Monday, May 30, 2016

Fossil evidence for Pangaea also include fossils on Antarctica

Fossil evidence for Pangaea includes the presence of similar and identical species on continents that are now great distances apart. For example, fossils of the therapsid Lystrosaurus have been found in South Africa, India and Antarctica, alongside members of the Glossopteris flora, whose distribution would have ranged from the polar circle to the equator if the continents had been in their present position; similarly, the freshwater reptile Mesosaurus has been found in only localized regions of the coasts of Brazil and West Africa.[19]
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Pangaea 

Often when we think of Antarctica we think of only a frozen wastland most or all of the year with the ice and snow there never melting. This is true. But, it is also true that once Antarctica was no under ice and likely because of Global Warming and Global Climate change it will be free of ice eventually again (unless all this triggers another ice age like it often has in the past). However, then it might not be Antarctica that is frozen but other places instead. It sort of depends upon various different factors.

For example therapsid Lystrosaurus are found alongside of Glossopteris Flora.

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 therapsid

Therapsid

From Wikipedia, the free encyclopedia
Therapsids
Temporal range: Early Permian–Holocene 275–0 Ma (Range includes mammals)
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Inostrancevia alexandri.JPG
Mounted skeleton of Inostrancevia alexandri, a gorgonopsian therapsid
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Sphenacodontoidea
Order: Therapsida
Broom, 1905
Clades
Therapsida is a group of synapsids that includes mammals and their ancestors.[1][2] Many of the traits today seen as unique to mammals had their origin within early therapsids, including having their four limbs extend vertically beneath the body, as opposed to the sprawling posture of other reptiles. The earliest fossil attributed to Therapsida is Tetraceratops insignis from the Lower Permian.[3][4] Therapsids evolved from pelycosaurs (specifically sphenacodonts) 275 million years ago. They replaced the pelycosaurs as the dominant large land animals in the Middle Permian and were replaced, in turn, by the archosauromorphs in the Triassic, although one group of therapsids, the kannemeyeriiforms, remained diverse in the Late Triassic. The therapsids included the cynodonts, the group that gave rise to mammals in the Late Triassic around 225 million years ago. Of the non-mammalian therapsids, only cynodonts and dicynodonts survived the Triassic–Jurassic extinction event. The last of the non-mammalian therapsids, the tritylodontid cynodonts, became extinct in the Early Cretaceous, approximately 100 million years ago.

Contents

Characteristics


Illustration of Pristerognathus, a cat-sized therocephalian therapsid
Compared to their pelycosaurian ancestors, early therapsids had very similar skulls but very different post-cranial morphology.

Legs and feet

Therapsids had legs positioned more vertically beneath their bodies than were the sprawling legs of reptiles and pelycosaurs. Also compared to these groups, the feet were more symmetrical, with the first and last toes short and the middle toes long, an indication that the foot's axis was placed parallel to that of the animal, not sprawling out sideways. This orientation would have given a more mammal-like gait than the lizard-like gait of the pelycosaurs.[5]

Jaw and teeth

Therapsids' temporal fenestrae are greater than those of the pelycosaurs. The jaws of some therapsids are more complex and powerful, and the teeth are differentiated into frontal incisors for nipping, great lateral canines for puncturing and tearing, and molars for shearing and chopping food.

Fur and Endorthermy

Several characteritics in therapsids have been noted as being consistent with the development of endothermy: the presence of turbinates, erect limbs, highly vascularised bones, limb and tail proportions conductive to the preservation of body heat and the absence of growth rings in bones.[6] Therefore, like modern mammals, non-mammalian therapsids were most likely warm-blooded.
Recent studies on Permian coprolites showcase that hair was present in at least some therapsids.[7] Hair is by any means present in the docodont Castorocauda, and whiskers are inferred from therocephalians and cynodonts.

Evolutionary history

See also: Evolution of mammals

Raranimus, a primitive therapsid
Therapsids evolved from a group of pelycosaurs called sphenacodonts.[8][9] Therapsids became the dominant land animals in the Middle Permian, displacing the pelycosaurs. Therapsida consists of four major clades: the dinocephalians, the herbivorous anomodonts, the carnivorous biarmosuchians, and the mostly carnivorous theriodonts. After a brief burst of evolutionary diversity, the dinocephalians died out in the later Middle Permian (Guadalupian) but the anomodont dicynodonts as well as the theriodont gorgonopsians and therocephalians flourished, being joined at the very end of the Permian by the first of the cynodonts.
Like all land animals, the therapsids were seriously affected by the Permian–Triassic extinction event; the very successful gorgonopsians dying out altogether and the remaining groups - dicynodonts, therocephalians, and cynodonts - reduced to a handful of species each by the earliest Triassic. The dicynodonts, now represented by a single family of large stocky herbivores, the Kannemeyeridae, and the medium-sized cynodonts (including both carnivorous and herbivorous forms), flourished worldwide throughout the Early and Middle Triassic. They disappear from the fossil record across much of Pangea at the end of the Carnian (Late Triassic), although they continued for some time longer in the wet equatorial band and the south.

