy regarding the description of some of these genera. Aetosaur fossil remains are known from Europe, North and South America, parts of Africa and India. Since their armoured plates are often preserved and are abundant in certain localities, aetosaurs serve as important Late Triassic tetrapod index fossils. Many aetosaurs had wide geographic ranges, but their stratigraphic ranges were relatively short.
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The maxillary tooth row was in its entirety transversely rotated, its normal rear 90° everted towards the front. This was matched by an identical rotation of the dentary of the lower jaw. As a result, no other tetrapod had all of its teeth located as far to the front as Nigersaurus. Teeth at different growth stages, Museo di Storia Naturale di Venezia The slender teeth had slightly curved crowns, which were oval in cross-section.
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Tseajaia is an extinct genus of tetrapod. It was a basal diadectomorph that lived in the Permian of North America.Time Traveler: In Search of Dinosaurs and Other Fossils from Montana to Mongolia by Michael Novacek The skeleton is that of a medium-sized, rather advanced reptile-like amphibian. In life it was about long and may have looked vaguely like an iguana, though slower and with a more amphibian foot without claws.
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The full complement of bones of the tetrapod skull roof, as seen in the labyrinthodont Xenotosuchus The skull roof, or the roofing bones of the skull, are a set of bones covering the brain, eyes and nostrils in bony fishes and all land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium. In comparative anatomy the term is used on the full dermatocranium.Romer, A.S. & T.S. Parsons. 1977.
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In 1952, Swedish paleontologist Erik Jarvik first described the first species, Eusthenodon wangsjoi of the genus Eusthenodon. The specimen was retrieved in 1936 from the richly fossiliferous sediments of the Upper Devonian sequences of East Greenland, a region that gained tremendous attraction by vertebrate paleontologists after the discovery of Ichthyostega, the earliest known tetrapod. The given name of the genus, Eusthenodon, refers to the distinctly large tusks present in the upper and lower jaws.
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Most synapsids possess only 3 sacral vertebrae, which articulate with the ilium and are vital in tetrapod locomotion. According to Griffin et. al., “The ancestral synapsid probably possessed two sacral vertebrae (Romer 1956; LeBlanc and Reisz 2014), with Therapsida and some non-therapsid lineages (e.g., Caseidae, Edaphosauridae, Sphenacodontidae) incorporating a third sacral from the caudal series.” Synapsids display very little variation in the number of presacral vertebrae, as their axial column is highly conserved.
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Tall lycopods and horsetails dominated the wetlands of Gondwana in the Early Permian. Insects co-evolved with glossopterids across Gondwana and diversified with more than 200 species in 21 orders by the Late Permian, many known from South Africa and Australia. Beetles and cockroaches remained minor elements in this fauna. Tetrapod fossils from the Early Permian have only been found in Laurasia but they became common in Gondwana later during the Permian.
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Cochleosaurus ('spoon lizard') is a name of a tetrapod belonging to Temnospondyli, which lived during the late Carboniferous period (Moscovian, about 310 million years ago). The great abundance of its remains (about 50 specimens) have been found in the Kladno Formation of the Czech Republic, near Nýřany in Central Europe and in the Morien Group of Nova Scotia in North America.Cochleosaurus at Fossilworks.org It was a creature of medium size, measuring 120-160 centimeters.
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The earliest known tetrapod with specializations that adapted it for climbing trees was Suminia, a synapsid of the late Permian, about 260 million years ago. Some invertebrate animals are exclusively arboreal in habitat, for example, the tree snail. Brachiation (from brachium, Latin for "arm") is a form of arboreal locomotion in which primates swing from tree limb to tree limb using only their arms. During brachiation, the body is alternately supported under each forelimb.
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Tetrapods were initially understood to have first developed five digits as an ancestral characteristic, which were then reduced or specialized into a number of uses. Certain animals retained 'primitive' forelimbs, such as pentadactylous (five-fingered) reptiles and primates. This has mostly held true, but the earliest tetrapod or "fishapod" ancestors may have had more than five digits. This was notably challenged by Stephen Jay Gould in his 1991 essay "Eight (Or Fewer) Little Piggies".
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A. eiselti is the largest tetrapod to lack lungs, double the size of the next largest. Caecilians such as Atretochoana are limbless amphibians with snake-like bodies, marked with rings like those of earthworms. It has significant morphological differences from other caecilians, even the genera most closely related to it, even though those genera are aquatic. The skull is very different from those of other caecilians, giving the animal a broad, flat head.
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Amniotes include synapsids (mammals along with their extinct kin) and sauropsids (reptiles and birds), as well as their ancestors, back to amphibians. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes. In eutherian mammals (such as humans), these membranes include the amniotic sac that surrounds the fetus. These embryonic membranes and the lack of a larval stage distinguish amniotes from tetrapod amphibians.
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The long neck distinguishing feature of the giraffe. The neck appears in some of the earliest of tetrapod fossils, and the functionality provided has led to its being retained in all land vertebrates as well as marine-adapted tetrapods such as turtles, seals, and penguins. Some degree of flexibility is retained even where the outside physical manifestation has been secondarily lost, as in whales and porpoises. A morphologically functioning neck also appears among insects.
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None of the impressions are reported to include evidence of body dragging, though one includes evidence of tail drag. This is interpreted to illustrate that the movement shown here demonstrates the animal fully suspending its body with its limbs. Additionally, one of the tracks is interpreted to preserve digitation of the limbs, which are reported to possess 5 digits. These trackways then imply that by the Late Devonian a "typical" tetrapod condition had fully evolved.
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Labidosaurikos specimens have been found in Permian red beds of North American. Specimens have been found within Hennessey shale in Crescent, Oklahoma as well as the Lower Vale, Choza, and Arroyo Formations in northern central Texas. These locations have yielded critical information about early tetrapod evolution and Captorhinids are extremely common in these deposits. All locations have been correlated with each other to be formed in the Lower Permian sometime within the Kungurian.
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Proterosuchus fossils are found in the Lystrosaurus Assemblage Zone of the Beaufort Group in South Africa. Proterosuchus was the first new species to arrive in the Karoo environment after the Permian–Triassic extinction. Proterosuchus and the therocephalian Moschorhinus were the largest carnivores in the ecosystem at the time, and soon after the extinction Moschorhinus declined and went extinct while Proterosuchus thrived. The most common tetrapod in Proterosuchus's environment was the herbivorous dicynodont Lystrosaurus.
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Some analyses published since 2007 have argued that adelospondyls such as Acherontiscus may not actually be lepospondyls, instead being close relatives or members of the family Colosteidae. This would indicate that they evolved prior to the split between the tetrapod lineage that leads to reptiles (Reptiliomorpha) and the one that leads to modern amphibians (Batrachomorpha). Members of this genus were probably aquatic animals that were able to swim using snake-like movements.
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Phylogenetic studies performed since Ruta & Coates (2007) have generally supported this hypothesis. The following cladogram is the strict consensus tree of 9 MPTs found in the reweighted analysis of Ruta & Coates (2007). The reweighted analysis is similar to a typical phylogenetic analysis, but certain transitions involve different numbers of steps due to different evolutionary traits being weighted. The weighting of traits relates to how consistent the traits appear among the tetrapod family tree.
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Tripod gaits are most commonly used at high speeds, though it can be used at lower speeds. The tripod gait is less stable than wave-like and tetrapod gaits, but it is theorized to be the most robust. This means that it is easier for an insect to recover from an offset in step timing when walking in a tripod gait. The ability to respond robustly is important for insects when traversing uneven terrain.
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The type specimen was originally described as Macromerium scoticum and lacked a complete skull. With subsequent discoveries, Crassigyrinus is now known from three skulls, one of which is in articulation with a fairly complete skeleton, and two incomplete lower jaws. Crassigyrinus grew up to 2 meters in length, coupled with tiny limbs and unusually large jaws. Crassigyrinus is taxonomically enigmatic, having confused paleontologists for decades with its apparent fish-like and tetrapod features.
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DOI: 10.1080/02724634.2015.1008698. In addition, Sidor et al. (2010)Sidor, C. A., K. D. Angielczyk, D. M. Weide, R. M. H. Smith, S. J. Nesbitt, and L. A. Tsuji. 2010. Tetrapod fauna of the lowermost Usili Kruger et al.—A new burnetiamorph from Malawi (e1008698-9) Downloaded by [The Library, University of Witwatersrand] at 23:15 01 November 2015 Formation (Songea Group, Ruhuhu Basin) of southern Tanzania, with a new burnetiid record.
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To celebrate ten years as a UNESCO heritage site, the Joggins Fossil Institute hosted the first Joggins Research Symposium on 22 September 2018. A number of improvements were suggested to improve the site for research and educational purposes, including the construction of a storage facility for fossil trees recovered from the cliffs which could bear tetrapod fossils, the development of machine learning software to better identify fossils at the site, and revision of the Special Places Protection Act.
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Dozens of tetrapod, invertebrate, and plant fossils have been recovered from the Joggins Formation. A diverse array of ichnofossils have also been found at Joggins, including vertebrate trackways, invertebrate trace fossils, tunnel structures, rhizoliths, and possibly wood borings. Fish coprolites are abundant in the limestone of the Joggins Formation, averaging lengths of 2-3 cm (0.79-1.18 in). Research into these coprolites suggests that carnivorous fishes were far more prevalent in the region than herbivorous ones.
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Gealy Spur () is a high rock spur on the west side of Beardmore Glacier, Antarctica. The spur descends northeast from Mount Marshall and terminates in Willey Point. This area was first sighted by Ernest Shackleton's Southern Journey Party in December 1908. The spur was named by the Advisory Committee on Antarctic Names for William J. Gealy, a stratigrapher with the Ohio State University Geological Expedition of 1969–70, who worked the spur and found tetrapod fossils here.
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Carroll considered them closer to reptiles than the seymouriamorphs, but not as close as the diadectomorphs. Many phylogenetic analyses since Carroll (1995) agreed with his interpretation, including Laurin & Reisz (1997), Anderson (2001), and Ruta et al. (2003). A few have still considered lepospondyls ancestral to amphibians, but came to this conclusion without changing the position of lepospondyls compared to seymouriamorphs and diadectomorphs. Lepospondyl and tetrapod classification is still controversial, and even recent studies have had doubts about lepospondyl monophyly.
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The tetrapod's ancestral fish, tetrapodomorph, possessed similar traits to those inherited by the early tetrapods, including internal nostrils and a large fleshy fin built on bones that could give rise to the tetrapod limb. To propagate in the terrestrial environment, animals had to overcome certain challenges. Their bodies needed additional support, because buoyancy was no longer a factor. Water retention was now important, since it was no longer the living matrix, and could be lost easily to the environment.
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A more comprehensive review of Red Hill "tetrapod" fossils was undertaken by Daeschler, Clack, and Shubin in 2009. They noted that most fossils were assigned to Hynerpeton based on their close proximity to the point where the original endochondral shoulder girdle was discovered. However, they argued that, since there were other unique animals (i.e. Densignathus, the owner of the unusual humerus, and whatcheerids) close to this point, proximity was not a sufficient reason to consider these referrals valid.
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Captorhinus aguti found at Richards Spur Richards Spur is a Permian fossil locality located at the Dolese Brothers Limestone Quarry north of Lawton, Oklahoma. The locality preserves clay and mudstone fissure fills of a karst system eroded out of Ordovician limestone and dolostone. Fossils of terrestrial animals are abundant and well-preserved, representing one of the most diverse Paleozoic tetrapod communities known. A common historical name for the site is Fort Sill, in reference to the nearby military base.
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Elginerpeton is a genus of stegocephalian (stem-tetrapod), the fossils of which were recovered from Scat Craig, Scotland, in rocks dating to the late Devonian Period (Late Frasnian stage, 375 million years ago). The only known fossil has been given the name Elginerpeton pancheni. Elginerpeton is known from skeletal fragments including a partial shoulder and hip, a femur, tibia (lower hind limb), and jaw fragments. The holotype is a lower jaw fragment estimated at 40 centimeters in total length.
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The two major hypotheses for lissamphibian origins are that they are either descendants of dissorophoid temnospondyls or microsaurian "lepospondyls". If the former (the "temnospondyl hypothesis") is true, then Reptiliomorpha includes all tetrapod groups that are closer to amniotes than to temnospondyls. These include the diadectomorphs, seymouriamorphs, most or all "lepospondyls", gephyrostegids, and possibly the embolomeres and chroniosuchians. In addition, several "anthracosaur" genera of uncertain taxonomic placement would also probably qualify as reptiliomorphs, including Solenodonsaurus, Eldeceeon, Silvanerpeton, and Casineria.
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In 2014, fossils of an indeterminate species of Tanystropheus were discovered in the Wolfville Formation in the Bay of Fundy in Nova Scotia, Canada.Stratigraphic and Temporal Context and Faunal Diversity of Permian-Jurassic Continental Tetrapod Assemblages from the Fundy Rift Basin, Eastern Canada. Hans-Dieter Sues and Paul E. Olsen. Atlantic Geology 51; 2015; 139-205 Indeterminate Tanystropheus remains are also known from the Jilh Formation of Saudi Arabia and various Anisian-Ladinian sites in Spain, Italy, and Switzerland.
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Whatcheeriidae is an extinct family of tetrapods which lived in the Mississippian sub-period, a subdivision of the Carboniferous period. It contains the genera Pederpes, Whatcheeria, and possibly Ossinodus. Fossils of a possible whatcheeriid have been found from the Red Hill locality of Pennsylvania. If these remains are from a whatcheeriid, they extend the range of the family into the Late Devonian and suggest that advanced tetrapods may have lived alongside primitive tetrapod ancestors like Hynerpeton and Densignathus.
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The first tetrapods probably evolved in coastal and brackish marine environments, and in shallow and swampy freshwater habitats. Formerly, researchers thought the timing was towards the end of the Devonian. In 2010, this belief was challenged by the discovery of the oldest known tetrapod tracks, preserved in marine sediments of the southern coast of Laurasia, now Świętokrzyskie (Holy Cross) Mountains of Poland. They were made during the Eifelian stage at the end of the Middle Devonian.
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The Devonian period 419–359 Ma (Age of Fishes) saw the development of early sharks, armoured placoderms and various lobe-finned fishes including the tetrapod transitional species The evolution of fish began about 530 million years ago during the Cambrian explosion. It was during this time that the early chordates developed the skull and the vertebral column, leading to the first craniates and vertebrates. The first fish lineages belong to the Agnatha, or jawless fish. Early examples include Haikouichthys.
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Elpistostegalia or Panderichthyida is an order of prehistoric lobe-finned fishes which lived during the Late Devonian period (about 385 to 374 million years ago).Elpistostegidae on the Taxonomicon They represent the advanced tetrapodomorph stock, the fishes more closely related to tetrapods than the osteolepiform fishes. The earliest elpistostegalians, combining fishlike and tetrapod-like characters, are sometimes called fishapods, a phrase coined for the advanced elpistostegalian Tiktaalik. Through a strict cladistic view, the order includes the terrestrial tetrapods.
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There are faint furrows at the sutures that enclose these tubes. The tubes, which are presumably venom canals, end at discharge orifices near the tip of the crown. MNA V3680 is the earliest example of a tetrapod with completely enclosed tooth canals for the delivery of oral toxins, which are seen today in elapid snakes. MNA V3680, along with several other teeth from the Cumnock Formation near Raleigh, North Carolina, represent a second species of Uatchitodon, U. schneideri.
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Most tetrapod species possess a larynx, but its structure is typically simpler than that found in mammals. The cartilages surrounding the larynx are apparently a remnant of the original gill arches in fish, and are a common feature, but not all are always present. For example, the thyroid cartilage is found only in mammals. Similarly, only mammals possess a true epiglottis, although a flap of non-cartilagenous mucosa is found in a similar position in many other groups.
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When certain traits are emphasized through implied weighting, Eucritta is connected to baphetids as part of a branch immediately basal to crown-Tetrapoda. A 2009 restudy of Baphetes assigned the name Baphetoidea to the branch incorporating baphetids, Eucritta, and the unusual filter-feeding stem tetrapod Spathicephalus. Ruta and Coates' 2007 revision of their earlier analysis further supported this position next to baphetids and basal to crown-Tetrapoda. Many subsequent studies have cemented this position, although some instability still exists.
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2013)), and temperature control (Clack 2007, as cited by (Hohn-Schulte et al. 2013))—implying that organisms developing limbs were also adapting to spending some of their time out of water. However, studies have found that sarcopterygians developed tetrapod-like limbs suitable for walking well before venturing onto land (King 2011, as cited by (Pierce et al. 2012)); this suggests they adapted to walking on the ground-bed under water before they advanced onto dry land.
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The first tetrapodomorphs, which included the gigantic rhizodonts, had the same general anatomy as the lungfish, who were their closest kin, but they appear not to have left their water habitat until the late Devonian epoch (385–359 Ma), with the appearance of tetrapods (four- legged vertebrates). Tetrapods are the only tetrapodomorphs which survived after the Devonian. Non-tetrapod sarcopterygians continued until towards the end of Paleozoic era, suffering heavy losses during the Permian–Triassic extinction event (251 Ma).
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Tinirau is an extinct genus of sarcopterygian fish from the Middle Devonian of Nevada. Although it spent its entire life in the ocean, Tinirau is a stem tetrapod close to the ancestry of land-living vertebrates in the crown group Tetrapoda. Relative to more well-known stem tetrapods, Tinirau is more closely related to Tetrapoda than is Eusthenopteron, but farther from Tetrapoda than is Panderichthys. The type and only species of Tinirau is T. clackae, named in 2012.
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A study from 1993 found dinosaur specimens to comprise only 6% of the total tetrapod sample; subsequent discoveries increased this number to approximately 11% of all findings. Carnivorous dinosaurs are the most common terrestrial carnivores of the Ischigualasto Formation, with herrerasaurids comprising 72% of all recovered terrestrial carnivores. The carnivorous archosaur Herrerasaurus is the most numerous of these dinosaur fossils. Another important putative dinosaur with primitive characteristics is Eoraptor lunensis, found in Ischigualasto in the early 1990s.
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Restoration of P. rhombolepis As an intermediate in the fish-tetrapod evolution, Panderichthys had the capacity to breathe air. The trend from the early sarcopterygians to the first tetrapods was an increase in the size of the spiracular chamber and its opening to the outside. Compared to Eusthenopteron, the spiracular chamber of Panderichthys is greatly expanded and the hyomandibula is shorter compared to those in fish. The opercular series was also shorter compared to other osteolepiforms.
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The skull of a bowfin (Amia calva), one of the most basal living actinopterygiians. Skull bones are labelled based on tetrapod homologies. Watson & Day (1916)'s "orthodox" interpretation of fish skulls argued that fish lacked independent postparietals, with the elongated paired midline bones at the back of the skull being interpreted as parietals. On the other hand, Westoll (1938) proposed an alternative interpretation which identified the bones as postparietals based on comparisons between early tetrapods and their sarcopterygian ancestors.
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A diverse assortment of palaeoniscoid fish teeth and scales and bivalve shells are by far the most abundant fossils. Worm burrows and ostracods are also very common. Tetrapod remains include Dimetrodon teeth, unusually small "Lysorophus" (Brachydectes) vertebrae, skull fragments from small Diplocaulus and Trimerorhachis, a few Eryops components, and fragments from various microsaurs, possibly referable to Pantylus, Microbrachis, and/or Pelodosotis. Most of the bones belong to small animals, likely due to taphonomic bias due to ease of transportation.
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An example of Beaker pottery from the Necropolis of Anghelu Ruju Tetrapod vase, Necropolis of Santu Pedru The Beaker culture in Sardinia appeared circa 2100 BC during the last phase of the Chalcolithic period. It initially coexisted with and then replaced the previous Monte Claro culture in Sardinia, developing until the ancient Bronze Age circa 1900-1800 BC. Then, the Beaker culture mixed with the related Bonnanaro culture, considered the first stage of the Nuragic civilization.
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Following Jaekel's hypothesis, Robert Broom used Scincosaurus as a representative of microsaurs during his 1921 study on tetrapod ankle bones. As the 20th century proceeded, Scincosaurus fell into obscurity. However, by the 1960s sources which did discuss it once again considering it a member of Nectridea outside of Microsauria. During his 1963 monograph on the advanced diplocaulid Diploceraspis, J.R. Beerbower placed Scincosaurus as a basal diplocaulid closely related to Batrachiderpeton in a subfamily he called Batrachiderpetoninae.