Lemurosaurus
Some exceptions were the still further derived eucynodonts. At least three groups of them survived. They all appeared in the Late Triassic period. The extremely mammal-like family, Tritylodontidae, survived into the Early Cretaceous. Another extremely mammal-like family, Tritheledontidae, are unknown later than the Early Jurassic. Mammaliaformes was the third group, including Morganucodon and similar animals. Many taxonomists refer to these animals as "mammals", though some limit the term to the mammalian crown group.
The non-eucynodont cynodonts survived the Permian-Triassic extinction; Thrinaxodon, Galesaurus and Platycraniellus are known from the Early Triassic. By the Middle Triassic, however, only the eucynodonts remained.
The therocephalians, relatives of the cynodonts, managed to survive the Permian-Triassic extinction and continued to diversify through the Early Triassic period. Approaching the end of the period, however, the therocephalians were in decline to eventual extinction, likely outcompeted by the rapidly diversifying Saurian lineage of diapsids, equipped with sophisticated respiratory systems better suited to the very hot, dry and oxygen-poor world of the End-Triassic.
Dicynodonts were long thought to have become extinct near the end of the Triassic, but there is evidence that they survived into the Cretaceous. Their fossils have been found in Gondwana.[10] This is an example of Lazarus taxon. Other animals that were common in the Triassic also took refuge here, such as the temnospondyls.
Mammals are the only living therapsids. The mammalian crown group, which evolved in the Early Jurassic period, radiated from a group of mammaliaforms that included the docodonts. The mammaliaforms themselves evolved from probainognathians, a lineage of the eucynodont suborder.

Taxonomy

Classification


Biarmosuchus, a biarmosuchian

Estemmenosuchus, a dinocephalian

Anteosaurus, an anteosaur

Inostrancevia, a gorgonopsid

Bauria, a therocephalian

Oligokyphus, a cynodont

Phylogeny

Synapsida 

† Caseasauria

 Sphenacodontia 

† Sphenacodontidae

 Therapsida 

† Tetraceratops


 † Biarmosuchia 

† Eotitanosuchidae


† Phthinosuchidae


 Eutherapsida 
 † Dinocephalia 

† Anteosauria


† Tapinocephalia


 Neotherapsida 
 † Anomodontia 

† Dromasauria


† Dicynodontia


 Theriodontia 
 † Gorgonopsia 

† Lycaenops


† Inostrancevia


 Eutheriodontia 
 † Therocephalia 
 † Eutherocephalia 

† Bauria



 Cynodontia 

Mammalia










See also

References



  • Romer, A. S. (1966) [1933]. Vertebrate Paleontology (3rd ed.). University of Chicago Press.

    1. Thulbord, Tony; Turner, Susan (2003). "The last dicynodont: an Australian Cretaceous relict" (PDF). Proceedings of the Royal Society of London B 270: 985–993. doi:10.1098/rspb.2002.2296.

    Further reading

    • Benton, M. J. (2004). Vertebrate Palaeontology, 3rd ed., Blackwell Science.
    • Carroll, R. L. (1988). Vertebrate Paleontology & Evolution. W. H. Freeman & Company, New York.
    • Kemp, T. S. (2005). The origin and evolution of mammals. Oxford University Press.
    • Romer, A. S. (1966). Vertebrate Paleontology. University of Chicago Press, 1933; 3rd ed.
    • Bennett, A. F., & Ruben, J. A. (1986). "The metabolic and thermoregulatory status of therapsids." In The ecology and biology of mammal-like reptiles. Smithsonian Institution Press, Washington, DC, 207-218.

    External links

    Wikispecies has information related to: Therapsida


  • therapsid (fossil reptile order) - Encyclopedia Britannica

  • M. Laurin & R. R. Reisz. 1996. The osteology and relationships of Tetraceratops insignis, the oldest known therapsid. Journal of Vertebrate Paleontology 16(1): 95-102.

  • J. Liu, B. Rubidge & J. Li, New basal synapsid supports Laurasian origin for therapsids, 2009, Acta Palaeontol. Pol., 54 (3): 393-400

  • Carroll, R. L. (1988). Vertebrate Paleontology and Evolution. New York: W. H. Freeman and Company. p. 698. ISBN 0-7167-1822-7.