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Research in mammals has implicated hypoxia inducible factor (HIF) as a key regulator of gene expression changes in response to hypoxia However, a direct link between fish HIFs and gene expression changes in response to hypoxia has yet to be found. Phylogenetic analysis of available fish, tetrapod, and bird HIF-α and -β sequences shows that the isoforms of both subunits present in mammals are also represented in fish Within fish, HIF sequences group close together and are distinct from tetrapod and bird sequences. As well, amino acid analysis of available fish HIF-α and -β sequences reveals that they contain all functional domains shown to be important for mammalian HIF function, including the basic helix-loop- helix (bHLH) domain, Per-ARNT-Sim (PAS) domain, and the oxygen-dependent degradation domain (ODD), which render the HIF-α subunit sensitive to oxygen levels. The evolutionary similarity between HIF sequences in fish, tetrapods and birds, as well as the conservation of important functional domains suggests that HIF function and regulation is similar between fish and mammalian species.
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Adaptations to arboreal lifestyle are understood to evolve through convergent evolution. However, many arboreal vertebrates share similar physical mechanisms (grasping, clinging, hooking)Hildebrand, M. & Goslow, G. E. J. 2001 Analysis of vertebrate structure, 5th edn. New York, NY: John Wiley & Sons. Suminia is referred to as the earliest known arboreal tetrapod due to the suggested grasping abilities inferred from the notably enlarged and phalangiform carpal 1 and tarsal 1 which indicate that they possess a divergent first digit, capable of grasping.
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For example, a 2007 paper has suggested that adelospondyls are stem-tetrapods close to colosteids and a 2017 paper on Lethiscus has Aïstopoda in the tetrapod stem based on their primitive braincase. These studies differ in the internal and external relationships of the remaining lepospondyl taxa. The former places the remaining lepospondyls into a single clade along the amniote stem. The latter does not treat the relationships of nectrideans or adelospondyls, but finds microsaurs to be early amniotes, and places lysorophians within microsaurs.
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Ichthyostega, 374–359 Ma Tetrapod-like vertebrates first appeared in the early Devonian period. These early "stem- tetrapods" would have been animals similar to Ichthyostega, with legs and lungs as well as gills, but still primarily aquatic and unsuited to life on land. The Devonian stem-tetrapods went through two major bottlenecks during the Late Devonian extinctions, also known as the end-Frasnian and end- Fammenian extinctions. These extinction events led to the disappearance of stem-tetrapods with fish-like features.
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Tetrapod skin would have been effective for both absorbing oxygen and discharging CO2, but only up to a point. For this reason, early tetrapods may have experienced chronic hypercapnia (high levels of blood CO2). This is not uncommon in fish that inhabit waters high in CO2. According to one hypothesis, the "sculpted" or "ornamented" dermal skull roof bones found in early tetrapods may have been related to a mechanism for relieving respiratory acidosis (acidic blood caused by excess CO2) through compensatory metabolic alkalosis.
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However, this type of locomotion is not rigid and insects can adapt a variety of gaits. For example, when moving slowly, turning, avoiding obstacles, climbing or slippery surfaces, four (tetrapod) or more feet (wave- gait) may be touching the ground. Insects can also adapt their gait to cope with the loss of one or more limbs. Cockroaches are among the fastest insect runners and, at full speed, adopt a bipedal run to reach a high velocity in proportion to their body size.
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Restoration of Elginerpeton In Elginerpeton pancheni, a prototetrapod from the late Frasnian, basic tetrapod characteristics in the lower jaw and the cranium are observed. The taxon is believed to fill the gap between elpistostegalid fishes and well-preserved Devonian tetrapods. The Elginerpeton is considered more derived than the elpistostegalid fishes due to presence of paired fangs on the parasymphysial toothplate, a slender shaped anterior coronoid, and in the loss of the intracranial joint and coronoid fossa.Ahlberg, P. E., & Clack, J. A. (1998).
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Caltrops were used extensively and effectively during World War II. The modifications and variants produced by the Special Operations Executive (SOE) and the Office of Strategic Services (OSS) of the United States are still in use today within special forces and law enforcement bodies. The Germans dropped crowsfeet. These were made from two segments of sheet metal welded together into a tetrapod with four barbed points and then painted in camouflage colours. They came in two sizes with a side length of either .
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The holotype specimen of Tambachia trogallas, known as MNG 7722, has been found from an outcrop of the Tambach Formation at the Bromacker locality in the Thuringian Forest of central Germany. It consists of a skull and much of the postcranial skeleton. The only major portion of the skeleton that is missing is the presacral vertebral column. The Bromacker locality is a sandstone quarry that is well known for tetrapod trackways and articulated skeletons of terrestrial and semiterrestrial amphibians and reptiles.
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The type species, Ekrixinatosaurus novasi, was first described in 2004 by Argentinian paleontologist Jorge Calvo, and Chilean paleontologists David Rubilar-Rogers and Karen Moreno. The fossils were found dispersed over an area of 15m in the Candeleros Formation, a geologic formation that outcrops in Río Negro, Neuquén, and Mendoza provinces of Argentina. This formation dates from 100-97 mya.,Leanza, H.A.; Apesteguia, S.; Novas, F.E. & de la Fuente, M.S. (2004): Cretaceous terrestrial beds from the Neuquén Basin (Argentina) and their tetrapod assemblages.
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Acanthostega is the earliest example of a digitized tetrapod. The humerus and femur of Acanthostega contain evidence of greater development of the appendicular muscles compared to more aquatic tetrapods. Acanthostega has a total lack of dermal fin rays and displays the presence of two or more spool- shaped bones or cartilages articulating individually in antero-posterial sets on the distal end of its limbs. This feature can now be distinguished as digits instead of the endoskeletal radials seen in earlier tetrapods.
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Gogonasus (meaning "snout from Gogo") was a lobe-finned fish known from three- dimensionally preserved 380-million-year-old fossils found from the Gogo Formation in Western Australia. It lived in the Late Devonian period, on what was once a 1,400-kilometre coral reef off the Kimberley coast surrounding the north-west of Australia. Gogonasus was a small fish reaching 30–40 cm (1 ft) in length. Its skeleton shows several features that were like those of a four- legged land animal (tetrapod).
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The original 1994 description of Hynerpeton tentatively placed it within the order Ichthyostegalia of the superclass Tetrapoda. At the time, "Tetrapoda" referred to any four-limbed vertebrate and "Ichthyostegalia" referred to "primitive", Ichthyostega-like Devonian members of the category. However, the arrival and popularity of cladistics has altered both of these terms. The cladistic definition of "tetrapod" now popular among biologists and paleontologists refers to a clade (relations-based grouping) containing only descendants of the last common ancestor of living tetrapods.
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The thorax or chest is a part of the anatomy of humans, mammals, other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the creature's body, each of which is in turn composed of multiple segments. The human thorax includes the thoracic cavity and the thoracic wall. It contains organs including the heart, lungs, and thymus gland, as well as muscles and various other internal structures.
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Amphibians and reptiles were strongly affected by the Carboniferous rainforest collapse (CRC), an extinction event that occurred ~307 million years ago. The Carboniferous period has long been associated with thick, steamy swamps and humid rainforests. Since plants form the base of almost all of Earth's ecosystems, any changes in plant distribution have always affected animal life to some degree. The sudden collapse of the vital rainforest ecosystem profoundly affected the diversity and abundance of the major tetrapod groups that relied on it.
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The Middle Paddock site, where the Ossinodus specimen were collected, is organized as a "progradational deltaic system," meaning that there is an upper layer with sedimentary patterns exhibiting cyclic flood plains, encompassing a fluvial environment. The lower layer contains alternating layers of wave- influenced siltstone, sandstone, and limestone. Uncovered at the site were also various aquatic fossils, again further suggesting that this early tetrapod coexisted with aquatic species. The aquatic fauna that were recovered at the site includes lungfish and sharks.
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Andersonerpeton is an extinct genus of aïstopod from the Bashkirian (early Pennsylvanian) of Nova Scotia, Canada. It is known from a single jaw, which shares an unusual combination of features from both other aistopods and from stem-tetrapod tetrapodomorph fish. As a result, Andersonerpeton is significant for supporting a new classification scheme which states that aistopods evolved much earlier than previously expected. The genus contains a single species, A. longidentatum, which was previously believed to have been a species of the microsaur Hylerpeton.
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Anolis is a genus of anoles (), iguanian lizards in the family Dactyloidae, native to the Americas. With more than 425 species, it represents the world's most species-rich amniote tetrapod genus, although it has been proposed that many of these should be moved to other genera, in which case only about 45 Anolis species remain. Abstract Previously, it was classified under the family Polychrotidae that contained all the anoles as well as Polychrus, but recent studies place it under Dactyloidae.
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The KRAB domain had initially been identified in 1988 as a periodic array of leucine residues separated by six amino acids 5’ to the zinc finger region of KOX1/ZNF10 coined heptad repeat of leucines (also known as a leucine zipper) . Later, this domain was named in association with the C2H2-Zinc finger proteins Krüppel associated box (KRAB). The KRAB domain is confined to genomes from tetrapod organisms. The KRAB containing C2H2-ZNF genes constitute the largest sub-family of zinc finger genes.
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Sarcopterygii (; from Greek , flesh, and , fin)—sometimes considered synonymous with Crossopterygii ("fringe-finned fish", from Greek , fringe)—is a clade (traditionally a class or subclass) of the bony fish whose members are known as lobe-finned fish. The group Tetrapoda, a superclass including amphibians, reptiles (including dinosaurs and therefore birds), and mammals, evolved from certain sarcopterygians; under a cladistic view, tetrapods are themselves considered a group within Sarcopterygii. The living non-tetrapod sarcopterygians include two species of coelacanths and six species of lungfish.
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Each segment is connected to the structure of the telescope through four actuators, allowing to have an active reflecting primary surface. As well, each segment is formed by eight precision electro-formed nickel sub-panels. The reflecting secondary surface (M2) has a 2.6m diameter, also built by nine electro-formed nickel sub-panels, and is attached to the telescope with an active hexapod that allows precise focus, lateral offsets and tilts. The hexapod is attached to the telescope through a metal tetrapod.
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It lacks the dorsal and anal fins (fish fin) and its tail is more like those of early tetrapods than the caudal fins of other lobe-fins. The shoulders exhibits several tetrapod-like features, while the humerus is longer than those found in other lobe-fins. The vertebral column is ossified throughout its length and the vertebrae are comparable to those of early tetrapods. On the other hand, the distal parts of the front fins are unlike those of tetrapods.
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The humerus of Panderichthys is more derived than that of Tiktaalik because of the presence of a more preaxially oriented radial facet as well as a more slender shaft. One feature that is unique to Panderichthys is that the entepicondyle does not project as far as the epipodial facets and the humeral ridge does not go into the entepicondyle.Boisvert, Catherine A. "The humerus of Panderichthys in three dimensions and its significance in the context of the fish–tetrapod transition." Acta Zoologica90.
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HOXD13 is the first of several HOXD genes located in a cluster on chromosome 2. Deletions that remove the entire HOXD gene cluster or the 5' end of this cluster have been associated with severe limb and genital abnormalities. The product of the mouse Hoxd13 gene plays a role in axial skeleton development and forelimb morphogenesis. Changes in the expression of the Hoxd13 gene in early lobe-finned fish may have also contributed to the evolution of the tetrapod limb.
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With the close of the Carboniferous, the amniotes became the dominant tetrapod fauna. While primitive, terrestrial reptiliomorphs still existed, the synapsid amniotes evolved the first truly terrestrial megafauna (giant animals) in the form of pelycosaurs, such as Edaphosaurus and the carnivorous Dimetrodon. In the mid- Permian period, the climate became drier, resulting in a change of fauna: The pelycosaurs were replaced by the therapsids.Colbert, E.H. & Morales, M. (2001): Colbert's Evolution of the Vertebrates: A History of the Backboned Animals Through Time.
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Recessive alleles of some genes involved in embryonic limb patterning produce bilateral diplopodia, and diplopodia can be experimentally induced in early embryos. Many instances of diplopodia in humans have no apparent cause. People have been able to produce diplopod limbs by increasing sonic hedgehog (shh) signaling in the limb buds of embryos. The zone of polarizing activity (ZPA) in the proximal posterior mesoderm of a tetrapod limb bud is responsible for maintaining the anterior- posterior axis of the growing limb.
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Asaphestera is an extinct genus of a tetrapod described on the basis of fossils from the Carboniferous of the Joggins locality in Nova Scotia, Canada. It was originally described as an undetermined lepospondyl and subsequently classified as a microsaur within the family Tuditanidae. A study published in May 2020 found that specimens referred to Asaphestera represented several unrelated species. Steen (1934)'s original species name Asaphestera platyris was retained for a skull which has been re-evlatuated as the earliest known synapsid.
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Ventastega curonica belongs to Tetrapoda in accordance with the traditional definition. According to a strict parsimony phylogeny that ranked 319 characters of tetrapods (defined less inclusively as a crown group) and other tetrapodomorphs, Ventastega is part of the stem- tetrapod group, with 96% bootstrapping consensus at its node (shown below). The group of stem-tetrapods contains any extinct taxon that, according to morphological analysis, is more closely related to lissamphibians (living amphibians) and amniotes than to any other crown group.
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Rotaurisaurus is an extinct genus of amphibian-grade tetrapod from the family Lapillopsidae. This genus is known only from an incomplete crushed skull and associated left jaw, together given the designation UTGD (University of Tasmania Geological Department) 87795. The generic name, Rotaurisaurus, is a combination of Latin words translating to "circle-eared lizard". This references the shape of its otic notches, which acquire a circular form due to being partially enclosed by the tabular bones at the back of the skull.
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Pneumatic structures of "Angloposeidon" "Angloposeidon" is the informal name given to a sauropod dinosaur from the Early Cretaceous Wessex Formation of the Isle of Wight in southern England. It was a possible brachiosaurid but has not been formally named. Darren Naish, a notable vertebrate palaeontologist, has worked with the specimen and has recommended that this name only be used informally and that it not be published. However, he published it himself in his book Tetrapod Zoology Book One from 2010.
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It was inferred that these structures found in Brasilitherium performed the same roles in modern mammals; specifically, the anterior overlying tissue warmed incoming odorants and the posterior portion was responsible for picking up scent. The complex latter section of the nasal structure suggests that Brasilitherium had a well-developed sense of smell. The same studies also found a hollow across the secondary plate, implicating the presence of the Jacobson’s organ. These observations suggest that this organism possessed features that connect both its tetrapod ancestors and later mammalians.
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Adelospondyls have been assigned to a variety of groups in the past. They have traditionally been seen as members of the subclass Lepospondyli, related to other unusual early tetrapods such as "microsaurs", "nectrideans", and aïstopods. Analyses such as Ruta & Coates (2007) have offered an alternate classification scheme, arguing that adelospondyls were actually far removed from other lepospondyls, instead being stem-tetrapod stegocephalians closely related to the family Colosteidae. Most adelospondyls belong to the family Adelogyrinidae, and prior to 2003 the order and family were considered synonymous.
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Living in the rich biosphere of Africa south of the Sahara, the Nile crocodile may come into contact with multiple other large predators. Its place in the ecosystems it inhabits is largely unique, as it is the only large tetrapod carnivore that spends the majority of its life in water and hunting prey associated with aquatic zones. Large mammalian predators in Africa are often social animals and obligated to feed almost exclusively on terrestrial zones. The Nile crocodile is a strong example of an apex predator.
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Large, plate-like zygapophyses (joints between vertebrae) are also present, along with diapophyses and forward-pointing parapophyses (different types of rib joints at the side and front of each vertebra, respectively). On the other hand, this genus completely lacks intercentra, small bones wedged between the centra of each vertebra in some tetrapod groups. Most of the dorsal ribs are long and project outwards and backwards, except for the last 3 which are short and point slightly forwards. Three rows of long gastralia (belly ribs) are also present.
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Longlure frogfish realigning its jaw Frogfishes generally do not move very much, preferring to lie on the sea floor and wait for prey to approach. Once the prey is spotted, they can approach slowly using their pectoral and pelvic fins to walk along the floor. They rarely swim, preferring to clamber over the sea bottom with their fins in one of two "gaits". In the first, they alternately move their pectoral fins forward, propelling themselves somewhat like a two- legged tetrapod, leaving the pelvic fins out.
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Speculative restoration of Concavenator with a hump as a hypothetical thermoregulatory device Restoration of the crushed skull Some amount of skepticism has been raised among experts on the validity of the interpretation that the ulnar bumps represent quill knobs. Darren Naish, of the blog Tetrapod Zoology, speculated that the bumps would have been unusually far up and irregularly spaced for quill knobs. He additionally pointed out that many animals have similar structures along intermuscular lines that act as tendon attachment points among other things.Naish, D. (2010).
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Sinoconodon rigneyiPaleofile.com (net, info) . is an ancient mammaliamorph or early mammal (depending on systematic approach) that appears in the fossil record of the Lufeng Formation of China in the Sinemurian stage of the Early Jurassic period, about 193 million years ago. While in many traits very similar to non-mammalian synapsids, it possessed a special, secondarily evolved jaw joint between the dentary and the squamosal bones, which had replaced the primitive tetrapod one between the articular and quadrate bones, a trait commonly used to define mammals.
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Swedish paleontologist Erik Jarvik, a member of the 1947 expedition, could not assign the skull to either Ichthyostega or Acanthostega. In 1988, English paleontologist Jennifer Clack was the first to propose that the material represented a third type of tetrapod from Greenland, based mainly on the teeth. While the skull shape is closest to Ichthyostega, the teeth are smaller, more numerous and less curved, indicating the two exploited different foods. The surface ornamentation on the skull bones are less pronounced, indicating lighter dermal armour.
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Robert Rafael Reisz is a Canadian paleontologist and specialist in the study of early amniote and tetrapod evolution. Robert Reisz was born August 27, 1947, in Oradea, Romania. He received his B.Sc. (1969), M.Sc. (1971) and Ph.D. (1975) from McGill University as Robert L. Carroll's first doctoral graduate. After teaching as visiting lecturer at University of California, Los Angeles for a year, he accepted an appointment in the Biology Department at the University of Toronto's Mississauga Campus in 1975 where he still maintains his research lab.
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The uniquely foldable teeth indicate that Andersonerpeton is an aistopod, as these teeth are also seen in Coloraderpeton and Oestocephalus, but no other tetrapods until the appearance of snakes in the Cretaceous period. In addition, the mandible was smooth and wide, similar to that of most aistopods. However, in many other features the jaw of Andersonerpeton closely resembles early tetrapod relatives such as Elginerpeton. These include the arrangement of teeth and denticles on the parasympheseal and coronoid bones, as well as labyrinthine marginal teeth.
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The species Plesiosaurus megadeirus was coined for two partial postcranial specimens in a publication cataloging Mesozoic tetrapod specimens in the collections of the Sedgwick Museum of Earth Sciences at the University of Cambridge.H. G. Seeley. 1869. Index to the Fossil Remains of Aves, Ornithosauria, and Reptilia, from the Secondary System of Strata, Arranged in the Woodwardian Museum of the University of Cambridge. Deighton, Bell, and Co, Cambridge 1-143 The name Pliosaurus portlandicus was coined for a partial hindlimb from Dorset,R. Owen. 1869.
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In addition, he is involved in the TW:eed Project (Tetrapod World: early evolution and diversity), and in investigating the Jurassic vertebrates of the Isle of Skye. Throughout his career, Fraser has been involved in a number of excavations worldwide including sites in China, Europe, and North America. He has completed 10 seasons of excavation at the Morrison Formation in Wyoming, USA. He helped name Amotosaurus, a tanystropheid protorosaur from the Middle Triassic in Germany; Fuyuansaurus, a protorosaur reptile from the Middle Triassic in China; and Eobalaenoptera.
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The Cynognathus Assemblage Zone is a tetrapod assemblage zone or biozone which correlates to the Burgersdorp Formation of the Beaufort Group, a fossiliferous and geologically important geological Group of the Karoo Supergroup in the Karoo Basin of South Africa. The thickest outcrops of this biozone, reaching approximately , occur between Queenstown and Lady Frere in the Eastern Cape. Outcrops then thin out to between around Aliwal North, Burgersdorp, Steynsburg, and Rouxville. Thin outcrops are also found in areas in the Free State that border Lesotho.
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The holotype specimen of Bystrowisuchus was found near the eastern banks of the Don River in Ilovlinsky District, Volgograd Oblast. It came from a fossil site known as the Donskaya Luka locality, which preserves a wide diversity of Early Triassic tetrapod fossils. Along with Bystrowisuchus, the Donskaya Luka fossil assemblage includes temnospondyl amphibians, a chroniosuchian, a procolophonid, a sauropterygian, a protorosaurian, possible trilophosaurid archosauromorphs, two rauisuchid archosaurs, and a dicynodont. Elongated neural spines previously attributed to the rauisuchid Scythosuchus basileus may belong instead to Bystrowisuchus.