  • Microbiota and food residues including possible evidence of pre-mammalian hair in Upper Permian coprolites from Russia Piotr Bajdek1, Martin Qvarnström2, Krzysztof Owocki3, Tomasz Sulej3, Andrey G. Sennikov4,5, Valeriy K. Golubev4,5 andGrzegorz Niedźwiedzki2 Article first published online: 25 NOV 2015 DOI: 10.1111/let.12156

  • Microbiota and food residues including possible evidence of pre-mammalian hair in Upper Permian coprolites from Russia Piotr Bajdek1, Martin Qvarnström2, Krzysztof Owocki3, Tomasz Sulej3, Andrey G. Sennikov4,5, Valeriy K. Golubev4,5 andGrzegorz Niedźwiedzki2 Article first published online: 25 NOV 2015 DOI: 10.1111/let.12156

  • Synapsid Classification & Apomorphies

  • A. K. Huttenlocker, and E. Rega, 2012. Chapter 4: The Paleobiology and Bone Microstructure of Pelycosauriangrade Synapsids. Pp. 90–119 in A. Chinsamy (ed. [clarification needed]) Forerunners of Mammals: Radiation, Histology, Biology. Indiana University Press.
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  • Lystrosaurus

  • Lystrosaurus

    From Wikipedia, the free encyclopedia
    Lystrosaurus
    Temporal range: Late Permian–Early Triassic, 255–250 Ma
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    Lystrosaurus hedini.JPG
    Lystrosaurus hedini skeleton at the Museum of Paleontology, Tuebingen
    Scientific classification e
    Kingdom: Animalia
    Phylum: Chordata
    Clade: Synapsida
    Order: Therapsida
    Infraorder: †Dicynodontia
    Family: †Lystrosauridae
    Genus: †Lystrosaurus
    Cope, 1870
    Species
    Lystrosaurus (/ˌlɪstroʊˈsɔːrəs/; "shovel lizard") is a genus of Late Permian and Early Triassic Period dicynodont therapsids, which lived around 250 million years ago in what is now Antarctica, India, and South Africa. Four to six species are currently recognized, although from the 1930s to 1970s the number of species was thought to be much higher. One specimen unearthed in Karoo measured 2.5 meters long.[2][better source needed]
    Being a dicynodont, Lystrosaurus had only two teeth, a pair of tusk-like canines, and is thought to have had a horny beak that was used for biting off pieces of vegetation. Lystrosaurus was a heavily built, herbivorous animal, approximately the size of a pig. The structure of its shoulders and hip joints suggests that Lystrosaurus moved with a semi-sprawling gait. The forelimbs were even more robust than the hindlimbs, and the animal is thought to have been a powerful digger that nested in burrows.
    Lystrosaurus was by far the most common terrestrial vertebrate of the Early Triassic, accounting for as many as 95% of the total individuals in some fossil beds.[3] It has often been suggested that it had anatomical features that enabled it to adapt better than most animals to the atmospheric conditions that were created by the Permian–Triassic extinction event and which persisted through the Early Triassic—low concentrations of oxygen and high concentrations of carbon dioxide.[citation needed] However, recent research suggests that these features were no more pronounced in Lystrosaurus than in genera that perished in the extinction or in genera that survived but were much less abundant than Lystrosaurus.[citation needed]

    Contents

    Description


    Size of Lystrosaurus murrayi relative to a human.
    Lystrosaurus was a dicynodont therapsid, between 0.6 to 2.5 m (2.0 to 8.2 ft) long with an average of about 0.9 m (3.0 ft) depending upon the species.[4]
    Unlike other therapsids, dicynodonts had very short snouts and no teeth except for the tusk-like upper canines. Dicynodonts are generally thought to have had horny beaks like those of turtles, for shearing off pieces of vegetation which were then ground on a horny secondary palate when the mouth was closed. The jaw joint was weak and moved backwards and forwards with a shearing action, instead of the more common sideways or up and down movements. It is thought that the jaw muscles were attached unusually far forward on the skull and took up a lot of space on the top and back of the skull. As a result, the eyes were set high and well forward on the skull, and the face was short.[5]
    Features of the skeleton indicate that Lystrosaurus moved with a semi-sprawling gait. The lower rear corner of the scapula (shoulder blade) was strongly ossified (built of strong bone), which suggests that movement of the scapula contributed to the stride length of the forelimbs and reduced the sideways flexing of the body.[6] The five sacral vertebrae were massive but not fused to each other and to the pelvis, making the back more rigid and reducing sideways flexing while the animal was walking. Therapsids with fewer than five sacral vertebrae are thought to have had sprawling limbs, like those of modern lizards.[6] In dinosaurs and mammals, which have erect limbs, the sacral vertebrae are fused to each other and to the pelvis.[7] A buttress above each acetabulum (hip socket) is thought to have prevented dislocation of the femur (thigh bone) while Lystrosaurus was walking with a semi-sprawling gait.[6] The forelimbs of Lystrosaurus were massive,[6] and Lystrosaurus is thought to have been a powerful burrower.[8]

    Distribution and species

    Lystrosaurus fossils have been found in many Late Permian and Early Triassic terrestrial bone beds, most abundantly in Africa, and to a lesser extent in parts of what are now India, China, Mongolia, European Russia, and Antarctica (which was not over the South Pole at the time).[6]

    Species found in Africa


    Lystrosaurus murrayi
    Most Lystrosaurus fossils have been found in the Balfour and Katberg Formations of the Karoo basin in South Africa; these specimens offer the best prospects of identifying species because they are the most numerous and have been studied for the longest time. As so often with fossils, there is debate in the paleontological community as to exactly how many species have been found in the Karoo.[8] Studies from the 1930s to 1970s suggested a large number (23 in one case).[8] However, by the 1980s and 1990s, only six species were recognized in the Karoo: L. curvatus, L. platyceps, L. oviceps, L. maccaigi, L. murrayi, and L. declivis. A study in 2011 reduced that number to four, treating the fossils previously labeled as L. platyceps and L. oviceps as members of L. curvatus.[9]
    L. maccaigi is the largest and apparently most specialized species, while L. curvatus was the least specialized. A Lystrosaurus-like fossil, Kwazulusaurus shakai, has also been found in South Africa. Although not assigned to the same genus, K. shakai is very similar to L. curvatus. Some paleontologists have therefore proposed that K. shakai was possibly an ancestor of or closely related to the ancestors of L. curvatus, while L. maccaigi arose from a different lineage.[8] L. maccaigi is found only in sediments from the Permian period, and apparently did not survive the Permian–Triassic extinction event. Its specialized features and sudden appearance in the fossil record without an obvious ancestor may indicate that it immigrated into the Karoo from an area in which Late Permian sediments have not been found.[8]
    L. curvatus is found in a relatively narrow band of sediments from shortly before and after the extinction, and can be used as an approximate marker for the boundary between the Permian and Triassic periods. A skull identified as L. curvatus has been found in late Permian sediments from Zambia. For many years it had been thought that there were no Permian specimens of L. curvatus in the Karoo, which led to suggestions that L. curvatus immigrated from Zambia into the Karoo. However, a re-examination of Permian specimens in the Karoo has identified some as L. curvatus, and there is no need to assume immigration.[8]
    L. murrayi and L. declivis are found only in Triassic sediments.[8]
    A pink/grey four-footed animal. The head is facing slightly toward you, and has two big teeth. It is covered in fur and has sharp claws.
    Lystrosaurus georgi

    Other species

    Lystrosaurus georgi fossils have been found in the Earliest Triassic sediments of the Moscow Basin in Russia. It was probably closely related to the African Lystrosaurus curvatus,[6] which is regarded as one of the least specialized species and has been found in very Late Permian and very Early Triassic sediments.[8]

    History

    Map showing where in the world fossils of this animal were found. It indicates that the animal's range extended to South Africa, India, and Antarctica. Other animals include a land reptile, swimming reptile, and a plant, and show that the continents were all joined together once.
    Geographical distribution of Lystrosaurus (    ) and contemporary fossils in Gondwana.
    Dr. Elias Root Beadle, a Philadelphia missionary and avid fossil collector, discovered the first Lystrosaurus skull. Beadle wrote to the eminent paleontologist Othniel Charles Marsh, but received no reply. Marsh's rival, Edward Drinker Cope, was very interested in seeing the find, and described and named Lystrosaurus in the Proceedings of the American Philosophical Society in 1870.[10] Its name is derived from the Ancient Greek words listron "shovel" and sauros "lizard".[11] Marsh belatedly purchased the skull in May 1871, although his interest in an already-described specimen was unclear; he may have wanted to carefully scrutinize Cope's description and illustration.[10]

    Plate tectonics

    The discovery of Lystrosaurus fossils at Coalsack Bluff in the Transantarctic Mountains by Edwin H. Colbert and his team in 1969–70 helped confirm the theory of plate tectonics and convince the last of the doubters, since Lystrosaurus had already been found in the lower Triassic of southern Africa as well as in India and China.[12]