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In 1993 an undergraduate geology student discovered fossilised tetrapod trackways, footprints preserved in Devonian rocks, on the north coast of the island at Dohilla (). About 385 million years ago, a primitive vertebrate passed near a river margin in the sub-equatorial river basin that is now southwestern Ireland and left prints in the damp sand. The prints were preserved by silt and sand overlying them, and were converted to rock over geological time. The Valentia Island trackways are among the oldest signs of vertebrate life on land.
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Restoration of Bradysaurus Pareiasaurs ranged in size from long, and may have weighed up to . They were stocky, with short tails, small heads, robust limbs, and broad feet. The cow-sized species Bunostegos, which lived 260 million years ago, is the earliest known example of a tetrapod with a fully erect posture as its legs were positioned directly under its body.Pre- reptile may be earliest known to walk upright on all fours Pareiasaurs were protected by bony scutes called osteoderms that were set into the skin.
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The only known specimen of Microleter is a well-preserved skull and lower jaw designated as OMNH 71306, the holotype specimen. It was found at the Dolese Brothers limestone quarry near Richards Spur in Comanche County, Oklahoma. Historically referred to as the Fort Sill locality, the quarry has preserved Early Permian (Artinskian, ~289-286 Ma) fissure fills in an Ordovician cave system. The fissure fills have yielded many other well preserved tetrapod fossils, including the most diverse assortment of Permian parareptiles in North America.
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Spondylerpeton is an extinct genus of tetrapod closely related to "Cricotus" (Archeria) in the family Archeriidae. This genus is known from fragmentary remains, namely a short series of tail vertebrae preserved in an ironstone nodule. These remains were found in the Mazon Creek beds of Illinois, an area famed for its preservation of Carboniferous plants and animals. Spondylerpeton individuals were probably about three to four feet in length, by far the largest animals known to have inhabited the Mazon Creek area during this era.
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Taxonomists who subscribe to the cladistic approach include the grouping Tetrapoda within this group, which in turn consists of all species of four-limbed vertebrates. The fin-limbs of lobe-finned fishes such as the coelacanths show a strong similarity to the expected ancestral form of tetrapod limbs. The lobe-finned fishes apparently followed two different lines of development and are accordingly separated into two subclasses, the Rhipidistia (including the Dipnoi, the lungfish, and the Tetrapodomorpha which include the Tetrapoda) and the Actinistia (coelacanths).
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The legs of tetrapods, the main group of terrestrial vertebrates, have internal bones, with externally attached muscles for movement, and the basic form has three key joints: the shoulder joint, the knee joint, and the ankle joint, at which the foot is attached. Within this form there is much variation in structure and shape. An alternative form of vertebrate 'leg' to the tetrapod leg is the fins found on amphibious fish. Also a few tetrapods, such as the macropods, have adapted their tails as additional locomotory appendages.
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Embryonic pharyngeal slits, which form in many animals when the thin branchial plates separating pharyngeal pouches and pharyngeal grooves perforate, open the pharynx to the outside. Pharyngeal arches appear in all tetrapod embryos: in mammals, the first pharyngeal arch develops into the lower jaw (Meckel's cartilage), the malleus and the stapes. Haeckel produced several embryo drawings that often overemphasized similarities between embryos of related species. Modern biology rejects the literal and universal form of Haeckel's theory, such as its possible application to behavioural ontogeny, i.e.
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As would be expected from a fin, there are numerous lepidotrichia (long and thin fin rays). Panderichthys has many features that can be considered an intermediate form during the fish-tetrapod evolution and displays some features that are more derived than its phylogenetic position indicates, while others that are more basal. The body form of Panderichthys and Tiktaalik represents a major step in the transition from fish to tetrapods and they were even able to haul out on land.Ahlberg, Per Erik, and Jennifer A. Clack.
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An adult salamander generally resembles a small lizard, having a basal tetrapod body form with a cylindrical trunk, four limbs, and a long tail. Except in the family Salamandridae, the head, body, and tail have a number of vertical depressions in the surface which run from the mid-dorsal region to the ventral area and are known as costal grooves. Their function seems to be to help keep the skin moist by channeling water over the surface of the body. Sirens have an eel-like appearance.
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Though there is little certainty in how Stanocephalosaurus breathed, paleontologists suggest that it had air pockets around the stapes, which have been hypothesized to act as resonance chambers, meaning that the inner ear bone could be related to underwater hearing. This trait is possibly associated with early tetrapod evolution. S. amenasensis show a circumorbital canal that runs along the prefrontal, postorbital and jugal, and a supraanarial canal that runs along the nasal and anterior half of the prefrontal. These dermo-sensory grooves suggest an aquatic lifestyle.
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At the time, Spathicephalus and other tetrapods from the Namurian of Scotland were some of the oldest tetrapods known, predating the better-known Late Carboniferous tetrapod assemblages of the British Coal Measures. In November 1974, Scottish paleontologist Stanley P. Wood discovered additional skull and jaw fragments of Spathicephalus in an open-pit mine (the Dora Open Cast Mine) near the town of Cowdenbeath in Fife. Wood found these fossils in a layer of siltstone that is the same age as the ironstone in Loanhead. Sydney Harbor.
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Various pieces of evidence suggest tetrapod mass mortality was the cause of death in the Chañares Formation. Fossils of both young and adult specimens were found at this locale, and these are not limited to Probainognathus, but rather represent many taxa that fell victim to the event. There is also an unusual concentration of herbivores, carnivores, and omnivores in this formation. Numerous fossils of each type were found in close proximity to one another, despite the fact that this intermingling would normally be uncommon.
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Remains have exclusively been recovered from a single carbonaceous shale near the top of the Late Devonian, Famennian, Witpoort Formation (Witteberg Group) exposed in a road cutting south of Makhanda/Grahamstown in South Africa. This site, the Waterloo Farm lagerstätte is interpreted as representing a back barrier coastal lagoonal setting with both marine and fluvial influences. Gess, Robert W.; Whitfield, Alan K. (14 February 2020). "Estuarine fish and tetrapod evolution: insights from a Late Devonian (Famennian) Gondwanan estuarine lake and a southern African Holocene equivalent".
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Similarly to humans, whales and dolphins have experienced an independent loss of functional OR genes. This is demonstrated by the organism's return to an aquatic environment, subsequently experiencing a loss of terrestrial olfactory register. Olfactory senses are generally more heightened for a terrestrial species than for an aquatic, as airborne volatiles are more important to detect than water-soluble scents in land animals. Support for this theory is exemplified through the fish-to-tetrapod transition, where animals began to populate terrestrial niches and a tremendous expansion of the olfactory system can be observed.
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The Yanoconodon holotype is so well preserved that scientists were able to examine tiny bones of the middle ear. These are of particular interest because of their "transitional" state: Yanoconodon has fundamentally modern middle ear bones, but these are still attached to the jaw by an ossified Meckel's cartilage. This is a feature retained from earlier stem mammals, and illustrates the transition from a basal tetrapod jaw and ear, to a mammalian one in which the middle ear bones are fully separate from the jaw. Despite this feature Yanoconodon is a true mammal.
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In most recent studies of early tetrapod phylogeny, Cotylosauria is no longer recognized and Diadectomorpha is placed as the sister taxon of Amniota. However, while the majority of analyses now place diadectids outside Amniota, some have found them to be true amniotes. Most phylogenetic studies of the three diadectomorph families – Diadectidae, Limnoscelidae, and Tseajaiidae – have found diadectids and limnoscelids to be more closely related to each other than either is to Tseajaia. In other words, Diadectidae and Limnoscelidae form a clade within Diadectomorpha and Tseajaia is excluded from the clade.
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The evolution of early tetrapod respiration was influenced by an event known as the "charcoal gap", a period of more than 20 million years, in the middle and late Devonian, when atmospheric oxygen levels were too low to sustain wildfires. During this time, fish inhabiting anoxic waters (very low in oxygen) would have been under evolutionary pressure to develop their air-breathing ability. Early tetrapods probably relied on four methods of respiration: with lungs, with gills, cutaneous respiration (skin breathing), and breathing through the lining of the digestive tract, especially the mouth.
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In modern species that 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 they could only hear high intensity, low frequency sounds—and the stapes more probably just supported the brain case against the cheek. Only in the early Triassic, about hundred million years after they conquered land, did the tympanic middle ear evolve (independently) in all the tetrapod lineages.
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Procuhy is an extinct genus of dvinosaurian temnospondyl amphibian in the family Trimerorhachidae represented by the type species Procuhy nazariensis from the Early Permian of Brazil. It was named in 2015 on the basis of a partial skull from the lower part of the Pedra de Fogo Formation in Parnaíba Basin, which is about 278 million years old. It was likely an aquatic predator that inhabited lakes and wetland areas. During the Early Permian the center of tetrapod diversity was in the equatorial regions of the supercontinent Pangea, and Procuhy was part of this fauna.
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As with many Triassic temnospondyls, Callistomordax is considered to have been an aquatic freshwater tetrapod, evidenced by both its anatomy (e.g., lateral line system) and its depositional environment. The Lower Keuper Basin where Callistomordax was found was subjected to repeated transgression-regression cycles, resulting in mixed deposits of freshwater and marine taxa. Callistomordax is relatively rare and consists only of isolated elements in bonebeds with higher abundances of marine taxa, and the most complete specimens are found with various invertebrates and fish that suggest a relatively low salinity environment.
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The bones of its forearm, the radius and ulna, are very thin at the wrist and also unable to support it on land. It also lacks a sacrum and strong ligaments at the hip, which would be integral to supporting the animal against gravity. In this sense, the species is considered a tetrapod but not one that has adapted well enough to walk on land. Furthermore, its gill bars have a supportive brace characterized for use as an underwater ear because it can pick up noise vibrations through the water.
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Tetrapods that adapted to terrestrial living adapted these gill bones to pick up sounds through air, and they later became the middle ear bones seen in mammalian tetrapods. Ichthyostega, on the other hand, is considered to be a fully terrestrial tetrapod that perhaps depended on water for its aquatic young. Comparisons between the skeletal features of Acanthostega and Ichthyostega reveal that they had different habits. Acanthostega is likely exclusive to an aquatic environment, while Ichthyostega is progressed in the aquatic to terrestrial transition by living dominantly on the shores.
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Many recurring DNA sequences were recognized for newt Hox clusters, counting an enrichment of DNA transposon-like sequences similar to non-coding genomic fragments. Researchers found the results to suggest that Hox cluster expansion and transposon accumulation are common features of non-mammalian tetrapod vertebrates. After the loss of a limb, cells draw together to form a clump known as a blastema. This superficially appears undifferentiated, but cells that originated in the skin later develop into new skin, muscle cells into new muscle and cartilage cells into new cartilage.
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The lower jaw was S-shaped and divided into the subcylindrical transverse ramus, which contained the teeth, and the back ramus, which was more lightweight and was the location for most of the muscle attachments. The jaws also contained several fenestrae, including three that are not present in other sauropods. The front ends of the jaws had grooves that indicate the presence of a keratinous (horny) sheath. Nigersaurus is the only known tetrapod animal to have had jaws wider than the skull and teeth that extended laterally across the front.
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Of the tailless amphibians (the frogs and toads of the sub-class Anura) the majority are aquatic to an insignificant extent in adult life, but in that considerable minority that are mainly aquatic we encounter for the first time the problem of adapting the tailless-tetrapod structure for aquatic propulsion. The mode that they use is unrelated to any used by fish. With their flexible back legs and webbed feet they execute something close to the leg movements of a human 'breast stroke,' rather more efficiently because the legs are better streamlined.
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In order for the lungs to allow gas exchange, the lungs first need to have gas in them. In modern tetrapods, three important breathing mechanisms are conserved from early ancestors, the first being a CO2/H+ detection system. In modern tetrapod breathing, the impulse to take a breath is triggered by a buildup of CO2 in the bloodstream and not a lack of O2. A similar CO2/H+ detection system is found in all Osteichthyes, which implies that the last common ancestor of all Osteichthyes had a need of this sort of detection system.
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In contrast, reptiles - whose amniotic eggs have a membrane that enables gas exchange out of water, and which thereby can be laid on land - were better adapted to the new conditions. Reptiles invaded new niches at a faster rate and began diversifying their diets, becoming herbivorous and carnivorous, rather than feeding exclusively on insects and fish. Meanwhile, the severely impacted amphibians simply could not out-compete reptiles in mastering the new ecological niches, and so were obligated to pass the tetrapod evolutionary torch to the increasingly successful and swiftly radiating reptiles.
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The Pristerognathus Assemblage Zone is a tetrapod assemblage zone or biozone which correlates to the upper Abrahamskraal Formation and lowermost Teekloof Formation, Adelaide Subgroup of the Beaufort Group, a fossiliferous and geologically important geological Group of the Karoo Supergroup in South Africa. The thickest outcrops, reaching not more than , occur just east of Sutherland through to Beaufort West in the south and Victoria West in the north. Exposures are also found west of Colesberg and south of Graaff-Reinet. The Pristerognathus Assemblage Zone is the third biozone of the Beaufort Group.
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Blackwell Publishing The increasing knowledge of Labyrinthodonts from Romer's gap has led to the challenging of the hypothesis that pentadactyly, as displayed by most modern tetrapods, is plesiomorphic. The number of digits was once thought to have been reduced in amphibians and reptiles independently, but more recent studies suggest that a single reduction occurred, along the tetrapod stem, in the Late Devonian or Early Carboniferous. However, even the early Ichthyostegalians like Acanthostega and Ichthyostega appear to have had the forward ossified bony toes combined in a single stout digit, making them effectively five-toed.
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Skin of a sand lizard, showing squamate reptiles iconic Scales A white-headed dwarf gecko with shed tail Reptiles are tetrapod animals in the class Reptilia, comprising today's turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara, and their extinct relatives. The study of these traditional reptile orders, historically combined with that of modern amphibians, is called herpetology. List of reptiles lists the vertebrate class of reptiles by family, spanning two subclasses. 'Reptile' here is taken in its traditional (paraphyletic) sense, and thus birds are not included (although birds are considered reptiles in the cladistic sense).
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After the second duplication, the channel was left with two sets of similar domains. The resulting four-domain channel is thought to have been permeable primarily for calcium, and to have achieved sodium selectivity a number of times independently. After divergence from the invertebrates, the vertebrate lineage underwent two whole-genome duplications (WGDs), yielding a set of four sodium channel gene prologues in the ancestral vertebrate, all of which were retained. After the tetrapod/teleost split, the teleosts likely underwent a third WGD leading to the eight sodium channel prologues expressed in many modern fishes.
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She found that the Hangenberg event was immensely important for modern biodiversity and a bottleneck in the evolutionary history of vertebrates. During her PhD she studied the fossils of fish that diversified around the time of an extinction event, finding the head features diversified before body shapes. The work was covered in The New York Times, The Washington Post and Motherboard. After completing her PhD, Sallan joined the Michigan Society of Fellows at the University of Michigan She studied the early evolution of ray- finned fishes, including an early form with a tetrapod-like spine.
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However, fossils of Eunotosaurus show that the pelvis is in the normal tetrapod position and is placed over the ribs rather than within them, as in modern turtles. Many fossils have been found showing a semi-rigid, turtle-like rib cage, one which presumably necessitated a tortoise-like fashion of walking. Eunotosaurus was considered the ancestor of turtles up until the late 1940s. In his 1956 book Osteology of the Reptiles, American paleontologist Alfred Sherwood Romer claimed that Eunotosaurus could not be included within Chelonia based on the available evidence.
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This trait is possibly associated with early tetrapod evolution, which probably also appears on other members of this family and can act as a link to anuran tympanum evolution. The narrow head and elongated snout of Stanocephalosaurus suggests that stress levels during biting are slightly higher than temnospondyls with a wider and shorter skull. Its skull also has an elongated preorbital region compared to other mastodonsaurids. The vertebrae of Stanocephalosaurus are rhachitomous, with a neural arch and a bipartite centrum that is divided into a large, unpaired wedge-shaped intercentrum and smaller paired pleurocentra.
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Tetrapod groups which do possess an intertemporal typically have it contact the parietal bone along its inner edge, the postfrontal and postorbital bones along its front and/or outer edge, and the supratemporal bone along its rear edge. Rarely, the intertemporal may also contact the squamosal bone at a point between its contact with the postorbital and supratemporal. When the intertemporal bone is lost, either the postfrontal and supratemporal lengthen to contact each other (or the tabular bone in case the supratemporal is also lost), or the parietal widens to contact the postorbital.
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In the mid-19th century, John Phillips suggested three great systems: Palaeozoic, Mesozoic and Caenozoic. Writing after Sepkoski, Brenchley and Harper suggested that there were two early evolutionary faunas before the three of Sepkoski: Ediacaran and Tomottian. They also point out similarities with four "evolutionary terrestrial plant floras": Early Vascular, Pteridophytes, Gymnospores, Angiospores; and three "evolutionary terrestrial tetrapod faunas": "Megadynasty I (Carboniferous- early Permian)" "primitive amphibians and reptiles, most notably ... Dimetrodon", "Megadynasty II (early Permian-mid-Triassic)" "mammal-like therapsids", and "Megadynasty III (late Triassic-Cretaceous)" "included the age of the dinosaurs".
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Archipterygium (or ancient fin) is the concept of a primitive limb from which the limbs of tetrapod animals evolved. The idea was proposed by Karl Gegenbaur in 1878, sometimes termed the gill septum hypothesis and it consisted of a series of rays, one ray large with the remaining small ones attached to the sides of the large one. Gegenbaur based this idea on the fin of Ceratodus and its similarity to the gill-region in Elasmobranchs. He suggested that the pentadactyl limb of modern tetrapods was derived from one side of the archipterygium.
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Sigournea is a genus of stem tetrapod from the Early Carboniferous. The genus contains only one species, the type species Sigournea multidentata, which was named in 2006 by paleontologists John R. Bolt and R. Eric Lombard on the basis of a single lower jaw from Iowa. The jaw came from a fissure-fill deposit of the St. Louis Limestone that was exposed in a quarry near the town of Sigourney and dates to the Viséan stage, making it approximately 335 million years old. Bolt and Lombard named the genus after Sigourney.
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Balanerpeton woodi was discovered by Stanley Wood and is the earliest and most common tetrapod in the East Kirkton Limestone of the East Kirkton Quarry assemblage of terrestrial amphibians in Scotland. Characteristics of Balanerpeton woodi include the presence of large external nares, large interpterygoid vacuities (holes in the back of the palate), and an ear with a tympanic membrane and rod-like stapes. Numerous studies and research regarding ontogeny in non extant taxa have been oriented around this taxon. The morphology of the stapes suggests that the animal was capable of hearing high-frequency sound.
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Eucritta may have been a close relative of baphetids like Loxomma Eucritta was already recognized as a unique animal in its original 1998 description. A phylogenetic analysis provided in the description often found it close to baphetids, but groups at and around the base of crown-Tetrapoda were not stable in their position. The most parsimonious family tree tentatively placed Eucritta and baphetids closer to "anthracosaurs" than to temnospondyls. The more comprehensive 2001 description added the reptile-like tetrapod Gephyrostegus to the 1998 paper's phylogenetic analysis, and made several more edits and corrections.
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In response, Eucritta and the baphetids shifted their position, and a connection to temnospondyls became equally parsimonious. Clack commented that most of the connections between Eucritta, baphetids, and "anthracosaurs" were "plesiomorphies, ambiguous, or reversals". Ruta, Coates, and Quicke (2003)'s analysis of the tetrapod family tree placed Eucritta alone at the base of Temnospondyli. However, they also admitted that it would not be unlikely for it to have a variety of other positions scattered around the base of crown- Tetrapoda (the group encompassing the ancestors of all modern tetrapods, typically including temnospondyls and reptiliomorphs).
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The most important group to be affected by this extinction event were the reef-builders of the great Devonian reef systems. Amongst the severely affected marine groups were the brachiopods, trilobites, ammonites, conodonts, and acritarchs, as well as jawless fish, and all placoderms. Land plants as well as freshwater species, such as our tetrapod ancestors, were relatively unaffected by the Late Devonian extinction event (there is a counterargument that the Devonian extinctions nearly wiped out the tetrapods). The reasons for the Late Devonian extinctions are still unknown, and all explanations remain speculative.
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The museum holds extensive, representative samples of nearly all species - and most subspecies - of British Columbia's terrestrial vertebrates and marine mammals. The collection includes older specimens dating back to 1849, as well as rare specimens such as the red panda, the endangered Vancouver Island marmot, and even extinct species such as the passenger pigeon. Over 39,000 items from the Cowan Tetrapod Collection have been indexed in Vertnet, a "collaborative project funded by the National Science Foundation that aims to make biodiversity data free and openly accessible on the web from publishers worldwide".