    Paleoecology

    Dominance of the Early Triassic

    Lystrosaurus is notable for dominating southern Pangaea during the Early Triassic for millions of years. At least one unidentified species of this genus survived the end-Permian mass extinction and, in the absence of predators and of herbivorous competitors, went on to thrive and re-radiate into a number of species within the genus,[13] becoming the most common group of terrestrial vertebrates during the Early Triassic; for a while 95% of land vertebrates were Lystrosaurus.[13][14] This is the only time that a single species or genus of land animal dominated the Earth to such a degree.[15] A few other Permian therapsid genera also survived the mass extinction and appear in Triassic rocks—the therocephalians Tetracynodon, Moschorhinus and Ictidosuchoides—but do not appear to have been abundant in the Triassic;[8] complete ecological recovery took 30 million years, spanning the Early and Middle Triassic.[16]
    Several attempts have been made to explain why Lystrosaurus survived the Permian–Triassic extinction event, the "mother of all mass extinctions",[17] and why it dominated Early Triassic fauna to such an unprecedented extent:
    A yellow four-footed animal. Its mouth is closed but contains a horny beak and tusks protruding. It is colored light green/dark yellow and is walking with its legs spread apart.
    Lystrosaurus murrayi
    • One of the more recent theories is that the Permian–Triassic extinction event reduced the atmosphere's oxygen content and increased its carbon dioxide content, so that many terrestrial species died out because they found breathing too difficult.[14] It has therefore been suggested that Lystrosaurus survived and became dominant because its burrowing life-style made it able to cope with an atmosphere of "stale air", and that specific features of its anatomy were part of this adaptation: a barrel chest that accommodated large lungs, short internal nostrils that facilitated rapid breathing, and high neural spines (projections on the dorsal side of the vertebrae) that gave greater leverage to the muscles that expanded and contracted its chest. However, there are weaknesses in all these points: the chest of Lystrosaurus was not significantly larger in proportion to its size than in other dicynodonts that became extinct; although Triassic dicynodonts appear to have had longer neural spines than their Permian counterparts, this feature may be related to posture, locomotion or even body size rather than respiratory efficiency; L. murrayi and L. declivis are much more abundant than other Early Triassic burrowers such as Procolophon or Thrinaxodon.[8]
    Full body view of the skeleton of a four footed animal.
    Lystrosaurus skeletal diagram
    • The suggestion that Lystrosaurus was helped to survive and dominate by being semi-aquatic has a similar weakness: although amphibians become more abundant in the Karoo's Triassic sediments, they were much less numerous than L. murrayi and L. declivis.[8]
    • The most specialized and the largest animals are at higher risk in mass extinctions; this may explain why the unspecialized L. curvatus survived while the larger and more specialized L. maccaigi perished along with all the other large Permian herbivores and carnivores.[8] Although Lystrosaurus generally looks adapted to feed on plants similar to Dicroidium, which dominated the Early Triassic, the larger size of L. maccaigi may have forced it to rely on the larger members of the Glossopteris flora, which did not survive the end-Permian extinction.[8]
    • Only the 1.5 metres (4.9 ft)–long therocephalian Moschorhinus and the large archosauriform Proterosuchus appear large enough to have preyed on the Triassic Lystrosaurus species, and this shortage of predators may have been responsible for a Lystrosaurus population boom in the Early Triassic.[8]
    • Perhaps the survival of Lystrosaurus was simply a matter of luck.[13]

    In popular culture

    A fossil skeleton on display at a museum. It is brown in color and the eye socket is facing right.
    Fossil specimen, Staatliches Museum für Naturkunde Stuttgart
    • BBC 2002 documentary The Day The Earth Nearly Died, a program which discuss the Permian extinction. In the program, the narrator says that Lystrosaurus was the only therapsid to survive the extinction, and that it was the ancestor to all mammals, even humans. This is not correct, as paleontologists do not regard dicynodonta as ancestral to mammals.
    • Impossible Pictures production Walking with Monsters. Here, it was shown evolving from the little dicynodont Diictodon, even though both species lived at the same time though this may be a Triassic species of Lystrosaurus as most species died out in the Permian extinction. The program shows evolution of other creatures of the same time period.
    • Animal Armageddon, 5th episode, "explaining" that the different Lystrosaurus species had interbred with each other to adapt better and to survive during the transition from Permian to Triassic.
    • Lystrosaurus appeared in the Rite of Spring segment in the 1940 animated film Fantasia, where it is shown to dig out clams along with the Plateosaurus and it was one of the animals led by the Stegosaurus.
    • Lystrosaurus was added to the dinosaur sandbox survival video game ARK: Survival Evolved in PC patch v240 on May 4, 2016.

    See also

    Portal icon Paleontology portal

    References


  • "Fossilworks: Lystrosaurus". Paleodatabase.org. Retrieved 2015-08-20.

    1. Erwin DH (1993). The great Paleozoic crisis; Life and death in the Permian. Columbia University Press. ISBN 0-231-07467-0.

    External links



  • [1]

  • Damiani, R. J.; Neveling, J.; Modesto, S.P.; Yates, A.M. (2004). "Barendskraal, a diverse amniote locality from the Lystrosaurus assemblage zone, Early Triassic of South Africa". Palaeontologia Africana 39: 53–62.

  • "Lystrosaurus". Prehistoric Wildlife. Retrieved 8 March 2015.