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Digital restoration Panderichthys is a 90–130 cm long fish with a large tetrapod-like head that's flattened, narrow at the snout and wide in the back. The intracranial joint, which is characteristic of most lobe-fin fishes, has been lost from the external elements of the skull, but is still present in the braincase. The patterns of external bones in the skull roof and cheeks are more similar to those of early tetrapods than those of other lobe-fins. The transitional qualities of Panderichthys are also evident in the rest of the body.
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Euscolosuchus is an extinct genus of suchian closely related to crocodylomorphs. Fossils have been found from the Tomahawk Creek Member of the Turkey Branch Formation (part of the Newark Supergroup) outcropping in east- central Virginia. The locality from which the material was found dates back to the early Carnian stage of the Late Triassic, based on palynological studies. These strata are known for the abundance of fossil material belonging to tetrapod vertebrates in relation to other sites of the Newark Supergroup in the Richmond Basin that generally lack such material.
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Salamanders split off from the other amphibians during the mid- to late Permian, and initially were similar to modern members of the Cryptobranchoidea. Their resemblance to lizards is the result of symplesiomorphy, their common retention of the primitive tetrapod body plan, but they are no more closely related to lizards than they are to mammals. Their nearest relatives are the frogs and toads, within Batrachia. The earliest known salamander fossils have been found in geological deposits in China and Kazakhstan, dated to the middle Jurassic period around 164 million years ago.
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In most tetrapod species, there are two paired thyroid glands – that is, the right and left lobes are not joined together. However, there is only ever a single thyroid gland in most mammals, and the shape found in humans is common to many other species. In larval lampreys, the thyroid originates as an exocrine gland, secreting its hormones into the gut, and associated with the larva's filter-feeding apparatus. In the adult lamprey, the gland separates from the gut, and becomes endocrine, but this path of development may reflect the evolutionary origin of the thyroid.
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Reptiles are tetrapod animals in the class Reptilia, comprising today's turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara, and their extinct relatives. The study of these traditional reptile orders, historically combined with that of modern amphibians, is called herpetology. Because some reptiles are more closely related to birds than they are to other reptiles (e.g., crocodiles are more closely related to birds than they are to lizards), the traditional groups of "reptiles" listed above do not together constitute a monophyletic grouping or clade (consisting of all descendants of a common ancestor).
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Pubo-ischiadic plates, primitive forms of the pubis and ischium of later tetrapods, are present, but it is unclear whether they were fused into a strong pelvic girdle. A small projection of bone is present on the acetabulum, a depression in the pelvis that attaches with the end of the femur. This projection is also seen in the Late Devonian tetrapod Ichthyostega. The femur of Antlerpeton is much more robust than that of Ichthyostega, and has prominent ridges like the fourth trochanter that are attachment points for well-developed leg muscles.
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He went on to teach at both Columbia and Harvard. In his later life, Jenkins served at Harvard as a professor of biology, the Alexander Agassiz Professor of Zoology and curator of vertebrate paleontology at the Museum of Comparative Zoology. Jenkins made numerous expeditions to the Arctic, including a dozen expeditions to the Triassic of Jameson Land in Greenland, and to other sites from East Africa to Wyoming. He is credited as having helped explain the fish-to-tetrapod evolutionary transition as he helped discover the 375 million year old Tiktaalik roseae.
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Megamolgophis is an extinct genus of eel-like tetrapod, possibly belonging to the group Lysorophia. Fossils from this genus have been found in the Allegheny mountains of the eastern United States. The genus is endemic to geological formations of this area, such as the Greene and Washington formations of the Early Permian Dunkard Group, as well as the Pennsylvanian (Late Carboniferous) Conemaugh Group. If correctly assigned to Lysorophia, members of Megamolgophis would not only be the largest known lysorophians, but also some of the largest lepospondyls in general.
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Life restoration of G. gigantea, a species found in North America Gastornis fossils are known from across western Europe, the western United States, and central China. The earliest (Paleocene) fossils all come from Europe, and it is likely that the genus originated there. Europe in this epoch was an island continent, and Gastornis was the largest terrestrial tetrapod of the landmass. This offers parallels with the malagasy elephant birds, herbivorous birds that were similarly the largest land animals in the isolated landmass of Madagascar, in spite of otherwise mammalian megafauna.
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Insects must carefully coordinate their six legs during walking to produce gaits that allow for efficient navigation of their environment. Interleg coordination patterns have been studied in a variety of insects, including locusts (Schistocerca gregaria), cockroaches (Periplaneta americana), stick insects (Carausius morosus), and fruit flies (Drosophila melanogaster). Different walking gaits have been observed to exist on a speed dependent continuum of phase relationships. Even though their walking gaits are not discrete, they can often be broadly categorized as either a metachronal wave gait, tetrapod gait, or tripod gait.
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The true ribs are small projections, with small, hooked bones, called uncinate processes, found on the rear of each rib. This feature is also present in birds. The tuatara is the only living tetrapod with well-developed gastralia and uncinate processes. In the early tetrapods, the gastralia and ribs with uncinate processes, together with bony elements such as bony plates in the skin (osteoderms) and clavicles (collar bone), would have formed a sort of exoskeleton around the body, protecting the belly and helping to hold in the guts and inner organs.
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Temnospondyls and other early tetrapods have rounded otic notches in the back of the skull that project into the cheek region. In life, the otic notch would have been covered by a membrane called the tympanum, which is seen as a disk-like area in living frogs. The tympanum is involved in hearing, and is similar to the ear drum of more advanced tetrapods. It was traditionally thought that the tympanum developed very early in tetrapod evolution as a hearing organ and progressed to form the eardrum of amniotes.
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Chapter on Crassigyrinus from Gaining ground: the origin and evolution of tetrapods, by Jennifer A. Clack, Indiana University Press 2002, from Google Books It was traditionally placed within the group Labyrinthodontia along with many other early tetrapods. Some paleontologists have even considered it as the most basal Crown group tetrapod, while others hesitate to even place it within the Tetrapoda superclass. Crassigyrinus had unusually large jaws, enabling it to eat other animals it could catch and swallow. It had two rows of sharp teeth in its jaws, the second row having a pair of fangs.
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The waterfall climbing cave fish (Cryptotora thamicola), also known as the cave angel fish, is a species of troglobitic hillstream loach endemic to Thailand. It reaches a length of SL. This fish is known for its fins, which can grapple onto terrain, and its ability to climb.Brooke E. Flammang, Apinun Suvarnaraksha, Julie Markiewicz & Daphne Soares, Tetrapod-like pelvic girdle in a walking cavefish, Scientific Reports 6 (2016) This fish is the only known member of its genus.Kottelat, M. (2012): Conspectus cobitidum: an inventory of the loaches of the world (Teleostei: Cypriniformes: Cobitoidei).
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Spathicephalus was not included in a modern phylogenetic analysis of early tetrapod relationships until the 2000s. In 2009, paleontologists Angela Milner, Andrew Milner, and Stig Walsh incorporated the anatomical characteristics of S. mirus into an analysis of baphetoid interrelationships. The analysis placed Spathicephalus just outside Baphetidae as the sister taxon of the group, a result which they used to justify its placement in a distinct family, Spathicephalidae. The analysis also found Eucritta melanolimnetes, an older species from the Viséan stage of Scotland, to be the most basal member of Baphetoidea.
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Lochalsh was very similar to Kyleakin which had been the first group ferry to be built outside Scotland, the first with drive-through capability and the first to be equipped with Voith-Schneider propulsion. She was built with large hydraulic ramps at both ends of a vehicle deck, strengthened to carry vehicles up to 32 tons. A narrow lounge along one side, with an deck open above provided passengers accommodation. While Kyleakin had only one plain gantry mast on her wheelhouse, Lochalsh had an elaborate tetrapod mast at each end.
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A third, evolutionarily younger, function of the basilar membrane is strongly developed in the cochlea of most mammalian species and weakly developed in some bird species: Fritzsch B: The water-to-land transition: Evolution of the tetrapod basilar papilla; middle ear, and auditory nuclei. In: the dispersion of incoming sound waves to separate frequencies spatially. In brief, the membrane is tapered and it is stiffer at one end than at the other. Furthermore, sound waves travelling to the "floppier" end of the basilar membrane have to travel through a longer fluid column than sound waves travelling to the nearer, stiffer end.
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However, most tetrapod species today are amniotes, most of those are terrestrial tetrapods whose branch evolved from earlier tetrapods about 340 million years ago (crown amniotes evolved 318 million years ago). The key innovation in amniotes over amphibians is laying of eggs on land or having further evolved to retain the fertilized egg(s) within the mother. Amniote tetrapods began to dominate and drove most amphibian tetrapods to extinction. One group of amniotes diverged into the reptiles, which includes lepidosaurs, dinosaurs (which includes birds), crocodilians, turtles, and extinct relatives; while another group of amniotes diverged into the mammals and their extinct relatives.
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Tiktaalik also had a pattern of bones in the skull roof (upper half of the skull) that is similar to the end-Devonian tetrapod Ichthyostega. The two also shared a semi-rigid ribcage of overlapping ribs, which may have substituted for a rigid spine. In conjunction with robust forelimbs and shoulder girdle, both Tiktaalik and Ichthyostega may have had the ability to locomote on land in the manner of a seal, with the forward portion of the torso elevated, the hind part dragging behind. Finally, Tiktaalik fin bones are somewhat similar to the limb bones of tetrapods.
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In typical early tetrapod posture, the upper arm and upper leg extended nearly straight horizontal from its body, and 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 touched the ground. Most of the animal's strength was used to just lift its body off the ground for walking, which was probably slow and difficult. With this sort of posture, it could only make short broad strides.
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In the static system, the jaw muscles are arranged in such a way that the jaws have maximum force when shut or nearly shut. In the kinetic inertial system, maximum force is applied when the jaws are wide open, resulting in the jaws snapping shut with great velocity and momentum. Although the kinetic inertial system is occasionally found in fish, it requires special adaptations (such as very narrow jaws) to deal with the high viscosity and density of water, which would otherwise impede rapid jaw closure. The tetrapod tongue is built from muscles that once controlled gill openings.
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Because species of aetosaurs typically have restricted fossil ranges and are abundant in the strata they are found in, they are useful in biochronology. Osteoderms are the most common remains associated with aetosaurs, so a single identifiable scute can accurately date the layer it is found in. One aetosaur, Typothorax coccinarum, has been used to define the Revueltian land vertebrate faunachron. A land vertebrate faunachron (LVF) is a time interval that is defined by the first appearance datum (FAD), or first occurrence, of a tetrapod index fossil and is commonly used to date Late Triassic and Early Jurassic terrestrial strata.
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A Darwin fish with stylized legs resembling an Ichthyostega, a four limb fish The Darwin fish is a fish symbol with "evolved" legs and feet attached, and often with the word "Darwin" inside (like the ΙΧΘΥΣ or Jesus found in some Christian versions). It symbolizes the scientific theories of evolution, for which Charles Darwin laid a foundation, in contrast with creationism, which is a hallmark of American Christianity. The Darwin fish bears a stylized resemblance to Tiktaalik or Ichthyostega, which are major examples of a transitional fossil of the first tetrapod that moved from sea to dry land during the Late Devonian period.
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Arthropods evolved herbivory in four phases, changing their approach to it in response to changing plant communities. Tetrapod herbivores made their first appearance in the fossil record of their jaws near the Permio-Carboniferous boundary, approximately 300 million years ago. The earliest evidence of their herbivory has been attributed to dental occlusion, the process in which teeth from the upper jaw come in contact with teeth in the lower jaw is present. The evolution of dental occlusion led to a drastic increase in plant food processing and provides evidence about feeding strategies based on tooth wear patterns.
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A pubo-ischiadic symphysis is also observed, uniting the two pelvic halves. In contrast, Protopterus annectens (a member of lungfish, thought to be a sister group to tetrapods) has a small, anatomically simpler pelvis, a derived limb endoskeleton and a lack of digits. Yet, it shares the ability to lift itself using a solid surface as a base with its pelvic region with Acanthostega and is also observed to move with tetrapod-like locomotion in an aquatic environment. This illustrates that a fundamental innovation in tetrapods is also found in a lower, sister taxon, in which members lack a sacrum.
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Researchers conducted a study targeting the Hox-9 to Hox-13 genes in different species of frogs and other amphibians. Similar to an ancient tetrapod group with assorted limb types, it is important to note that amphibians are required for the understanding of the origin and diversification of limbs in different land vertebrates. A PCR (Polymerase Chain Reaction) study was conducted in two species of each amphibian order to identify Hox-9 to Hox-13. Fifteen distinct posterior Hox genes and one retro-pseudogene were identified, and the former confirm the existence of four Hox clusters in each amphibian order.
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Skull of Sclerocephalus, showing the otic notches Otic notches are invaginations in the posterior margin of the skull roof, one behind each orbit. Otic notches are one of the features lost in the evolution of amniotes from their tetrapod ancestors. The notches have been interpreted as part of an auditory structure and are often reconstructed as holding a tympanum similar to those seen in modern anurans. Analysis of the columella (the stapes in amphibians and reptiles) of labyrinthodonts however indicates that it did not function in transmitting low-energy vibrations, thus rendering these animals effectively deaf to airborne sound.
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Marjanovic & Laurin (2019) utilized Saharastega as part of their many reanalyses of Ruta & Coates (2007)'s tetrapod study. The original 2007 study did not include Saharastega, so it was added along with Nigerpeton and many other taxa in some of the reanalyses. Although Marjanovic & Laurin (2019) did not place Saharastega close to cochleosaurids or other edopoids (at least in their parsimony analyses), the study consistently placed it as the sister taxon to Nigerpeton. The clade containing these two unusual temnospondyls had an inconsistent placement, with a connection to Eryops, stereospondylomorphs, or the very base of Temnospondyli each considered equally likely.
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The front margin of each osteoderm has a pair of "anterior wings" that slip into a notch in the posterior margin of the osteoderm in front of it. Diagram showing different types of tetrapod vertebrae, including the vertebra of the chroniosuchian Bystrowiella schumanni. Chroniosuchians are distinguished from other early reptiliomorphs by the lack of intertemporal bones in the skull, as well as the presence of holes in front of the eye sockets called antorbital fenestrae. Like many early tetrapods, chroniosuchians have vertebrae that are divided into three parts: a pleurocentrum and an intercentrum on the bottom, and a neural arch on top.
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Barrett first went to the Antarctica with the University of Wisconsin in 1962, but it was during his PhD with the Institute of Polar Studies at Ohio State University in 1966 and 1968 that Barrett discovered the early Triassic period tetrapod remains. After finishing his PhD, he took up a postdoctoral fellowship at Victoria University of Wellington to run an Antarctic expedition. Recent research has been core sampling in the Antarctic to determine historical conditions. He is currently professor in the Antarctic Research Centre at Victoria University of Wellington and was director of the ARC from its founding in 1972 until 2007.
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Tetrapod Zoology @ScienceBlogs Sinosauropteryx fossil, the first fossil of a definitively non-avialan dinosaur with feathers After a century of hypotheses without conclusive evidence, well-preserved fossils of feathered dinosaurs were discovered during the 1990s, and more continue to be found. The fossils were preserved in a Lagerstätte—a sedimentary deposit exhibiting remarkable richness and completeness in its fossils—in Liaoning, China. The area had repeatedly been smothered in volcanic ash produced by eruptions in Inner Mongolia 124 million years ago, during the Early Cretaceous epoch. The fine-grained ash preserved the living organisms that it buried in fine detail.
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Vivian de Buffrénil is a French histologist and paleobiologist who has been working at the Muséum National d'Histoire Naturelle in Paris since 1982. His doctorate (1980) and his doctorat d'état (1990), a diploma now replaced by the habilitation, were supervised by Armand de Ricqlès. His main fields of interest include basic histological descriptions, growth dynamics as recorded in bone growth marks, and adaptation (both histological and microanatomical) of the tetrapod skeleton to a secondarily aquatic lifestyle. He is also interested in life history and population dynamics of exploited or threatened reptile taxa, especially among Varanidae and Crocodilia.
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In contrast, the tetrapods have only one pair of nares externally but also sport a pair of internal nares, called choanae, allowing them to draw air through the nose. Lungfish are also sarcopterygians with internal nostrils, but these are sufficiently different from tetrapod choanae that they have long been recognized as an independent development. The evolution of the tetrapods' internal nares was hotly debated in the 20th century. The internal nares could be one set of the external ones (usually presumed to be the posterior pair) that have migrated into the mouth, or the internal pair could be a newly evolved structure.
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Pelvic bone fossils from Tiktaalik shows, if representative for early tetrapods in general, that hind appendages and pelvic-propelled locomotion originated in water before terrestrial adaptations. Another indication that feet and other tetrapod traits evolved while the animals were still aquatic is how they were feeding. They did not have the modifications of the skull and jaw that allowed them to swallow prey on land. Prey could be caught in the shallows, at the water's edge or on land, but had to be eaten in water where hydrodynamic forces from the expansion of their buccal cavity would force the food into their esophagus.
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Restoration showing placement of a fractured right radius There is a fractured right radius of a particular specimen that shines light onto early tetrapod habitualization. A broken radius found among the Ossinodus remains in Australia suggests they must have spent a significant portion of their time on land. Through finite force analysis, the amount of force necessary to acquire the damage found on the bone is only possible from a fall of a certain height. It is unsure if Ossinodus were mainly aquatic or terrestrial, but it is safe to say that they spent time both in water and on land.
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D.M.S. Watson (1926) assigned two more complete specimens to the genus. One of these had already been named as the type specimen of the reptile-like tetrapod Gephyrostegus by Otto Jaekel in 1902, while the second specimen, DMSW B.65, was newly described. A later study, Brough & Brough (1967), restored the validity of Gephyrostegus and rebuked Watson's decision to add Jaekel's and his specimens to Diplovertebron. Richard Lydekker renamed Diplovertebron to Diplospondylus in 1889, based on the fact that the etymology of "Diplospondylus" was all Greek, while that of "Diplovertebron" was a hybrid of Greek and Latin.
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Panthera schaubi or Viretailurus schaubi was historically often regarded as a basal member of the genus Panthera. However, recent work"Pumas of South Africa, cheetahs of France, jaguars of England", Tetrapod Zoology has shown that Viretailurus should actually be included in the genus Puma as a junior synonym of Puma pardoides. Fossils of this leopard-sized animal are around 2 million years old and were found in France. However, their classification was difficult, due to the similarities between leopards and pumas, until teeth found at the Upper Pliocene Transcaucasian site of Kvabebi were found to be similar to those of pumas..
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Lobe- finned fishes, such as coelacanths and lungfish, were the most diverse group of bony fishes in the Devonian. Taxonomists who subscribe to the cladistic approach include the grouping Tetrapoda within the Sarcopterygii, and the tetrapods in turn include all species of four-limbed vertebrates. The fin- limbs of lobe-finned fishes such as the coelacanths show a strong similarity to the expected ancestral form of tetrapod limbs. The lobe-finned fish apparently followed two different lines of development and are accordingly separated into two subclasses, the Rhipidistia (including the lungfish, and the Tetrapodomorpha, which include the Tetrapoda) and the Actinistia (coelacanths).
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The Lystrosaurus Assemblage Zone is a tetrapod assemblage zone or biozone which correlates to the upper Adelaide and lower Tarkastad Subgroups of the Beaufort Group, a fossiliferous and geologically important geological Group of the Karoo Supergroup in South Africa. This biozone has outcrops in the south central Eastern Cape (Middelburg, Queenstown, Aliwal North, Nieu-Bethesda) and in the southern and northeastern Free State (Bethulie, Gariep Dam, Mthatha, Harrismith). The Lystrosaurus Assemblage Zone is one of eight biozones found in the Beaufort Group, and is considered to be Early Triassic in age.Keyser, A. W., & Smith, R. M. H. (1978).
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The Skellig Islands lie about 12 kilometres (7.5 statute miles or 6.4 nautical miles) off the west coast and are known for their monastic buildings and bird life. Kerry Geopark is a community initiative on the Iveragh Peninsula which aims to promote geotourism in this area of high geological importance. Some of the interest features are Kenmare Bay (a drowned river valley or ria), signs of past glaciation and volcanic activity and 400-million-year-old fossilised tetrapod tracks. Cloghanecarhan, a ringfort with ogham stone, is a National Monument; as is Leacanabuaile, a stone ringfort (cashel).
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At least nine genes in the Hox complex has been lost in Fugu when compared to present mammalian complexes. This data demonstrates that gene loss of prototypical Hox clusters is a defining feature in both tetrapod and fish evolution. "'Shocking' developments in chick embryology: electroporation and in ovo gene expression" (1999) This paper focuses on new approaches to the analysis of gene expression through the use of electroporation. This work focuses on the protocol for electroporation, how it can be applied to differing organisms, and the future experiments that could be conducted through the use of electroporation.
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The Beaty Biodiversity Museum is a natural history museum in Vancouver, British Columbia, Canada, located on the campus of the University of British Columbia. Its of collections and exhibit space were first opened to the public on October 16, 2010; since then it has received over 35,000 visitors per year. Its collections include over two million specimens collected between the 1910s and the present, comprising the Cowan Tetrapod Collection, the Marine Invertebrate Collection, the Fossil Collection, the Herbarium, the Spencer Entomological Collection, and the Fish Collection. The collections focus in particular on the species of British Columbia, Yukon, and the Pacific Coast.
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After obtaining his Ph.D., he held a two-year postdoctoral fellowship at Redpath Museum at McGill University in Montréal, and then at the Natural History Museum in London. During this time he studied tetrapod remains from the Pennsylvanian lycopod “tree stumps” at Joggins, Nova Scotia (a variety of temnospondyls, microsaurs, and basal amniotes). Most of this material was collected and first studied by Sir William Dawson, the first Principal of McGill University, in the nineteenth century. Returning from London, in 1964 Carroll joined the permanent staff of McGill University as curator of vertebrate paleontology at the Redpath Museum.
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Dinosauroids Revisited Darren Naish: Tetrapod Zoology, April 23, 2011. Russell's thought experiment has been met with criticism from other paleontologists since the 1980s, many of whom point out that his Dinosauroid is overly anthropomorphic. Gregory S. Paul (1988) and Thomas R. Holtz, Jr., consider it "suspiciously human" (Paul, 1988) and Darren Naish has argued that a large-brained, highly intelligent troodontid would retain a more standard theropod body plan, with a horizontal posture and long tail, and would probably manipulate objects with the snout and feet in the manner of a bird, rather than with human-like "hands".
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Dermal bones of Umzantsia carry a distinctive ornament consisting of fine parallel ridges reminiscent of water ripples. This allows identification of a number of cranial bones and a cleithrum from one bedding plane which are probably derived from a single individual. The dermal ornament covers about 80% of the cleithrum of Umzantsia; this fishlike characteristic contrasts with the un-ornamented cleithra of most other Devonian tetrapods, suggesting a phylogenetic position between those tetrapods and their sister group, the Elpistostegalians. The only other tetrapod with dermal ornaments on the cleithrum is Parmastega though it covers far less of the cleithrum.
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Dinosauroids Revisited Darren Naish: Tetrapod Zoology, April 23, 2011. However, Russell's thought experiment has been met with criticism from other paleontologists since the 1980s, many of whom point out that his Dinosauroid is overly anthropomorphic. Gregory S. Paul (1988) and Thomas R. Holtz, Jr., consider it "suspiciously human" and Darren Naish has argued that a large-brained, highly intelligent troodontid would retain a more standard theropod body plan, with a horizontal posture and long tail, and would probably manipulate objects with the snout and feet in the manner of a bird, rather than with human-like "hands".
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Several living subgroups are recognized: Testudines (turtles and tortoises), 350 species; Rhynchocephalia (tuatara from New Zealand), 1 species; Squamata (lizards, snakes, and worm lizards), over 10,200 species; and Crocodilia (crocodiles, gharials, caimans, and alligators), 24 species. Reptiles are tetrapod vertebrates, creatures that either have four limbs or, like snakes, are descended from four-limbed ancestors. Unlike amphibians, reptiles do not have an aquatic larval stage. Most reptiles are oviparous, although several species of squamates are viviparous, as were some extinct aquatic clades – the fetus develops within the mother, using a (non-mammalian) placenta rather than contained in an eggshell.
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It had internal gills that were covered like those of fish. It also had lungs, but its ribs were too short to support its chest cavity out of water. It has been inferred that Acanthostega probably lived in shallow, weed- choked swamps, its legs apparently being adapted for these specific ecosystems (the animal was not adapted in any way for walking on land). Jennifer A. Clack interprets this as showing that Acanthostega was primarily an aquatic animal descended from fish that never left the sea, and that the specializations in the tetrapod lineage developed features which would later be useful for terrestrial life.
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The classification of Acherontiscus has gone through much revision in the past, as it shows a mixture of characteristics from various groups of non-amniote tetrapods (amphibians in the broad definition of the term). Traditionally, ancient amphibians have been classified into two groups: labyrinthodonts and lepospondyls. Labyrinthodonts can be characterized by their maze-like tooth enamel, the presence of multiple bones forming each vertebral segment, and a generally crocodile-like appearance. Modern analyses have concluded that the order "Labyrinthodontia" is composed of various groups of non-amniote stegocephalians scattered within and near the tetrapod family tree.
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Alveusdectes is an extinct genus of diadectid tetrapod (represented by the type species Alveusdectes fenestralis) from the Late Permian of China. Like other diadectids, it was a large-bodied terrestrial herbivore capable of eating tough fibrous plant material. It was described in 2015 on the basis of a single partial skull and lower jaw found in the Shangshihezi Formation near the city of Jiyuan in Henan. This skull was found in a layer of the Shangshihezi Formation that dates to about 256 million years ago and contains the remains of many other terrestrial tetrapods including pareiasaurs, chroniosuchians, and therapsids.
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In a metachronal wave gait, only one leg leaves contact with the ground at a time. This gait starts at one of the hind legs, then propagates forward to the mid and front legs on the same side before starting at the hind leg of the contralateral side . The wave gait is often used at slow walking speeds and is the most stable, since five legs are always in contact with the ground at a time. In a tetrapod gait, two legs swing at a time while the other four legs remain in contact with the ground.
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Owen used these fossils to counter the notion that reptiles evolved from a sequential progression from early amphibians (what he called "metamorphosed fishes"). In addition to Mastodonsaurus, some of the earliest named genera included Metopias and Rhombopholis in 1842, Zygosaurus in 1848, Trematosaurus in 1849, Baphetes and Dendrerpeton in 1853, Capitosaurus in 1858, and Dasyceps in 1859. Baphetes is now placed as an early tetrapod outside Temnospondyli, and Rhombopholis is now considered a prolacertiform reptile. Later in the 19th century, temnospondyls were classified as various members of Stegocephalia, a name coined by the American paleontologist Edward Drinker Cope in 1868.
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The enigmatic Carboniferous tetrapod species Doragnathus woodi may be related to Spathicephalus. In two papers published in 1993 and 1994, Russian paleontologist O. A. Lebedev proposed that Doragnathus was a junior synonym of Spathicephalus. Doragnathus woodi, named by Smithson in 1980 from the Dora Open Cast Mine in Fife, Scotland (the same mine where paleontologist Stanley P. Wood discovered remains of S. mirus), is known only from upper and lower jaw fragments. The jaws themselves closely resemble those of other Carboniferous tetrapods, but the numerous very small, closely packed, pointed, and inward (lingually) curving marginal teeth they hold are unique.
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Another stem tetrapod, Sigournea multidentata from the Early Carboniferous of the United States, may also be related to Spathicephalus. Named in 2006 from a Visean-aged fissure fill deposit in Iowa, Sigournea is slightly older than Spathicephalus. It resembles both Spathicephalus and Doragnathus in having numerous small, closely packed teeth. Sigournea differs from Spathicephalus and resembles Doragnathus in having pointed rather than chizel-shaped marginal teeth and a second row of teeth in the lower jaws, and differs from both taxa in having a hole on the inner surface of the lower jaw called the exomeckelian fenestra.
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The Joggins Formation is famous for these tree trunks, as while they are valuable in their own right they also protected the carcasses of many animals which fossilized as well. It is unknown how creatures like Hylerpeton or Dendropupa came to be trapped in the trunks, but it has been suggested they were either using the trees as dens, or they fell into the hollow trunks as the trees were rotting and were buried when sediment collapsed into the interior. One trunk recovered from the Joggins Formation contained thirteen separate vertebrate specimens. A total of eleven tetrapod species have been discovered within fossil tree trunks at Joggins.
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Hyphalosaurus is the most abundant tetrapod (four-limbed vertebrate) in the Yixian Formation, and probably played an important role in the aquatic food chain. Its long and highly flexible neck and small, flattened skull indicates that it captured small prey animals like fish or arthropods using a sideways-strike, similar to modern aquatic predators with flattened skulls. Unlike other choristoderans, Hyphalosaurus was likely an active predator, rather than one that used a "sit and wait" ambush strategy. Its fossils are often found preserved alongside the small fish Lycoptera, which may have been a prey item, and at least one specimen preserved fish ribs as stomach contents.
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Swim traces referrable to lysorophians have been found at the Robledo mountains of New Mexico, an area famous for its Permian tetrapod trackways. Designated as the ichnogenus Serpentichnus, these marks occur as a series of L-shaped grooves, which are divided into two shafts: a long, diagonal shaft preceded by a shorter, forward-pointing shaft offset at a 150% angle. What seem to be tiny foot impressions occur on either side of the series of groves. When originally described in 2003, Serpentichnus tracks were argued to have been formed by a long-bodied animal with small limbs, moving in a "sidewinding" motion along a riverbed.
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The layer of the Altenglan Formation in which Altenglanerpeton was found is thought to have been deposited in a lake environment, specifically that of Hauptkalk Lake, a large, shallow body of water that covered much of the Saar–Nahe Basin at the Carboniferous-Permian transition. Sedimentation rates in the lake were low, meaning that few fossils were preserved. Besides the Altenglanerpeton skeleton, only three tetrapod fossils are known from Hauptkalk Lake deposits: two specimens of the temnospondyl Apateon pedestris and a skull of the temnospondyl Sclerocephalus bavaricus. The microsaur Batropetes is also known from the Saar-Nahe Basin, but it comes from the younger Odernheim Subformation.
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SOX1 is a gene that encodes a transcription factor with a HMG-box (high mobility group) DNA-binding domain and functions primarily in neurogenesis. SOX1, SOX2 and SOX3, members of the SOX gene family (specifically the SOXB1 group), contain transcription factors related to SRY, the testis-determining factor. SOX1 exerts its importance in its role in development of the central nervous system (neurogenesis) and in particular the development of the eye, where it is functionally redundant with SOX3 and to a lesser degree SOX2, and maintenance of neural progenitor cell identity. SOX1 expression is restricted to the neuroectoderm by proliferating progenitor cells in the tetrapod embryo.
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The pectoral fins developed into forelegs (arms in the case of humans) and the pelvic fins developed into hind legs.Hall, Brian K (2007) Fins into Limbs: Evolution, Development, and Transformation University of Chicago Press. . Much of the genetic machinery that builds a walking limb in a tetrapod is already present in the swimming fin of a fish.Shubin, Neil (2009) Your inner fish: A journey into the 3.5 billion year history of the human body Vintage Books. . UCTV interviewClack, Jennifer A (2012) "From fins to feet" Chapter 6, pages 187–260, in: Gaining Ground, Second Edition: The Origin and Evolution of Tetrapods, Indiana University Press. .
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According to Scott D. Sampson, if ceratopsids were to have sexual dimorphism modern ecological analogues suggest it would be in their mating signals like horns and frills. No convincing evidence for sexual dimorphism in body size or mating signals is known in ceratopsids, although was present in the more primitive ceratopsian Protoceratops andrewsi whose sexes were distinguishable based on frill and nasal prominence size. This is consistent with other known tetrapod groups where midsized animals tended to exhibit markedly more sexual dimorphism than larger ones. However, if there were sexually dimorphic traits they may have been soft tissue variations like colorations or dewlaps that would not have been preserved as fossils.
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The development of the pelvic region was crucial for the adaptation from water to land, yet some features of tetrapod locomotion are thought to have arose before the origin of digited limbs or the transition from water to land. The fossil record of early tetrapods shows evidence of distinct pelvic development occurring in osteolepiforms, further supporting osteolepiform ancestry of terrestrial tetrapods. Acanthostega has a large pelvis, with the iliac region articulating with the axial skeleton and a broad ischial plate. It has a sacrum; a fundamental skeletal feature that allows the organism to transfer force produced in its hindlimbs to its axial skeleton, and move in a terrestrial environment.
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Gruber and Sparks (2015) have observed the first fluorescence in a marine tetrapod (four- limbed vertebrates). Sea turtles are the first biofluorescent reptile found in the wild. According to Gruber and Sparks (2015), fluorescence is observed in an increasing number of marine creatures (cnidarians, ctenophores, annelids, arthropods, and chordates) and is now also considered to be widespread in cartilaginous and ray-finned fishes. The two marine biologists accidentally made the observation in the Solomon Islands on a hawksbill sea turtle, one of the rarest and most endangered sea turtle species in the ocean, during a night dive aimed to film the biofluorescence emitted by small sharks and coral reefs.
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In 2012, Wuqiu, along with Daren Township in Taitung County, was proposed by the Ministry of Economic Affairs as the candidate of the new disposal site of nuclear waste after the Lanyu storage site in Orchid Island, Taitung County. This proposal however received heavy objection from the local Wuqiu residents. On July 23, 2017, after a period of sixty years in which the lighthouse remained disused, the Wuqiu Lighthouse resumed service. On August 24, 2017, Chen Fu-Hai, then-magistrate of Kinmen County, visited the Wuqiu Township Office. On the night of August 2, 2019, a cargo ship in port at Wuqiu struck a tetrapod in choppy waves.
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Two years later, Mun acknowledged that it had become physically impossible to continue to block the expansion site--which was then guarded by South Korean soldiers and concertina wire--but maintained his belief that the activists' cause was "just" and that the U.S. military would someday have to leave South Korea. Mun moved to Gangjeong Village, Seogwipo City, Jeju Province, in 2011 to live in solidarity with protesters against the construction of an ROK Naval base, which in his opinion will also be a U.S. Naval base in some way. In April 2012, he fell from a concrete tetrapod during a protest, fracturing several vertebrae.
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A late 19th century illustration of Mastodonsaurus and Hyperodapedon in their environment Hyperodapedon are commonly found in aeolian sand in Elgin, India, Brazil, and Argentina. They are a widely distributed tetrapod during the Upper Triassic and are present in locations where phytosaurs are absent. Hyperodapedon localities are found in the Popo Agie Formation in Wyoming and the Wolfville Formation in Nova Scotia that date to the Otischalkian. They are also found in Scotland in the Lossiemouth Sandstone dating to the Adamanian, Maleri Formation in India, Pebbly Arkose Formation in Zimbabwe, Isalo II Beds in Madagascar, Ischigualasto Formation in Argentina, and Santa Maria Formation in Brazil that vary between Otischalkian and Adamanian.
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The tracks, some of which show digits, date to about 395 million years ago—18 million years earlier than the oldest known tetrapod body fossils. Additionally, the tracks show that the animal was capable of thrusting its arms and legs forward, a type of motion that would have been impossible in tetrapodomorph fish like Tiktaalik. The animal that produced the tracks is estimated to have been up to long with footpads up to wide, although most tracks are only wide. The new finds suggest that the first tetrapods may have lived as opportunists on the tidal flats, feeding on marine animals that were washed up or stranded by the tide.
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The recovered remains were deemed to belong in the same group O. pueri due to common ornamentation on the dermal cranial bones. The specimens were found at the Drummond Basin of Queensland, Australia, in the Middle Paddock site of the Duckabrook Formation. Estimated to be about 333 million years old, the Middle Paddock site is representative of “a shallow fluviatile or lacustrine environment,” which is a large body of water with sedimentary deposits made of slits, clays, and carbonates. The tetrapodal remains found here date back to Late Visean (early Carboniferous), towards the end of Romer’s Gap - a gap in the tetrapod fossil record.
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The type species, A. longidentatum, was initially described by John William Dawson on the basis of RM 2.1129, a left mandible. This fossil hailed from the Joggins fossil cliffs, a site in Nova Scotia famous for fossil deposits dated to the Bashkirian, the first stage of the Pennsylvanian subperiod of the Carboniferous period. A. longidentatum was originally named Hylerpeton longidentatum, as Dawson considered it a new species of the microsaur Hylerpeton, distinct from Hylerpeton dawsoni (the type species of Hylerpeton). Steen (1934) and Carroll (1966) questioned the microsaurian placement of H. longidentatum, but withheld judgment on its taxonomic status, although Carroll (1966) noted similarities to non-tetrapod sarcopterygians.
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In the Purple Clay Formation, Counillonia is currently only known to have co-existed with the basal kannemeyeriiform dicynodont Repelinosaurus and the semi-aquatic chroniosuchian tetrapod Laosuchus. The only direct evidence of plants in the formation are preserved root traces in palaeosols, but a locality underlying the Purple Claystone Formation and above late Changhsingian (Late Permian) deposits preserves a rich and diverse palaeoflora. The sediments preserved indicate that the Purple Clay Formation was deposited in a braided river environment that gradually transitioned to an alluvial plain with ponds. The region was volcanically active, as evidenced by the volcaniclastic rocks mixed in with the sediments of the formation.
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It could generate a bite force of around 3,341 newtons. This interpretation was questioned by François Therrien and colleagues (2005), who found that the biting force of Carnotaurus was twice that of the American alligator, which may have the strongest bite of any living tetrapod. These researchers also noted analogies with modern Komodo dragons: the flexural strength of the lower jaw decreases towards the tip linearly, indicating that the jaws were not suited for high precision catching of small prey but for delivering slashing wounds to weaken big prey. As a consequence, according to this study, Carnotaurus must have mainly preyed upon large animals, possibly by ambush.
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In the Purple Clay Formation, Repelinosaurus is currently only known to have co-existed with the "Dicynodon"-grade dicynodont Counillonia and the semi-aquatic chroniosuchian tetrapod Laosuchus. The only direct evidence of plants in the formation are preserved root traces in palaeosols, but a locality underlying the Purple Claystone Formation and above late Changhsingian (Late Permian) deposits preserves a rich and diverse palaeoflora. The sediments preserved indicate that the Purple Clay Formation was deposited in a braided river environment that gradually transitioned to an alluvial plain with ponds. The region was volcanically active, as evidenced by the volcaniclastic rocks mixed in with the sediments of the formation.
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The Tapinocephalus Assemblage Zone is a tetrapod assemblage zone or biozone which correlates to the middle Abrahamskraal Formation, Adelaide Subgroup of the Beaufort Group, a fossiliferous and geologically important geological Group of the Karoo Supergroup in South Africa. The thickest outcrops, reaching approximately , occur from Merweville and Leeu-Gamka in its southernmost exposures, from Sutherland through to Beaufort West where outcrops start to only be found in the south-east, north of Oudshoorn and Willowmore, reaching up to areas south of Graaff-Reinet. Its northernmost exposures occur around the towns Fraserburg and Victoria West. The Tapinocephalus Assemblage Zone is the second biozone of the Beaufort Group.
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This condition is often linked to tetrapod animals with an aquatic lifestyle, where it contributes in forming long flippers in for example modern whales, as well as in the extinct ichthyosaurs and plesiosaurs. Modern soft-shelled turtles also exhibit hyperphalangy, but though this does not result in long flippers, it may help enlarge the paddle surface and aid aquatic movement. Other aquatic and marine turtles instead have elongated limbs and phalanges, and land turtles have short limbs and feet. Jeholochelys was found to be related to coexisting sinemydid turtles, most closely to Xiaochelys and Changmachelys, and like other Cretaceous relatives, it had a low-domed shell.
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There are several different ways for aquatic tetrapod to counteract their positive buoyancy caused by their lungs: pachyostosis, osteosclerosis, pachyosteosclerosis, and calcified cartilage of bone. The ultimate goal of these processes are to increase density for different parts of the body to offset the buoyancy, in order to live in an aquatic/semi-aquatic environment. Bone histology of Pistosaurus longaevus studied by Paleontologist Krahl showed that the medullary region of humeri was filled, and it contained calcified cartilage incorporated into endoseal bone. According to Krahl, the small region of medullary of humeri is results from a suppressed perimedullary resorption activity, which is associated with osteosclerosis.
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Jeholodens was a primitive mammal belonging to the order Eutriconodonta, and which lived in present-day China during the Middle Cretaceous about 125 million years ago. Only one specimen has been formally described. This specimen (the holotype) consists of a virtually complete articulated skull and skeleton, it shared its corporal characteristics with most other Mesozoic mammals; it was a long-tailed, nocturnal tetrapod (with prehensile fingers and toes) which hunted insects, its food, during the night. Possible specimen displayed in Hong Kong Science Museum Restoration It is suspected to be a nocturnal creature because it had very large eyes which were roughly 5 cm across.