  • Cowen, R. (2000). The History of Life (3rd ed.). Blackwell Scientific. pp. 167–68. ISBN 0-632-04444-6.

  • Surkov, M.V., Kalandadze, N.N., and Benton, M.J. (June 2005). "Lystrosaurus georgi, a dicynodont from the Lower Triassic of Russia" (PDF). Journal of Vertebrate Paleontology 25 (2): 402–413. doi:10.1671/0272-4634(2005)025[0402:LGADFT]2.0.CO;2. ISSN 0272-4634.

  • Benton, Michael J. (2004). "Origin and relationships of Dinosauria". In Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 7–19. ISBN 0-520-24209-2.

  • Botha, J., and Smith, R.M.H. (2005). "Lystrosaurus species composition across the Permo–Triassic boundary in the Karoo Basin of South Africa". Lethaia 40 (2): 125–137. doi:10.1111/j.1502-3931.2007.00011.x. Full version online at "Lystrosaurus species composition across the Permo–Triassic boundary in the Karoo Basin of South Africa" (PDF). Retrieved 2008-07-02.

  • Grine, F.E., Forster, C.A., Cluver, M.A. & Georgi, J.A. (2006). "Amniote paleobiology. Perspectives on the Evolution of Mammals, Birds, and Reptiles". University of Chicago Press: 432–503.

  • Wallace, David Rains (2000). The Bonehunters' Revenge: Dinosaurs, Greed, and the Greatest Scientific Feud of the Gilded Age. Houghton Mifflin Harcourt. pp. 44–45. ISBN 0-618-08240-9.

  • Liddell, Henry George and Robert Scott (1980). A Greek-English Lexicon (Abridged Edition). United Kingdom: Oxford University Press. ISBN 0-19-910207-4.

  • Naomi Lubick, Investigating the Antarctic, Geotimes, 2005.

  • Michael J. Benton (2006). When Life Nearly Died. The Greatest Mass Extinction of All Time. London: Thames & Hudson. ISBN 0-500-28573-X.

  • [2] Archived October 12, 2007, at the Wayback Machine.

  • BBC: Life Before Dinosaurs

  • Sahney, S. and Benton, M.J. (2008). "Recovery from the most profound mass extinction of all time" (PDF). Proceedings of the Royal Society: Biological 275 (1636): 759–65. doi:10.1098/rspb.2007.1370. PMC 2596898. PMID 18198148.

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    Glossopteris  Flora (in Antarctica)


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    Glossopteris

    From Wikipedia, the free encyclopedia
    Glossopteris
    Temporal range: Permian
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    Glossopteris sp., seed ferns, Permian - Triassic - Houston Museum of Natural Science - DSC01765.JPG
    Glossopteris sp.
    Scientific classification
    Kingdom: Plantae
    Division: †Pteridospermatophyta
    Order: †Glossopteridales
    Family: †Glossopteridaceae
    Genus: †Glossopteris
    Species
    • G. angustifolia
    • G. brasiliensis
    • G. browniana
    • G. communis
    • G. indica
    • G. occidentalis
    Pangaea Glossopteris.jpg
    Fossils of the gymnosperm Glossopteris (dark green) found in all of the southern continents provide strong evidence that the continents were once amalgamated into a supercontinent Gondwana
    Glossopteris (Ancient Greek: γλώσσα glossa, meaning "tongue", because the leaves were tongue-shaped) is the largest and best-known genus of the extinct order of seed ferns known as Glossopteridales (also known as Arberiales or Ottokariales). The genus Glossopteris refers only to leaves, within a framework of form genera used in paleobotany. For likely reproductive organs see Glossopteridaceae, and these are important because they indicate biological identity of these plants that were critical for recognizing former connections between the varied fragments of Gondwana: South America, Africa, India, Australia, New Zealand, and Antarctica.

    Contents

    History

    The Glossopteridales arose in the Southern Hemisphere around the beginning of the Permian Period (298.9 million years ago).[1] Their distribution across several, now detached, landmasses led Eduard Suess, amongst others, to propose that the southern continents were once amalgamated into a single supercontinent—Pangea.[2] These plants went on to become the dominant elements of the southern flora through the rest of the Permian but disappeared in almost all places at the end of the Permian (252.17 million years ago).[3][4][5] The only convincing Triassic records are very earliest Triassic leaves from Nidpur, India,[6] but even these records are somewhat questionable owing to faulting and complex juxtapositioning of Permian and Triassic strata at Nidpur. Although most modern palaeobotany textbooks cite the continuation of glossopterids into later parts of the Triassic and, in some cases into the Jurassic, these ranges are erroneous and are based on misidentification of morphologically similar leaves such as Gontriglossa,[7] Sagenopteris, or Mexiglossa.[8] Glossopterids were, thus, one of the major casualties of the end-Permian mass extinction event.[9]
    Location of Glossopteris remains shown in green in the former Supercontinent Gondwana.
    More than 70 fossil species of this genus have been recognized in India alone,[10] with additional species from South America, Australia,[11][12] Africa, Madagascar[13] and Antarctica.[14] Essentially, Glossopteris was restricted to the middle- and high-latitude parts of Gondwana during the Permian [15] and was an important contributor to the vast Permian coal deposits of the Southern Hemisphere continents.[16] Most northern parts of South America and Africa lack Glossopteris and its associated organs. However, in recent years a few disparate localities in Morocco, Oman, Anatolia, the western part of the island of New Guinea, Thailand and Laos have yielded fossils that are of possible glossopterid affinity.[17] These peri-gondwanan records commonly occur together with Cathaysian or Euramerican plant species—the assemblages representing a zone of mixing between the strongly provincial floras of the Permian.[18] Apart from those in India and the peri-gondwanan localities, a few other fossils from the Northern Hemisphere have been assigned to this group, but these are not identified with great certainty. For example, specimens assigned to Glossopteris from the far east of Russia in the 1960s are more likely to be misdentifications of other gymnosperms such as Pursongia.[19] Confident assignment of fossil leaves to Glossopteris normally requires their co-preservation with the distinctive segmented roots of this group (called Vertebraria) or with the distinctive fertile organs.[20]

    Taxonomy

    Long considered a fern after its discovery in the 1820s,[21] it was later assigned to the gymnosperms. The genus is placed in the division Pteridospermatophyta. In reality, many of the plant groups included within this division are only distantly related to one another. Glossopterids' relationships with other groups remain obscure. Most recent phylogenetic analyses favour placement of glossopterids as sister to a large group including Corystospermales, Caytoniales, Bennettitales, Pentoxylales, Gnetales (in some analyses), and angiosperms.[22] A few analyses favour alternative links with Ginkgoales, Cordaitales and Pinales.
    Glossopteris should strictly be used to refer to the distinctive spathulate fossil leaves with reticulate venation, however, the term has also been used to refer to the parent plant as a whole.[23]

    Description

    Glossopteris browniana fossil in the Artis zoo, Amsterdam.
    Glossopteris was a woody, seed-bearing shrub or tree, some apparently reaching 30 metres (98 ft) tall. They had a softwood interior that resembles conifers of the family Araucariaceae.[24] Seeds were borne on one side of variably branched or fused structures,[25][26][27][28][29][30] and microsporangia containing pollen were borne in clusters at the tips of slender filaments.[31] Both the seed- and pollen-bearing organs were partially fused (adnate) to the leaves, or, in some cases, possibly positioned in the axils of leaves. The homologies of the flattened seed-bearing structures have remained particularly controversial with some arguing that the fertile organs represent megasporophylls (fertile leaves) whereas others have interpreted the structures as flattened, seed-bearing, axillary axes (cladodes). It is unclear whether glossopterids were monoecious or dioecious.

    Paleoecology

    They are interpreted to have grown in very wet soil conditions,[32][33] similar to the modern Bald Cypress. The leaves ranged from about 2 cm to over 30 cm in length.
    The profile of glossopterid trees is largely speculative as complete trees have not been preserved. However, based on analogies with modern high-latitude plants Glossopteris trees probably tapered upwards like a Christmas tree and were relatively widely spaced to take advantage of the low-angle sunlight at high latitudes. Instead of needles, they had large, broad lance- or tongue-shaped leaves that fell to the ground at the end of summer. The fossil leaves are commonly found as dense accumulations representing autumnal leaf banks.[34][35] The broad fossilized growth rings in many Glossopteris woods reveal that the plants experienced strong growth spurts each spring-summer but underwent abrupt cessation of growth before each following winter.[36]
    Glossopteris leaves are morphologically simple so there are few characters that can be used to differentiate species.[37] Consequently, many past researchers have considered the Permian Glossopteris flora to be rather homogeneous with the same species distributed throughout the Southern Hemisphere. However, more recent studies of the more morphologically diverse fertile organs have shown that taxa had more restricted regional distributions and several intra-gondwanan floristic provinces are recognizable. Seeds, much too large to be wind-borne, could not have blown across thousands of miles of open sea, nor is it likely they have floated across vast oceans. Observations such as these led the Austrian geologist Eduard Suess to deduce that there had once been a land bridge between these areas. He named this large land mass Gondwanaland (named after the district in India where the plant Glossopteris was found). These same observations would also lend support to Alfred Wegener's Continental drift theory.
    The first Antarctic specimens of Glossopteris were discovered by members of Robert Scott's doomed Terra Nova Expedition. The expedition members abandoned much of their gear in an effort to reduce their load, but kept 35 pounds of Glossopteris fossils; these were found alongside their bodies.[38]