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Hepatozoon is a genus of Apicomplexa alveolates which incorporates over 300 species obligate intraerythrocytic parasites. Species have been described from all groups of tetrapod vertebrates, as well as a wide range of haematophagous arthropods, which serve as both the vectors and definitive hosts of the parasite. By far the most biodiverse and prevalent of all haemogregarines, the genus is distinguished by its unique reciprocal trophic lifecycle which lacks the salivary transmission between hosts commonly associated with other apicomplexans. While particularly prevalent in amphibians and reptiles, the genus is more well known in veterinary circles for causing a tick-borne disease called hepatozoonosis in some mammals.
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Pangolin skeletons at the Museum of Osteology (2009) Schematic drawing of pangolin scale histology The physical appearance of a pangolin is marked by large hardened overlapping plate-like scales, which are soft on newborn pangolins, but harden as the animal matures. They are made of keratin, the same material from which human fingernails and tetrapod claws are made, and are structurally and compositionally very different from the scales of reptiles. The pangolin's scaled body is comparable in appearance to a pine cone. It can curl up into a ball when threatened, with its overlapping scales acting as armor, while it protects its face by tucking it under its tail.
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Trace fossils provide us with indirect evidence of life in the past, such as the footprints, tracks, burrows, borings, and feces left behind by animals, rather than the preserved remains of the body of the actual animal itself. Unlike most other fossils, which are produced only after the death of the organism concerned, trace fossils provide us with a record of the activity of an organism during its lifetime. Trace fossils are formed by organisms performing the functions of their everyday life, such as walking, crawling, burrowing, boring, or feeding. Tetrapod footprints, worm trails and the burrows made by clams and arthropods are all trace fossils.
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By the time Tinirau appeared, many stem tetrapods had already developed the three major hindlimb bones of tetrapods: the femur, tibia, and fibula. While derived stem tetrapods like Panderichthys had hindlimb configurations very similar to the first land-living tetrapods, some early forms such as Eusthenopteron possessed a prominent postaxial process of the fibula hanging over the fibulare bone below it. Tinirau is the earliest known stem tetrapod to have a significantly reduced postaxial process, and a fibula more like those of later tetrapods. Like those of the Late Devonian Panderichthys and Ichthyostega, the glenoid of Tinirau is elongated along the anteroposterior (forward-backward) axis of the body.
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In phylogenetic terms, Tinirau is positioned more crownward, or closer to Tetrapoda, than other stem tetrapods like osteolepiforms and tristichopterids. In its first description, the phylogenetic analysis of Swartz placed Tinirau as a branch directly connected to the stem of Tetrapoda. In other words, it is a close relative of the lineage leading to land vertebrates (a prehistoric taxon can rarely be identified as an ancestor of another taxon, but is instead considered a side branch in a larger lineage). Eusthenopteron, traditionally considered a direct ancestor of tetrapods, or a close relative of such an ancestor, was placed deep within the family Tristichopteridae, away from the tetrapod stem.
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While the early amniotes resembled their amphibian ancestors in many respects, a key difference was the lack of an otic notch at the back margin of the skull roof. In their ancestors, this notch held a spiracle, an unnecessary structure in an animal without an aquatic larval stage.Lombard, R. E. & Bolt, J. R. (1979): Evolution of the tetrapod ear: an analysis and reinterpretation. Biological Journal of the Linnean Society No 11: pp 19–76 Abstract There are three main lines of amniotes, which may be distinguished by the structure of the skull and in particular the number of temporal fenestrae (openings) behind each eye.
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The group of onychodontiformes, described in 1973 by the late Dr. Mahala Andrews, was characterized by a highly kinetic skull and tusk-like teeth. Suggestions by palaeontologist John A. Long refer to a close phylogenetic relationship between Onychodus and the basal lobe-finned fish Psarolepis from China. It is generally acknowledged that Onychodus and Psarolepis are both basal bony fishes, because of the absence of major features that unite coelacanths, lungfishes and tetrapod-like lobe-finned fishes. The position of Onychodus and Psarolepis in the cladogram is outside the major clade of sarcopterygians (lobe-finned fishes), but at a position more derived than actinopterygians (ray-finned fishes).
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For example, Seymouria agilis (Olson, 1980), known from a nearly complete skeleton from the Chickasha Formation of Oklahoma, was reassigned by Michel Laurin and Robert R. Reisz to the parareptile Macroleter in 2001. Seymouria grandis, described a year earlier from a braincase found in Texas, has not been re- referred to any other tetrapod, but it remains poorly known. Langston (1963) reported a femur indistinguishable from that of S. baylorensis in Permian sediments at Prince Edward Island on the Eastern coast of Canada. Seymouria- like skeletal remains are also known from the Richards Spur Quarry in Oklahoma, as first described by Sullivan & Reisz (1999).
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Fauna of the Ischigualasto Formation The Ischigualasto Formation is highly fossiliferous and its unique paleontological characteristics made it a Lagerstätte; a stratigraphic unit containing a diverse faunal assemblage. The paleontological importance led to the establishment of the Ischigualasto Provincial Park, a UNESCO World Heritage Site since 2000. The Ischigualasto Formation contains Late Triassic (Carnian) deposits (231.4 -225.9 million years before the present), with some of the oldest known dinosaur remains, which are the world's foremost with regards to quality, number and importance. Interpretation of Saurosuchus and Hyperodapedon Rhynchosaurs and cynodonts (especially rhynchosaur Hyperodapedon and cynodont Exaeretodon) are by far the predominant findings among the tetrapod fossils in the park.
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The tetrapod fossils recovered in the 1997–99 expedition confirmed the Isalo II was Triassic in age, but instead suggested a younger Carnian age. The age of the formation has also been correlated to the Santacruzodon Assemblage Zone (AZ) from the Santa Maria Formation in South America based on the shared genera of traversodontid cynodonts, with a similar late Ladinian or early Carnian age. The Santacruzodon AZ has been more reliably dated through radioisotope U—Pb dating, suggesting a maximum depositional age of 237 ±1.5 million years in the early Carnian. The bone bed contained material from almost "a dozen" individuals of varying ages and size, all from a single species.
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The Fram Formation is an Upper Devonian sequence of rock strata on Ellesmere Island that came into prominence in 2006 with the discovery in its rocks of examples of the transitional fossil, Tiktaalik, a sarcopterygian or lobe- finned fish showing many tetrapod characteristics. The Fram Formation is a Middle to Upper Devonian clastic wedge forming an extensive continental facies consisting of sediments derived from deposits laid down in braided stream systems that formed some 375 million years ago,Fossil pollen suggest that these rocks lie within the early and middle Frasnian Stage of the Devonian. at a time when the North American craton ("Laurentia") was straddling the equator.
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These include: peg-shaped teeth in the front of the mouth, as well as broad blunt teeth used to more effectively process vegetation. Tseajaia campi is a very rare taxon known from one nearly complete specimen recovered from the Organ Rock. Originally described by Vaughn, this animal was first assigned to the group Seymouriamorpha, however, upon reassessment of the holotype it was demonstrated to have a closer affinity to Diadectomorpha.Sumida, Stuart S., Lombard, R. E., and Berman, D. S, 1992, Morphology of the atlas axis complex of the late Palaeozoic tetrapod suborders Diadectomorpha and Seymouriamorpha: Philosophical Transactions of the Royal Society of London, v.
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Mark Tucker (born October 11, 1957 in Laurel, Maryland, and who legally changed his name in 1991 to T. Storm Hunter) is a musician, and co-founder of Tetrapod Spools. His debut album, Batstew, which is now collectible, was released in two runs, each of 100 copies. There was also one personalized edition for his girlfriend of the time, Eva Bataszew, whose title was Bataszew. The album was re-released in 1996 as a compact disc, with extra tracks that never made it onto the original LP. It comprises amongst other things recordings of Tucker's car, a 1964 Cadillac which he had nicknamed "The Bat".
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This latter interpretation has usurped the "orthodox" interpretation and is currently more widespread among paleontologists Although the generally large size of fish postparietals are inconsistent with the smaller postparietals of tetrapods, there are many factors supporting the identification of the large posterior midline elements as postparietals, rather than parietals. These include their contact with tabulars and supratemporals, the fact that they are positioned behind the bones which surround the parietal foramen (i.e. the parietal bones), and how transitional taxa show apparent homology with tetrapod postparietals and the large posterior midline elements of fish. Studies of Ichthyostega, Elpistostege, and Edops in particular have demonstrated this concept.
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Gerhart and Kirschner give the example of the evolution of a bird or bat wing from a tetrapod forelimb. They explain how, if bones undergo regulatory change in length and thickness as a result of genetic mutation, the muscles, nerves and vasculature will accommodate to those changes without themselves requiring independent regulatory change. Studies of limb development show that muscle, nerve, and vascular founder cells originate in the embryonic trunk and migrate into the developing limb bud, which initially contains only bone and dermis precursors. Muscle precursors are adaptable; they receive signals from developing dermis and bone and take positions relative to them, wherever they are.
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The Stanocephalosaurus have at least 100 straight and conical teeth on the premaxilla and maxilla combined, gradually increasing in size towards the front. Other skull regions previously inaccessible or too poorly preserved on the Stanocephalosaurus have been observed with X-ray micro-CT scans, including the otic capsule, delta groove of the exoccipital, as well as parts of the arterial and nervous system. Air pockets around the stapes of Stanocephalosaurus have been hypothesized to act as resonance chambers, meaning that the spoon-shaped inner ear bone could be related to underwater hearing. This trait is possibly associated with early tetrapod evolution, and can act as a link to Anuran tympanum evolution.
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I. Mead, D.W. Steadman, et al., "New extinct Mekosuchine crocodile from Vanuatu, South Pacific", Copeia, 2002.3: "the extinction of M. kalpokasi and other insular mekosuchines may have been anthropogenic"); . The species of this genus were small in size, 2 m in maximum length, and terrestrial, making them the last surviving group of fully terrestrial crocodilians, leaving only semi- terrestrial species such as the Cuban crocodile and the dwarves Osteolaemus and Paleosuchus.Darren Naish, "Tetrapod Zoology" (Scientific American blog): "Dissecting a crocodile", 2012 Fossils of related mekosuchines, such as Trilophosuchus, have been found from Miocene Australia (the earliest known mekosuchine is the Eocene genus Kambara), while Quinkana survived until the arrival of humans.
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Such eyelid ossicles are currently not known in any other amniotes, but have been found in some dissorophid temnospondyl amphibians, a non-amniote tetrapod group that is not closely related to synapsids. The eyelid ossicles in Ascendonanus may have evolved independently or may be an ancient feature retained from the earliest tetrapods. Such eyelid ossicles are distinct from the rod-like dermal bones, called palpebral bones, that evolved above the eye socket in a number of later non-synapsid groups, including some ornithischian dinosaurs. The pointed teeth are slender, without flattened cross-sections, serrations, or a cutting edge, and are moderately recurved in the upper jaw and straighter in the lower jaw.
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Romer 1966Carroll 1988 However, the dissolution of "labyrinthodonts" into separate groups such as temnospondyls and anthracosaurs has cast doubt on these traditional amphibian subclasses. Marjanovic & Laurin 2009 tree from SOM Much like "Labyrinthodontia", some studies proposed that Lepospondyli is an artificial (polyphyletic) grouping with some members closely related to extinct stem tetrapod groups and others more closely related to modern amphibians or reptiles.Benton 2000 Early phylogenetic analyses conducted in the 1980s and 1990s often maintained the idea that lepospondyls were paraphyletic, with nectrideans close to colosteids and microsaurs close to temnospondyls, which were considered to be ancestral to modern amphibians. However, a 1995 paper by Robert Carroll argued that lepospondyls were actually a monophyletic group closer to reptiles.
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Some lobe-finned fishes, like the extinct Tiktaalik, developed limb-like fins that could take them onto land A tetrapod (Greek for four feet) is a vertebrate with limbs (feet). Tetrapods evolved from ancient lobe-finned fishes about 400 million years ago during the Devonian Period when their earliest ancestors emerged from the sea and adapted to living on land. This change from a body plan for breathing and navigating in gravity-neutral water to a body plan with mechanisms enabling the animal to breath in air without dehydrating and move on land is one of the most profound evolutionary changes known. as PDF Tetrapods can be divided into four classes: amphibians, reptiles, birds and mammals.
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The principle of homology: The biological relationships (shown by colours) of the bones in the forelimbs of vertebrates were used by Charles Darwin as an argument in favor of evolution. In biology, homology is similarity due to shared ancestry between a pair of structures or genes in different taxa. A common example of homologous structures is the forelimbs of vertebrates, where the wings of bats and birds, the arms of primates, the front flippers of whales and the forelegs of four-legged vertebrates like dogs and crocodiles are all derived from the same ancestral tetrapod structure. Evolutionary biology explains homologous structures adapted to different purposes as the result of descent with modification from a common ancestor.
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The environment of Las Hoyas dates to the Barremian, and it was probably a tropical or subtropical wetland habitat, based on its vegetation: Bennettitales, Brachyphyllum, Pagiophyllum, Sphenolepis and Cupressinocladus conifers, Weitchselia reticulata, Montsechia vidali and several others. Various species of fish and aquatic invertebrates are also known.Fossilworks: Las Hoyas Crocodylomorphs are the most common tetrapod fossils, bearing a wide variety of species from familiar semi-aquatic species as well as terrestrial forms like gobiosuchids and atoposaurids, the latter probably having competed with mammals. Non-avian dinosaurs are present in the form of Pelecanimimus and Mantellisaurus, but the site is more notable for a variety of enantiornithe birds like Iberomesornis, Concornis and Eoalulavis.
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Pederpes was 1 m long, making it average-sized for an early tetrapod. The shape of the skull and the fact that the feet face forward rather than outward indicate that Pederpes was well adapted to land life. It is currently the earliest known fully terrestrial animal, although the structure of the ear shows that its hearing was still much more functional underwater than on land, and may have spent much of its time in the water and could have hunted there. The narrow skull suggests that Pederpes breathed by inhaling with a muscular action like most modern tetrapods, rather than by pumping air into the lungs with a throat pouch the way many modern amphibians do.
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Common toad (Bufo bufo) swimming Most of the Amphibia have a larval state, which has inherited anguilliform motion, and a laterally compressed tail to go with it, from fish ancestors. The corresponding tetrapod adult forms, even in the tail-retaining sub-class Urodeles, are sometimes aquatic to only a negligible extent (as in the genus Salamandra, whose tail has lost its suitability for aquatic propulsion), but the majority of Urodeles, from the newts to the giant salamander Megalobatrachus, retain a laterally compressed tail for a life that is aquatic to a considerable degree, which can use in a carangiform motion.Lighthill , MJ. Hydromechanics of Aquatic Animal Propulsion- Annu. Rev. Fluid. Mech. - 1969 1-413-446.
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The number of digits on hands and feet became standardized at five, as lineages with more digits died out. Thus, those very few tetrapod fossils found in this "gap" are all the more prized by palaeontologists because they document these significant changes and clarify their history. The transition from an aquatic, lobe-finned fish to an air- breathing amphibian was a significant and fundamental one in the evolutionary history of the vertebrates. For an organism to live in a gravity-neutral aqueous environment, then colonize one that requires an organism to support its entire weight and possess a mechanism to mitigate dehydration, required significant adaptations or exaptations within the overall body plan, both in form and in function.
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250px In tetrapod anatomy, lumbar is an adjective that means of or pertaining to the abdominal segment of the torso, between the diaphragm and the sacrum. The lumbar region is sometimes referred to as the lower spine, or as an area of the back in its proximity. In human anatomy the five lumbar vertebrae (vertebrae in the lumbar region of the back) are the largest and strongest in the movable part of the spinal column, and can be distinguished by the absence of a foramen in the transverse process, and by the absence of facets on the sides of the body. In most mammals, the lumbar region of the spine curves outward.
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The only other fossil assemblage that shows similarities with the Moradi assemblage is that of the Ikakern Formation in Morocco, which includes a late-surviving species of the lepospondyl amphibian Diplocaulus, an unnamed large captorhinid, and the pareiasaur Arganaceras. Studies of the sediments of the Moradi Formation show that the region was extremely arid during the Late Permian but had a shallow groundwater table that could support plant and animal life. Climate models of the Late Permian suggest that this arid region extended across much of central Pangaea. The Moradi Formation may have been a refugium for many tetrapods that were once diverse earlier in the Permian but had been replaced elsewhere on the supercontinent by new tetrapod faunas.
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As with all other arthrodires, Groenlandaspis had a joint in the back of its head with its thoracic armor, allowing for its head to be thrown back, increasing its gape. However, as its head is somewhat compressed in comparison with many other arthrodires, and as the dorsal side came to a low, pyramid-like peak, it is believed that Groenlandaspis could not throw its head back very far. It was a relatively small fish, only in length,though G. riniensis reached almost a metre in length Gess, Robert W.; Whitfield, Alan K. (August 22, 2020). "Estuarine fish and tetrapod evolution: insights from a Late Devonian (Famennian) Gondwanan estuarine lake and a southern African Holocene equivalent".
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A four-month expedition spanning 1964 and 1965 in the Ischigualasto-Villa Unión Basin of La Rioja Province, Argentina was conducted by Alfred Romer and his colleagues, who consisted of researchers from the Museum of Comparative Zoology (MCZ) at Harvard University. While the first two months of the expedition were unfruitful, excavations near the Chañares River and the Gualo River, soon uncovered specimens belonging to a wide variety of tetrapod groups. Among these was the skeleton of a small suchian archosaur, discovered about north of the Chañares River. The skeleton was stored at the La Plata Museum (MLP), which had supported the expedition, under the specimen number MLP 64-XI-14-11.
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Across eusthenopterids (tristichopterids), a trend exists showing increasingly higher values for this ratio in more derived genera with Eusthenodon possessing the highest value with a frontoethmoidal shield to parietal shield ratio of 2.30. The further expansion of snout length in many tetrapod species may also be further evidence supporting the tendency of increasingly longer frontoethmoidal shields present in subsequent clades closely related to eusthenopterids including the late eopods. The orbital fenestrae housing the small eyes of Eusthenodon were distinctly smaller in size compared to the size of the larger frontoethmoidal shield. Residing posteriorly to the orbital fenestra, the posterior supraorbital bone extends downwards along the fenestra and comes into contact with lachrymal.
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Tetrapods such as temnospondyl amphibians, diapsid reptiles, and dicynodont therapsids are common in the Late Permian and seemed to have recovered by the Middle Triassic, but there is little record of their presence in the Early Triassic. All of these tetrapods are present in Early Triassic strata of the Fremouw Formation, suggesting that Antarctica served as a refugium for these animals. During the extinction, global temperatures rose and the supercontinent Pangea moved northward, putting pressure on populations that could not adapt to the warming climate. Antarctica, while much warmer in the Early Triassic than it is today, was cooler than other parts of Gondwana and may have been more hospitable to tetrapod populations.
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This outcrop is currently assigned to the upper part of the Usili Formation, formerly known as the Kawinga Formation, of the Songea Group of the Ruhuhu Basin. Recent studies have described this formation as a 260 meters thick fluviolacustrine succession made up of a lowermost conglomeratic interval that is approximately 5 meters thick, grading up into a trough cross- bedded, coarse-grained, sandstone-dominated interval that is 25–40 meters thick, overlain by massive nodular siltstone and laminated mudstone beds with minor ribbon sandstones forming the bulk of the succession. Sidor et al. (2010) recognized only one tetrapod faunal assemblage in the Usili Formation, which includes, in addition to Aenigmastropheus, temnospondyls, pareiasaurs, gorgonopsians, therocephalians, cynodonts, and dicynodonts.
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Also, the absence of lateral line sulci on the roof of the skull and the well ossified qualities of the postcranial skeleton also support the notion that they had a terrestrial life. The primitive tetrapod, Acanthostega gunnari (Jarvik, 1952), presents a direct biting of prey feeding mechanism and demonstrates the terrestrial mode of feeding. Unlike most terrestrial feeders among temnospondyli, Chenoprosopus, which lived in dry environments, displayed weaker bite capabilities than Nigerpeton, which presents strong bite capabilities. The skull of Chenoprosopus presented stresses in the posterior part of the skull than in the rest of the skull because of weak bite capabilities that could be the adductor musculature beneath the squamosal bones.
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The second species of this genus is Mesenosaurus efremovi. Its nearly complete skull and mandible was discovered at Richards Spur locality within a series of infilled karst fissures in the Ordovician Arbuckle limestone in Oklahoma, which is one of the most plentiful sites for early Permian tetrapod fossils. In terms of classifying M. efremovi, it shares distinct cranial features with mycterosaurines (stem based group that includes Mycterosaurus longiceps and all varanopseids related more closely to it than to Varanodon agilis), such as the “exclusion of the lacrimal from the external naris and an anteroposteriorly broad dorsal lamina of the maxilla that underlies the nasal and contacts the prefrontal”. However, M. efremovi shares more features with M. romeri from Russia.
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Shaped concrete armour units (such as Dolos, Xbloc, Tetrapod, etc.) can be provided in up to approximately 40 tonnes (e.g. Jorf Lasfar, Morocco), before they become vulnerable to damage under self weight, wave impact and thermal cracking of the complex shapes during casting/curing. Where the very largest armour units are required for the most exposed locations in very deep water, armour units are most often formed of concrete cubes, which have been used up to ~195 tonnes for the tip of the breakwater at Punta Langosteira near La Coruña, Spain. Preliminary design of armour unit size is often undertaken using the Hudson Equation, Van der Meer and more recently Van Gent et al.
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Tetrapod forelimbs are characterised by a high degree of mobility in the shoulder- thorax connection. Lacking a solid skeletal connection between the shoulder girdle and the vertebral column, the forelimb's attachment to the trunk is instead mainly controlled by serratus lateralis and levator scapulae. Depending on locomotor style, a bone connects the shoulder girdle to the trunk in some animals; the coracoid bone in reptiles and birds, and the clavicle in primates and bats; but cursorial mammals lack this bone. In primates, the shoulder shows characteristics that differ from other mammals, including a well developed clavicle, a dorsally shifted scapula with prominent acromion and spine, and a humerus featuring a straight shaft and a spherical head.
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Tutusius is a genus of extinct tetrapod from the Devonian of South Africa, containing a single species, Tutusius umlambo. It was described from the +/- 360 myo Gondwana locality of Waterloo Farm lagerstätte on the south-eastern coast of South Africa, which at the time was located within the Antarctic Circle. Together with the find of Umzantsia amazana from the same locality, this provides the first evidence that Devonian tetrapods were not restricted to the tropics as was formerly believed, and suggests that they may have been global in distribution. Waterloo Farm fossils have been metamorphosed and intensely flattened, with the bone tissue replaced by secondary metamorphic mica that is partially altered to kaolinite and chlorite during uplift.
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Umzantsia is a genus of extinct tetrapod from the Devonian of South Africa, containing a single species, Umzantsia amazana. It was described from the +/- 360 myo Gondwana locality of Waterloo Farm lagerstätte on the south-eastern coast of South Africa, which at the time was located within the Antarctic Circle. Together with the find of Tutusius umlambo from the same locality, this provides the first evidence that Devonian tetrapods were not restricted to the tropics as was formerly believed, and suggests that they may have been global in distribution. Waterloo Farm fossils have been metamorphosed and intensely flattened, with the bone tissue replaced by secondary metamorphic mica that is partially altered to kaolinite and chlorite during uplift.
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The Omingonde Formation is part of the Karoo Supergroup, which preserves many Triassic tetrapod fossils in southern Africa but notably lacks fossils in a hiatus called the "Ladinian gap". In addition to the remains of Stahleckeria potens, fossils of the cynodont Chiniquodon and an unidentified rauisuchian have also been found in the Omingonde deposits. The presence of these animals in South America and in Africa at the same time is strong evidence that the two continents were once one uninterrupted landmass with a uniform climate and habitat that land animals such as Stahleckeria could travel freely between. The fossils of Stahleckeria potens discovered in Brazil are currently in Germany in the museum of the University of Tübingen.
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Restoration Model reconstruction at the State Museum of Natural History in Stuttgart, Germany Skull 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 forelimb. The front foot of Acanthostega could not bend forward at the elbow, and therefore could not be brought into a weight bearing position, appearing to be more suitable for paddling or for holding on to aquatic plants. Acanthostega is the earliest stem-tetrapod to show the shift in locomotory dominance from the pectoral girdle to the pelvic girdle.
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Some of the sandstone layers have been given informal names, such as the Red Tank and Brushy Creek Sandstone Members. Limestone layers are rare relative to the "southern area", and the diagnostic Taylor County layers are seemingly completely absent north of the Salt Fork, although a dolomite layer possibly equivalent to the Rainey or Lytle limestones has been reported. This dolomite layer, informally named the Craddock dolomite, has been known to preserve plant impressions as well as arthropod and tetrapod footprints. With the absence of the characteristic Standpipe Limestone of the "southern area", Arroyo red beds in the "classic area" are difficult to differentiate from the overlying Vale Formation on a purely geological basis.
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Nevertheless, Olson admitted that this boundary was imprecise due to the variable depth of the shales and the varying topography of the surrounding landscape. Dimetrodon grandis found at the Craddock bonebed on display at the National Museum of Natural History The "classic area" of the Arroyo Formation is one of the most fossiliferous parts of the Texas Red Beds, and it is typically differentiated from surrounding formations by paleontologists on the basis of faunal differences. A large number of sites are known bearing either abundant plant or animal remains. The animal-bearing sites are among the most diverse Early Permian tetrapod assemblages in the world, with numerous remains of amphibians, pelycosaurs (mammal relatives), chondrichthyans (sharks), and eureptiles.
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No convincing evidence for sexual dimorphism in body size or mating signals is known in ceratopsids, although there is evidence that the more primitive ceratopsian Protoceratops andrewsi possessed sexes that were distinguishable based on frill and nasal prominence size. This is consistent with other known tetrapod groups where midsized animals tend to exhibit markedly more sexual dimorphism than larger ones. However, it has been proposed that these differences can be better explained by intraspecific and ontogenic variation rather than sexual dimorphism. In addition, many sexually dimorphic traits that may have existed in ceratopsians include soft tissue variations such as coloration or dewlaps, which would be unlikely to have been preserved in the fossil record.
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Tetrapod fossils have been found only in the lower lithologic unit of the Chañares Formation, where they are preserved almost exclusively within carbonate concretions. Fossilized bone preserved in concretion shows some of the best form of preservation, with dark brown bone surfaces exhibiting virtually no evidence of macroscopic weathering. The fossil accumulations of the Chañares assemblage are considered to be the product of two different taphonomic pathways: attritional accumulation associated with natural deaths of individuals by predation, disease and old age, and mass mortality of animals associated with volcanic events. In the mass mortality event, there is a clear bias towards preservation of individuals representing smaller-sized to mid-sized taxa such as Massetognathus.
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The Tetrapodomorpha (also known as Choanata) are a clade of vertebrates consisting of tetrapods (four-limbed vertebrates) and their closest sarcopterygian relatives that are more closely related to living tetrapods than to living lungfish. Advanced forms transitional between fish and the early labyrinthodonts, such as Tiktaalik, have been referred to as "fishapods" by their discoverers, being half-fish, half-tetrapods, in appearance and limb morphology. The Tetrapodomorpha contains the crown group tetrapods (the last common ancestor of living tetrapods and all of its descendants) and several groups of early stem tetrapods, which includes several groups of related lobe- finned fishes, collectively known as the osteolepiforms. The Tetrapodamorpha minus the crown group Tetrapoda are the Stem Tetrapoda, a paraphyletic unit encompassing the fish to tetrapod transition.
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George Frederick Matthew, a pioneer in the field of ichnology also took an interest in Joggins and published his observations on tetrapod trackways recovered from the site in 1903. Walter A. Bell began researching the Joggins Formation in 1911, almost immediately after his graduation from Yale University. Bell was one of Canada's delegates at International Geological Congress's twelfth meeting in 1913, and accompanied the other delegates on a tour and dinner at the Joggins Cliffs that year. In 1914, Bell conducted the first detailed study of macrofloral fossils across Nova Scotia's Carboniferous formations, including the Mabou Group and Cumberland Group; as part of this study Bell assigned Divisions III, IV, and V (and part of Division II) to the "Joggins Formation", the first use of the name.
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Life restoration of Palaeomolgophis Similar to various other lepospondyls, adelospondyls lost several bones in the temporal region of the skull, which is at the back of the skull between the quadratojugal bone of the jaw joint and the parietal and postparietal bones at the midline of the skull roof. Stem- and crown-tetrapods typically have three to four bones on each side of the skull in this region (from top to bottom): the tabular, supratemporal (and sometimes an adjacent intertemporal), and squamosal. The intertemporal is lost (or fused into other bones) in a variety of unrelated tetrapod groups. The same process additionally occurs to the supratemporal in several lepospondyls, namely "microsaurs" and a few "nectrideans" such as Scincosaurus and diplocaulids.
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There is no evidence that it did so, only that it may have been anatomically capable of doing so. The publication in 2018 of Tutusius umlambo and Umzantsia amazana from high latitude Gondwana setting indicate that the tetrapods enjoyed a global distribution by the end of the Devonian and even extend into the high latitudes. The end-Fammenian marked another extinction, known as the end-Fammenian extinction or the Hangenberg event, which is followed by another gap in the tetrapod fossil record, Romer's gap, also known as the Tournaisian gap. This gap, which was initially 30 million years, but has been gradually reduced over time, currently occupies much of the 13.9-million year Tournaisian, the first stage of the Carboniferous period.
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One of the earliest notable events in Pennsylvania paleontology was the October 5th, 1787 presentation by Caspar Wistar and Timothy Matlack of a probable dinosaur metatarsal discovered in Late Cretaceous rocks near Woodbury Creek in New Jersey as "'a large thigh bone'" to the American Philosophical Society in Philadelphia. During the industrial revolution, Carboniferous-aged coal deposits in Pennsylvania were the sites of serendipitous discoveries of early fossil tetrapod trackways. Such discoveries generally occur when the excavation of coal mines removes the rock underlying the trackway, leaving it exposed on the tunnel's ceiling. Later, during the 1840s, Charles Lyell examined some local purported fossil bird and mammal tracks and found that they were actually petroglyphs left by local indigenous people.
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It has been suggested that the evolution of the tetrapod limb from fins in lobe-finned fishes is related to expression of the HOXD13 gene or the loss of the proteins actinodin 1 and actinodin 2, which are involved in fish fin development. Robot simulations suggest that the necessary nervous circuitry for walking evolved from the nerves governing swimming, utilizing the sideways oscillation of the body with the limbs primarily functioning as anchoring points and providing limited thrust. This type of movement, as well as changes to the pectoral girdle are similar to those seen in the fossil record can be induced in bichirs by raising them out of water. A 2012 study using 3D reconstructions of Ichthyostega concluded that it was incapable of typical quadrupedal gaits.
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A common theme that has been identified in all tetrapods, including humans and microbats: (1) a respiratory system with lungs; (2) a vocal tract that filters emitted sound before it exits into the surrounding environment; and (3) every tetrapod has a larynx that quickly closes to function in protection of the lungs, as well as it often might function in phonation, as is the case in humans and microbats. One feature of the mammal vocalization system that results in variation of sound production, especially for microbats and megabats, is the length of vocal folds. The vocal folds determine the lowest frequency at which the folds can vibrate. Compared to humans, the length of vocal folds in microbats is very short.
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Based on their position in Homalocephale, the ossified tendons found with UALVP 2 would have formed an intricate "" in the tail, consisting of parallel rows, with the extremities of each tendon contacting the next successively. Such structures are called , and are otherwise only known in teleost fish; the feature is unique to pachycephalosaurs among tetrapod (four- limbed) animals, and may have functioned in stiffening the tail. Life restoration of S. validum, with integument based on other small ornithischian dinosaurs The scapula (shoulder blade) was longer than the humerus (upper arm bone); its blade was slender and narrow, and slightly twisted, following the contour of the ribs. The scapula did not expand at the upper end but was very expanded at the base.
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In addition to these early trackways providing additional evidence of tetrapod activity on land as early as the Devonian, recent work has also been aimed at gleaning biomechanical interpretations from these occurrences. Typically, it is assumed that the earliest tetrapods had a movement pattern very similar to modern amphibians where the entirety of the pectoral and pelvic girdles would swing as the animal moved forward causing the angular pattern seen in these trackways. Although this movement is quite common in animals such as salamanders, recent work has also been done showing similar patterns created by terrestrially locomoting actinopterygian and sarcopterygian fish. In animals such as the actinopterygian cavefish, the alternating footfalls and general layout of the ancient trackways was readily reproduced.
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The Cenozoic world has seen great diversification of bony fishes, amphibians, reptiles, birds and mammals. Over half of all living vertebrate species (about 32,000 species) are fish (non- tetrapod craniates), a diverse set of lineages that inhabit all the world's aquatic ecosystems, from snow minnows (Cypriniformes) in Himalayan lakes at elevations over to flatfishes (order Pleuronectiformes) in the Challenger Deep, the deepest ocean trench at about . Fishes of myriad varieties are the main predators in most of the world's water bodies, both freshwater and marine. The rest of the vertebrate species are tetrapods, a single lineage that includes amphibians (with roughly 7,000 species); mammals (with approximately 5,500 species); and reptiles and birds (with about 20,000 species divided evenly between the two classes).
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A partial Ventastega cheekplate consisting of the jugal, and parts of the lacrimal, quadratojugal, squamosal, and preopercular is convex in the vertical plane, indicating that Ventastega's skull was low in height. The preopercular in this specimen and several other partial skull fragments is a primitive tetrapod character, otherwise seen only in Ichthyostega, Acanthostega, and Crassigyrinus. The cephalic lateral lines in Ventastega have an intermediate morphology with the lines only being partially enclosed, between the primitive state of full enclosure of the lines in fish and Ichthyostega, and the fully open lines seen in Temnospondyls and other derived tetrapods. The ventral surface of the Ventastega pterygoid is covered is covered in denticles, a feature shared by all early tetrapods except Ichthyostega.
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The clavicle has a broad ventral blade with a narrow stem, characteristic of early tetrapods, along with the stem having a thick anterior and thin posterior lamina that merges into the lateral rod surface. In the iliac blade, there is a pronounced bend/kink approximately one third from the proximal end of the blade, with the distal part of the blade bent dorsally and mesially. The interclavicle is approximately 25% smaller than the clavicle, and similar in shape in a Greererpeton interclavicle, suggesting it had a similar rhomboidal or kite shape. The clavicle itself is similar to the morphology of other early tetrapod clavicles, with a tapering clavicular stem and P-shaped cross section, although it has a unique and distinct unornamented strip along the anterior margin.
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Theriognathus is represented by abundant occurrences in the Karoo Basin of South Africa, sequestered records in the Upper Permian Ruhuhu Basin of Tanzania, Zambia, and Russia. Late Permian therapsids are best known from the Karoo Basin, which covers a massive area and provides Permian sediments that total 12 km in thickness. During the Late Permian, sediments were fed into the Karoo Basin from a ring of mountains that encircled Southern Gondwana (an ancient supercontinent, partly located on what is now South America and Antarctica) In the Karoo is the Beaufort Group, a subdivision of the basin. This division is further broken down into assemblage zones, intervals of geological strata that are defined based on the distributions of previously found tetrapod taxa.
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The dentition of Spathicephalus is so unusual that isolated jaw fragments with teeth in them can easily be identified. Although the species S. pereger is only known by a partial skull roof, paleontologist Donald Baird assigned it to Spathicephalus with confidence because the shapes of its bones closely matched the corresponding bones in S. mirus. One of the few differences that separate S. pereger from S. mirus is the reticulate or "honeycomb" ornamentation on its skull roof, characterized by pits and grooves. The pustular ornamentation seen in S. mirus is in fact rare among early tetrapods (plagiosaurid temnospondyls and the very early tetrapod Ichthyostega are some of the few to have them), while the reticulate ornamentation of S. pereger is more typical.
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Early four-limbed vertebrates are sometimes referred to as tetrapods (using a trait-based definition of the term), although animals like Hynerpeton, Ichthyostega, and Acanthostega are placed outside the crown group Tetrapoda by the vast majority of paleontologists. From a cladistic (relations-based) point of view, a more accurate term would be "stem-tetrapod" or "stegocephalian", indicating that they were part of the lineage of animals that would lead to true tetrapods such as modern amphibians (Lissamphibia), reptiles, mammals, and birds. Hynerpeton hails from the Red Hill fossil site, which, during the Late Devonian, was a warm floodplain inhabited by a diverse ecosystem of aquatic fish and terrestrial invertebrates. Hynerpeton was one of several genera of four-limbed vertebrates known from the site, although it was the first to be discovered.
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While Hynerpeton is a tetrapod in the sense that it is a four-limbed vertebrate, it is not a member of the clade Tetrapoda because its lineage went extinct long before the lineages of modern tetrapods evolved. Likewise, "Ichthyostegalia" has been abandoned in the age of cladistics due to being an evolutionary grade leading to true tetrapods, rather than a relations-based clade. The traditional, non- cladistic definition of Tetrapoda, which begins at the earliest limbed vertebrates, corresponds closely to a clade named Stegocephalia, which is defined as all animals more closely related to temnospondyls than to Pandericthys. Hynerpeton has not been included in many phylogenetic analyses, but those that have included it usually place it as a transitional form on a series of stem-tetrapods leading to Tetrapoda.
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The supraorbital groove begins abruptly on the dorsal surface of the premaxilla, immediately passes on to the nasal, and extends back on that bone close to its suture with the lachrymal. It then comes on to the prefrontal, passing on to the frontal where that bone enters the orbital border. Then as a well-defined groove it surrounds the hinder part of the orbit, turns vertically on to the jugal, and then backward to cross the point where jugal, quadratojugal and squamosal meet, continuing over the squamosal to pass back on to the body. Xenotosuchus skull, showing the full complement of tetrapod skull roof bones Xenotosuchus is a member of this which is not very well known, and only a few fragments have been discovered from this animal.
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He has also conducted research on dinosaur material from Mongolia and tetrapod-bearing deposits in Sudan. Evans has also been involved with both fieldwork and research of the Early Jurassic sauropodomorph Massospondylus from South Africa and has conducted research on pelycosaurian-grade Permian synapsids, Permian temnospondyls, the iconic Pleistocene felid Smilodon, and choristoderes. Evans has been a part of various teams that have named over a dozen new genera or species of dinosaurs. New ceratopsians named by Evans and colleagues include Xenoceratops foremostensis Ryan, Evans, & Shepherd, 2012; Gryphoceratops morrisoni Ryan, Evans, Currie, Brown, & Brinkman, 2012; Unescoceratops koppelhusi Ryan, Evans, Currie, Brown, & Brinkman, 2012; Mercuriceratops gemini Ryan, Evans, Loewen, & Currie, 2014; Wendiceratops pinhorensis Evans & Ryan, 2015; Spiclypeus shipporum Mallon, Ott, Larson, Iuliano, & Evans, 2016; and Ferrisaurus sustutensis Arbour & Evans, 2019.
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All tetrapod forelimbs are homologous, evolving from the same initial structures in lobe-finned fish. However, another distinct process may be identified, convergent evolution, by which the wings of birds, bats, and extinct pterosaurs evolved the same purpose in drastically different ways. These structures have similar form or function but were not present in the last common ancestor of those groups. Bat wings are composed largely of a thin membrane of skin supported on the five fingers, whereas bird wings are composed largely of feathers supported on much reduced fingers, with finger 2 supporting the alula and finger 4 the primary feathers of the wing; there are only distant homologies between birds and bats, with much closer homologies between any pair of bird species, or any pair of bat species.
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Casts of Amargasaurus and Carnotaurus, both discovered by the same 1984 expedition in Argentina, Natural History Museum of the University of Pisa The only known skeleton (specimen number MACN-N 15) was discovered in February 1984 by Guillermo Rougier during an expedition led by Argentine paleontologist José Bonaparte. This was the eighth expedition of the project "Jurassic and Cretaceous Terrestrial Vertebrates of South America", which was supported by the National Geographic Society and initiated in 1975 to improve on the sparse knowledge of the Jurassic and Cretaceous tetrapod life of South America. The same excursion uncovered the nearly complete skeleton of the horned theropod Carnotaurus. The discovery site is located in the La Amarga arroyo in the Picún Leufú Department of Neuquén Province in northern Patagonia, south of Zapala.
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Although it appears to have spent its whole life in water, its humerus also exhibits traits that resemble those of later, fully terrestrial stem-tetrapods (the humerus in Ichthyostega being somewhat derived from, and homologous with the pectoral and pelvic fin bones of earlier fishes). This could indicate that vertebrates evolved terrestrial traits earlier than previously assumed, and numerous times independently from another.Fossils suggest earlier land-water transition of tetrapod Research based on analysis of the suture morphology in the skull of Acanthostega indicates that the species was able to bite prey at or near the water's edge. Markey and Marshall compared the skull with the skulls of fish, which use suction feeding as the primary method of prey capture, and creatures known to have used the direct biting on prey typical of terrestrial animals.