    Outcrops in Brazil

    The first investigation of a Glossopteris flora associated with coal seams within a paleogeographic and palaeoclimatic context, in the Paraná Basin, southern Brazil, was that by geologist Israel Charles White in 1908. This allowed correlation between Gondwanan coal deposits in southern Brazil and those documented in South Africa, Australia, India and Antarctica, and showed that this flora flourished in latitudes near the south pole.
    In Rio Grande do Sul, Glossopteris leaves were found in paleorrota at Mina Faxinal, in Arroio dos Ratos at Mina Morro do Papaléo in Mariana Pimentel and Quitéria in Pantano Grande. Various species were recovered from the Rio Bonito Formation at these sites including G. angustifolia, G. brasiliensis, G. browniana, G. communis, G. indica and G. occidentalis.[39]

    References


  • McLoughlin, S., 2012. Glossopteris – insights into the architecture and relationships of an iconic Permian Gondwanan plant. Journal of the Botanical Society of Bengal 65(2), 1–14.
    1. Adami-Rodrigues, Karen; Alves de Souza, Paulo; Iannuzzi, Roberto; Pinto, Irajá Damiani (2004). "Herbivoria em Floras Gonduânicas do NeoPaleózoico do Rio Grande do Sul" (PDF). Revista Brasileira de Paleontologia 7 (2): 93–102.

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    • Anderson, H.M. & Anderson, J.M. 1985. The Palaeoflora of Southern Africa: Prodromus of Southern African Megafloras, Devonian to Lower Cretaceous. A.A. Balkema, Rotterdam. 416 pp.
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    • Davis, Paul and Kenrick, Paul. 2004. Fossil Plants. Smithsonian Books (in association with the Natural History Museum of London), Washington, D.C. ISBN 1-58834-156-9
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    • Pant, D.D. & Gupta, K.L. 1971. Cuticular structure of some Indian Lower Gondwana species of Glossopteris Brongniart. Part 2. - Palaeontographica, 132B: 130-152.
    • Pant, D.D. & Nautiyal, D.D. 1987. Diphyllopteris verticellata Srivastava, the probable seedling of Glossopteris from the Paleozoic of India. - Rev. Palaeobot. Palynol., 51: 31-36.
    • Pant, D.D. & Pant, R. 1987. Some Glossopteris leaves from Indian Triassic beds. - Palaeontographica, 205B: 165-178.
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    • Pigg, K.B. & McLoughlin, S. 1997. Anatomically preserved Glossopteris leaves from the Bowen and Sydney basins, Australia. Review of Palaeobotany and Palynology, 97: 339-359.
    • Plumstead, E.P. (1969), Three thousand million years of plant life in Africa. Alex L. du Toit Memorial Lecture no. 11. Trans. Geol. Soc. S. Afr. 72 (annex.): 1-72.
    • Taylor, E.L, Taylor, T.N. & Collinson, J.W. 1989. Depositional setting and palaeobotany of Permian and Triassic permineralized peat from the central Transantarctic Mountains, Antarctica. - Internat. J. Coal Geol., 12: 657-679.

    External links

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  • McLoughlin, S. 2001. "The breakup history of Gondwana and its impact on pre-Cenozoic floristic provincialism". Australian Journal of Botany, 49: 271-300.
  • McLoughlin, S., Lindström, S. & Drinnan, A.N. 1997 "Gondwanan floristic and sedimentological trends during the Permian-Triassic transition: new evidence from the Amery Group, northern Prince Charles Mountains, East Antarctica". Antarctic Science, 9: 281-298.
  • Vajda, V. & McLoughlin, S. 2007. "Extinction and recovery patterns of the vegetation across the Cretaceous–Palaeogene boundary — a tool for unravelling the causes of the end-Permian mass-extinction". Review of Palaeobotany and Palynology 144: 99–112.
  • Lindström, S. & McLoughlin, S. 2007. "Synchronous palynofloristic extinction and recovery after the end- Permian event in the Prince Charles Mountains, Antarctica: implications for palynofloristic turnover across Gondwana". Review of Palaeobotany and Palynology 145: 89-122.
  • Pant, D.D. & Pant, R., 1987. Some Glossopteris leaves from Indian Triassic beds. Palaeontographica 205B, 165-178.
  • Anderson, J. M. & Anderson, H. M., 1985. "Palaeoflora of southern Africa. Prodomus of southern African megafloras Devonian to Lower Cretaceous". A.A. Balkema, Rotterdam. 423 pp.
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  • McLoughlin, S., Lindström, S. & Drinnan, A.N. 1997. "Gondwanan floristic and sedimentological trends during the Permian-Triassic transition: new evidence from the Amery Group, northern Prince Charles Mountains, East Antarctica". Antarctic Science, 9: 281-298.
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