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Walter Gross was the first person to collect partial Ventastega remains, collecting some teeth in addition to scales from a locality called Ketleri in a Latvian Upper Famennian formation while on a collection trip in 1933. Gross attributed all remains to an osteolepiform fish named Polyplocodus wenjukov, before later in 1944 reattributing some of the fragments to a species called Panderichthys bystrowi when a piece of a lower jaw was collected from the same locality. Additional remains were collected from the locality and from another locality, Pavāri, in the same formation by researchers Per Erik Ahlberg, Ervīns Lukševičs, and Oleg Lebedev. After this collection they realized the previously collected remains were assigned incorrectly, and were actually part of a newly discovered tetrapod, which they named and described in a paper published in 1996.
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He entered zealously into the geology of Canada, making a special study of the fossil forests of the coal-measures of Joggins, Nova Scotia, now a UNESCO World Heritage Site. During the course of his second exploration of the cliffs with Charles Lyell in 1852, he discovered the remains of a tetrapod named Dendrerpeton entombed within a fossil tree. Over the years, he continued his exploration of the fossil trees, eventually unearthing the oldest known reptile in the history of life, which he named Hylonomus lyelli in honour of his mentor. From 1855 to 1893 he was professor of geology and principal of McGill University in Montreal, an institution which under his influence attained a high reputation. In 1859 he published a seminal paper describing the first fossil plant found in rocks of Devonian origin.
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Tetrapod legs evolved in the Devonian or Carboniferous geological period from the pectoral fins and pelvic fins of their crossopterygian fish ancestors. Fish fins develop along a "fin line", which runs from the back of the head along the midline of the back, round the end of the tail, and forwards along the underside of the tail, and at the cloaca splits into left and right fin lines which run forwards to the gills. In the paired ventral part of the fin line, normally only the pectoral and pelvic fins survive (but the Devonian acanthodian fish Mesacanthus developed a third pair of paired fins); but along the non-paired parts of the fin line, other fins develop. In tetrapods, only the four paired fins normally persisted, and became the four legs.
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Diagram showing nasal chambers inside the snout (AMNH 5895) In 1977 the Polish paleontologist Teresa Maryańska proposed that the complex sinuses and nasal cavities of ankylosaurs may have lightened the weight of the skull, housed a nasal gland, or acted as a chamber for vocal resonance. Carpenter rejected these hypotheses, arguing that tetrapod animals make sounds through the larynx, not the nostrils, and that reduction in weight was minimal, as the spaces only accounted for a small percent of the skull volume. He also considered a gland unlikely and noted that the sinuses may not have had any specific function. It has also been suggested that the respiratory passages were used to perform a mammal-like treatment of inhaled air, based on the presence and arrangement of specialized bones.
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Eubrontes, a dinosaur footprint in the Lower Jurassic Moenave Formation at the St. George Dinosaur Discovery Site at Johnson Farm, southwestern Utah Fossil footprints made by tetrapod vertebrates are difficult to identify to a particular species of animal, but they can provide valuable information such as the speed, weight, and behavior of the organism that made them. Such trace fossils are formed when amphibians, reptiles, mammals or birds walked across soft (probably wet) mud or sand which later hardened sufficiently to retain the impressions before the next layer of sediment was deposited. Some fossils can even provide details of how wet the sand was when they were being produced, and hence allow estimation of paleo-wind directions. Assemblages of trace fossils occur at certain water depths, and can also reflect the salinity and turbidity of the water column.
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Amniotes (from Greek ἀμνίον amnion, "membrane surrounding the fetus", earlier "bowl in which the blood of sacrificed animals was caught", from ἀμνός amnos, "lamb"Oxford English Dictionary) are a clade of tetrapod vertebrates comprising the reptiles, birds, and mammals. Amniotes lay their eggs on land or retain the fertilized egg within the mother, and are distinguished from the anamniotes (fishes and amphibians), which typically lay their eggs in water. Older sources, particularly prior to the 20th century, may refer to amniotes as "higher vertebrates" and anamniotes as "lower vertebrates", based on the discredited idea of the evolutionary great chain of being. Amniotes are tetrapods (descendants of four-limbed and backboned animals) that are characterised by having an egg equipped with an amnion, an adaptation to lay eggs on land rather than in water as the anamniotes (including frogs) typically do.
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In 2007, some publications by Lucas and associates at the New Mexico Museum of Natural History and Science came under scrutiny after allegations that information was improperly taken from the unpublished and in- press work of graduate students not on his team. Formal complaints were made to the New Mexico Department of Cultural Affairs regarding publications on a new genus of aetosaur (a type of armored prehistoric reptile from the Triassic), and a reinterpretation of another aetosaur's armor.Nature News, "Fossil reptiles mired in controversy" Published online 30 January 2008 In July 2008, the Ethics Committee of the Society of Vertebrate Paleontology concluded that the matter could not be resolved in favor of either side.SVP news, "Executive committee's Final statement concerning allegations from..." In 2012, he co-authored a paper describing the world's smallest tetrapod footprints, found at Joggins, Nova Scotia.
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No limb remains from Ventastega have been discovered to inform researchers about its locomotion, but paleontologists have been able to infer some basic information about its limbs and locomotion due to its overall morphological similarity to Acanthostega, a limbed tetrapod with digits. While no fossilized trackways from Ventastega have yet been discovered, discoveries of late Devonian trackways from closely related Ichthyostega and Acanthostega along with other early tetrapods indicate that the most stable gait for early tetrapods, including Ventastega, would a lateral-sequence walk. The trackway patterns, including marks from the tetrapods dragging their tails and bellies on the ground, have both been subaerial and subaqueous, indicating that the origin of terrestrial locomotion originated in tetrapods, not in their fish ancestors. Ventastega likely had subaqueous locomotion, which can be inferred from its close relation to Acanthostega, which researchers hypothesized moved subaqueously.
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Related studies demonstrate that metazoan genomes are partitioned in structural and functional units around a megabase long called Topological association domains (TADs) containing dozens of genes regulated by hundreds of enhancers distributed within large genomic regions containing only non-coding sequences. The function of TADs is to regroup enhancers and promoters interacting together within a single large functional domain instead of having them spread in different TADs. However, studies of mouse development point out that two adjacent TADs may regulate the same gene cluster. The most relevant study on limb evolution shows that the TAD at the 5’ of the HoxD gene cluster in tetrapod genomes drives its expression in the distal limb bud embryos, giving rise to the hand, while the one located at 3’ side does it in the proximal limb bud, giving rise to the arm.
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Spathicephalus is an extinct genus of stem tetrapods (early four-limbed vertebrates) that lived during the middle of the Carboniferous Period. The genus includes two species: the type species S. mirus from Scotland, which is known from two mostly complete skulls and other cranial material, and the species S. pereger from Nova Scotia, which is known from a single fragment of the skull table. Based on the S. mirus material, the appearance of Spathicephalus is unlike that of any other early tetrapod, with a flattened, square-shaped skull and jaws lined with hundreds of very small chisel-like teeth. However, Spathicephalus shares several anatomical features with a family of stem tetrapods called Baphetidae, leading most paleontologists who have studied the genus to place it within a larger group called Baphetoidea, often as part of its own monotypic family Spathicephalidae.
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Westlothiana, a small reptile-like tetrapod which may be an early lepospondyl, close to the origin of amniotes, or both Exactly where the border between reptile-like amphibians (non-amniote reptiliomorphs) and amniotes lies will probably never be known, as the reproductive structures involved fossilize poorly, but various small, advanced reptiliomorphs have been suggested as the first true amniotes, including Solenodonsaurus, Casineria and Westlothiana. Such small animals laid small eggs, 1 cm in diameter or less. Small eggs would have a small enough volume to surface ratio to be able to develop on land without the amnion and chorion actively effecting gas exchange, setting the stage for the evolution of true amniotic eggs. Although the first true amniotes probably appeared as early as the Middle Mississippian sub-epoch, non-amniote (or amphibian) reptiliomorph lineages coexisted alongside their amniote descendants for many millions of years.
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To make way for a migration, however, the two tooth-bearing bones of the upper jaw, the maxilla and the premaxilla, would have to separate to let the nostril through and then rejoin; until recently, there was no evidence for a transitional stage, with the two bones disconnected. Such evidence is now available: a small lobe-finned fish called Kenichthys, found in China and dated at around 395 million years old, represents evolution "caught in mid-act", with the maxilla and premaxilla separated and an aperture --the incipient choana--on the lip in between the two bones. Kenichthys is more closely related to tetrapods than is the coelacanth, which has only external nares; it thus represents an intermediate stage in the evolution of the tetrapod condition. The reason for the evolutionary movement of the posterior nostril from the nose to lip, however, is not well understood.
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Jennifer Alice Clack, FRS (née Agnew; 3 November 1947 – 26 March 2020) was an English palaeontologist, an expert in the field of evolutionary biology. She remains one of the preeminent workers known for studying the early evolution of tetrapods, specifically studying the "fish to tetrapod" transition: the origin, evolutionary development and radiation of early tetrapods and their relatives among the lobe-finned fishes. She is best known for her book Gaining Ground: the Origin and Early Evolution of Tetrapods, published in 2002 (second edition, 2012) and written with the layman in mind. Clack was curator at the Museum of Zoology and Professor of Vertebrate Palaeontology at the University of Cambridge, where she devoted her career to studying the early development of tetrapods, the "four-legged" animals said to have evolved from Devonian lobe-finned fishes and colonised the freshwater swamps of the Carboniferous period.
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The bank of the Whiteadder Water in Scotland is one of the few known localities bearing fossils of tetrapods from Romer's gap. The gap in the tetrapod record has been progressively closed with the discoveries of such early Carboniferous tetrapods as Pederpes and Crassigyrinus. There are a few sites where vertebrate fossils have been found to help fill in the gap, such as the East Kirkton Quarry, in Bathgate, Scotland, a long-known fossil site that was revisited by Stanley P. Wood in 1984 and has since been revealing a number of early tetrapods in the mid Carboniferous; "literally dozens of tetrapods came rolling out: Balanerpeton (a temnospondyl), Silvanerpeton and Eldeceeon (basal anthracosaurs), all in multiple copies, and one spectacular proto-amniote, Westlothiana", Paleos Project reports. In 2016, five new species were found across the Ballagan Formation: Perittodus apsconditus, Koilops herma, Ossirarus kierani, Diploradus austiumensis, Aytonerpeton microps.
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Despite the closure of Olson's Gap, the presence of an extinction event at the Kungurian–Roadian boundary was still disputed. It was argued that the observed decrease in diversity might be due to the shift in the location of greatest sample size from the palaeo-equatorial to the palaeo-temperate regions: equatorial regions tend to have a higher diversity in most modern groups. However, a thorough review of the tetrapod-bearing formations during the Kungurian and the Roadian found evidence that the faunal turnover at this time is not a result of the shift in sampling locality; the early Permian temperate faunas are more similar to the early Permian equatorial faunas than the middle Permian temperate faunas. It was also shown that throughout the Permian, the highest diversity was found in temperate regions rather than equatorial regions, and therefore the fall in diversity could not be due to increased sampling of temperate latitudes.
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Thus, the exact timing of the adaptive shift from pelycosaur-grade to therapsid- grade is unclear, but the 7 major therapsid groups (Biarmosuchia, Dinocephalia, Anomodontia, Gorgonopsia, Therocephalia, and Cynodontia) had existed by 265 million years ago. Tetrapod distribution and temperature belts through the Upper Permian and Early Triassic The Permian progressively became dryer and dryer. In the Upper Carboniferous and Lower Permian, pelycosaurs seem to have clung to the everwet coal swamp habitats near the equator (fossils known within 10° of either side of the palaeoequator); beyond this to about 30° was an expansive desert which extended all the way to the coast, separating the swamps from the temperate regions. By the Middle Permian, the equatorial forests had switched to a seasonal wet/dry system, but the swamps were connected to the temperate zones via coastal passages along East Pangaea, allowing cross-continental migration from what is now South Africa to what is now Russia.
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The first observation of biofluorescence in a marine tetrapod Gruber and collaborators reported discoveries of more than 180 new biofluorescent fish species in 2014, as reported in the New York Times's article, "Fluorescence is Widespread in Fish, Study Finds." In 2015, he discovered biofluorescence in Hawksbill sea turtles in the Solomon Islands, marking the first time that scientists had observed biofluorescence in a marine reptile. Field video of this discovery was featured on National Geographic. Also in 2015, Gruber gave a TED Talk on biofluorescence in sea creatures at Mission Blue II which has been viewed over 2.3 million times. In 2020, this discovery was listed by National Geographic as a “top 20 scientific discoveries of the decade” for “Seeing animals’ unexpected sides.” Gruber and collaborators again had video featured on the National Geographic website in 2016 after engineering a "shark-eye" camera, which for the first time allowed scientists to view sharks as they see each other.
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Restoration of Ichthyostega, an early tetrapod from the Devonian Marine otter of the west coast of South America Hawaiian monk seal, off Kaʻula Island This is a list of tetrapods that are semiaquatic; that is, while being at least partly terrestrial, they spend part of their life cycle or a significant fraction of their time in water as part of their normal behavior, and/or obtain a significant fraction of their food from an aquatic habitat. The very earliest tetrapods, such as Ichthyostega, were semiaquatic, having evolved from amphibious lobe-finned fish. Some marine mammals, such as the marine otter, the polar bear and pinnipeds, are semiaquatic, while others, such as the sea otter, cetaceans and sirenians, are fully aquatic. The only fully aquatic nonmarine mammals are several manatees (the Amazonian manatee and some populations of African manatee) and certain small cetaceans (river dolphins, the tucuxi, and some populations of Irrawaddy dolphin and finless porpoise).
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Phreatophasma is an extinct genus of synapsids from the Middle Permian of European Russia. It includes only one species, Phreatophasma aenigmatum, which is itself known from a single femur found in a mine near the town of Belebei in Bashkortostan. Phreatophasma comes from a fossil assemblage that is latest Ufimian to earliest Kazanian in age under the Russian stratigraphic scheme, correlating with the Roadian Age (earliest Middle Permian, about 270 million years ago) under the international stratigraphic timescale. Because the species is based on a single specimen with few diagnostic anatomical features, uncertainty remains as to where it belongs in tetrapod phylogeny; originally interpreted in 1954 as an enigmatic "theromorph" synapsid (hence its species name aenigmatum) by Soviet paleontologist Ivan Yefremov, Phreatophasma was later described as a therapsid incertae sedis by American paleontologist Alfred Romer in 1956 and then as a member of a basal synapsid family called Caseidae starting with Everett C. Olson in 1962.
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Biseridens ("two rows of teeth") is an extinct genus of anomodont therapsid, and one of the most basal anomodont genera known. Originally known from a partial skull misidentified as an 'eotitanosuchian' in 1997, another well- preserved skull was found in the Xidagou Formation, an outcropping in the Qilian Mountains of Gansu, China, in 2009 that clarified its relationships to anomodonts, such as the dicynodonts. Among tetrapod taxa, the therapsid clade anomodontia in which Biseridens belong has one of the largest population sizes, highest levels of diversity, and longest stratigraphic range (Middle Permian to the Triassic, possibly into the Cretaceous), as well as being one of the only clades known from all the continents. Primarily understood from the recently discovered, most-well preserved specimen, Biseridens is most notably distinguishable as an anomodont due to its short snout, dorsally elevated zygomatic arch, and presence of a septomaxilla that distinctly lacks a facial exposure between the nasal and maxilla.
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Given that Doragnathus and Spathicephalus were the only known Carboniferous tetrapods at the time with marginal teeth that are very small and closely packed, Lebedev argued that the two represent the same taxon. Because the Doragnathus material was smaller than every S. mirus specimen that was known at the time, he also proposed that Doragnathus represented the juvenile form of Spathicephalus and that the curved, pointed teeth of the former transformed into the straight, chizel-shaped teeth of the latter during development. However, this hypothesis was refuted by Beaumont and Smithson, who in 1998 reported a jaw of S. mirus that was just as small as the Doragnathus material but possessed straight, chizel-shaped teeth. Beaumont and Smithson also pointed out that Doragnathus differs from Spathicephalus in possessing an additional tooth row along the parasymphesial plate and coronoids (a series of bones forming the inner parts of the lower jaw of early tetrapods that was lost later in tetrapod evolution).
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This paleontological heritage was uncovered also by significant mining works, such as underground mines and open cast mines, such works permitting the three- dimensional studies of the continental deposits, a unique opportunity in Europe and in the world, until the unfortunate closing of the last major mine in 2006. Still, the sterile dumps of the former mines and the former open cast mines of Ponor and Colonia Ceha very are rich in plant material, and they represent the subject of local conservation, as preserved sites or Sites of Special Scientific Interest (SSSI). View from Oravița - Anina mountain railway in 2010 The Early Jurassic (Hettangian - Sinemurian) flora is represented by Bryophytes (Hepaticae), Pteridophytes (Filicopsida, Sphenopsida, Lycopsida) and Gymnosperms (Pteridospermopsida, Ginkgopsida, Cycadopsida, Coniferopsida), with numerous coal generators (Givulescu, 1998, Popa and Van Konijnenburg - Van Cittert, 2005). Very rare vertebrate tunnels were recently described (Popa and Kedzior, 2006), such burrows being formerly reported only from three occurrences in the world (South Africa, Arizona and Argentina), tetrapod tracks such as Batrachopus cf.
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Case began by sorting out some of the taxonomic synonymies and other puzzles created by the "Bone Wars" of the two giants of the heroic age of dinosaur-hunting in the American West, in a series of three monographs dealing with the vertebrates of the Permian or Permo-Carboniferous of North America. Case then turned to his lifelong interest in filling in the fossil record of Permian and Carboniferous vertebrates from the 'Red Beds' of Texas, New Mexico, and Oklahoma. He also made extensive Jurassic collections at Como Bluff, Wyoming, in the Cretaceous deposits in Kansas, and Cenozoic formations of the Green River Basin and the Badlands of South Dakota. Among Case's prolific output several great monographs about Permo-Carboniferous vertebrates stand out: Revision of the Amphibia and Pisces of the Permian of North America (1911)), The Permo-Carboniferous Red Reds of North America and their Vertebrate Fauna (1915), The Environment of Vertebrate Life in the Late Paleozoic in North America, a paleographic study (1919) and Environment of Tetrapod Life in the Late Paleozoic of Regions Other than North America (1926).
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His second discovery of a new amphibian family was in 2012, the Chikilidae, popularly called tailless burrowing caecilians or chikilids, published in the journal Proceedings of the Royal Society, Series B. This discovery was called the 'discovery of the year' and as 'another giant scientific discovery'.Darrel Frost in The Times of India, 22 Feb 2012 Both these discoveries of ancient lineages (both the families about 140 million years old) shed significant light on biogeographic history of the Earth, particularly that of the Gondwana, and in understanding the present-day continental distribution patterns of organisms–while the closest relatives of the purple frog lives 3,000 km across the Indian Ocean in the Seychelles, that of the chikilids is found 7,000 km in Africa. Notable among his new species discoveries are India's first canopy frog Raorchestes nerostgona; India's smallest tetrapod Nyctibatrachus minimus, a frog whose adults do not grow more than 10 mm; and Nasikabatrachus sahyadrensis, the famed purple frog. A critical aspect of Biju's work has been the combination of molecular techniques with traditional approaches bringing on par with the international practice in amphibian research.
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After the collapse of the original bridge on November 7, 1940, PSH 14 was truncated to Gig Harbor and traffic was redirected to a ferry landing in Manchester. The second Tacoma Narrows Bridge was opened on October 14, 1950, and PSH 14 was extended the following year to an intersection with U.S. Route 99 (US 99) in Downtown Tacoma. PSH 14 was replaced by SR 16 under the sign route system created during the 1964 state highway renumbering, traveling from US 99 in Tacoma to SR 3 in Gorst. WSDOT began converting the SR 16 corridor to a controlled-access freeway with the construction of the Nalley Valley Viaduct in 1969, designed with tetrapod columns at a cost of $3.67 million. The viaduct opened on October 29, 1971, and connected SR 16 to I-5 in Tacoma, part of a new freeway replacing Bantz Boulevard between I-5 and the Tacoma Narrows Bridge. A bypass of Purdy on the Pierce-Kitsap county line was opened in 1977 and the former route of SR 16 was divided between SR 302 and its spur route. The remainder of SR 16 in Port Orchard was upgraded to a freeway during the 1980s; however, at-grade intersections remained at Mullenix Road until 1993 and Burley-Olalla Road until 2009.
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