Tetrapoda

Reconstruction of the 2m long Early Carboniferous Crassigyrinus scoticus from here.


Belongs within: Sarcopterygii.
Contains: Temnospondyli, Reptiliomorpha.

Tetrapoda is the clade of vertebrates in which legs rather than fins became the main motile organs, containing modern reptiles, amphibians, birds and mammals. As used herein, Tetrapoda is defined by the presence of limbs with separate terminal digits. The earliest known tetrapods come from the late Frasnian (early Late Devonian). These early forms were still aquatic; tetrapods did not become terrestrial until later. The best known of these basal aquatic tetrapods are Acanthostega and Ichthyostega, but even more basal forms are known such as Ventastega that retain 'fish-like' characters such as coronoid fangs in the jaw that are absent in the former two taxa (Ahlberg et al. 2008).

See also: Some history of the history of tetrapods.

Synapomorphies (from Ahlberg et al. 2008): Supracleithrum and post-temporal absent; scapulocoracoid enlarged; coracoid foramen absent; interclavicle enlarged; sacrum present.

<==Tetrapoda [Eutetrapoda, Labyrinthodontia, Stegocephali]
    |--+--Elginerpeton pancheni Ahlberg 1995 AC08, RCQ03
    |  `--Obruchevichthys gracilis Vorobyeva 1977 RCQ03
    `--+--Densignathus rowei Daeschler 2000 AC08, RCQ03
       `--+--Ventastega curonica Ahlberg, Luksevics & Lebedev 1994 AC08, RCQ03
          `--+--Metaxygnathus denticulus Campbell & Bell 1977 AC08, RCQ03
             `--+--Acanthostega [Acanthostegidae] AC08
                |    `--A. gunnari Jarvik 1952 RCQ03
                `--+--Ichthyostega [Ichthyostegalia, Ichthyostegidae] AC08
                   |    `--I. stensioei Säve-Söderbergh 1932 RCQ03
                   `--+--Tulerpeton curtum Lebedev 1984 RCQ03
                      `--Whatcheeriidae C02
                           |--Whatcheeria deltae Lombard & Bolt 1995 AC08, RCQ03
                           `--+--Pederpes Clack 2002 AC08, C02
                              |    `--*P. finneyae Clack 2002 C02
                              `--+--Colosteidae RCQ03
                                 |    |--Colosteus scutellatus (Newberry 1856) RCQ03
                                 |    |--Greererpeton burkemorani Romer 1969 AC08, RCQ03
                                 |    `--Pholidogaster pisciformis PS88, S85
                                 `--+--Crassigyrinus Panchen 1980 AC08, S85 [Crassigyrinidae, Palaeostegalia]
                                    |    `--C. scoticus Watson 1929 RCQ03 [=Macromerium scoticum S85]
                                    `--Neostegalia [Amphibia, Lissamphibia, Procera] S85
                                         |  i. s.: Bothriceps F71
                                         |           |--B. australis Huxley 1859 F71
                                         |           `--B. major Woodward 1909 F71
                                         |         Subcyclotosaurus brookvalensis Watson 1958 F71
                                         |--Baphetidae [Loxommatidae, Loxommatoidea] RCQ03
                                         |    |--Spathicephalus Watson 1929 RCQ03
                                         |    `--+--Megalocephalus pachycephalus (Barkas 1873) RCQ03
                                         |       |--Baphetes kirkbyi Watson 1929 AC08, RCQ03
                                         |       `--Loxomma Huxley 1862 RCQ03
                                         |            `--L. acutirhinus PS88
                                         `--Neotetrapoda [Gradientia, Neobatrachii] RCQ03
                                              |--Batrachomorpha [Paratoidea] PS88
                                              |    |--Eucritta melanolimnetes Clack 1998 RCQ03
                                              |    `--Temnospondyli RCQ03
                                              `--+--Caerorhachis bairdi Holmes & Carroll 1977 RCQ03
                                                 `--Reptiliomorpha AC08

Tetrapoda incertae sedis:
  Sinostega Zhu & Ahlberg in Zhu, Ahlberg et al. 2002 ZA02
    `--*S. pani Zhu & Ahlberg in Zhu, Ahlberg et al. 2002 ZA02
  Hynerpeton bassetti Daeschler, Shubin et al. 1994 RCQ03
  Manchurochelys ZBH03
    |--M. liaoxiensis ZBH03
    `--M. manchuensis ZBH03
  Monjurosuchus splendens ZBH03
  Yabeinosaurus tenuis ZBH03
  Hyphalosaurus lingyuanensis ZBH03
  Liaobatrachus grabaui ZBH03
  Callobatrachus sanyanensis ZBH03
  Mesophyne beipiaoensis ZBH03
  Livoniana multidentata Ahlberg, Lukseviks & Mark-Kurik 2000 RCQ03
  Labyrinthodon W70
    |--L. jaegeri W70
    `--L. leptognathus W70
  Diadetognathus varvicensis W70
  Doragnathus S85
  Papposaurus traquairi S85
  Cyrtopodion LK03
    |--C. heterocercus LK03
    `--C. kotschyi LK03
  Laudakia stellio LK03
  Mesalina brevirostris LK03
  Ophisops elegans LK03
    |--O. e. elegans LK03
    |--O. e. blanfordi LK03
    `--O. e. ehrenbergi LK03
  Ophiomorus latastii LK03
  Eirenis LK03
    |--E. modestus LK03
    `--E. rothi LK03
  Rhynchocalamus melanocephalus LK03

*Type species of generic name indicated

REFERENCES

[AC08] Ahlberg, P. E., J. A. Clack, E. Lukševičs, H. Blom & I. Zupiņš. 2008. Ventastega curonica and the origin of tetrapod morphology. Nature 453: 1199-1204.

[C02] Clack, J. A. 2002. An early tetrapod from ‘Romer’s Gap’. Nature 418: 72-76.

[F71] Fletcher, H. O. 1971. Catalogue of type specimens of fossils in the Australian Museum, Sydney. Australian Museum Memoir 13: 1-167.

[LK03] Lymberakis, P. & A. Kalionzopoulou. 2003. Additions to the herpetofauna of Syria. Zoology in the Middle East 29: 33-39.

[PS88] Panchen, A. L., & T. R. Smithson. 1988. The relationships of the earliest tetrapods. In The Phylogeny and Classification of the Tetrapods, vol. 1. Amphibians, Reptiles, Birds (M. J. Benton, ed.) pp. 1-32. Clarendon Press: Oxford.

[RCQ03] Ruta, M., M. I. Coates & D. L. J. Quicke. 2003. Early tetrapod relationships revisited. Biological Reviews 78: 251-345.

[S85] Smithson, T. R. 1985. The morphology and relationships of the Carboniferous amphibian Eoherpeton watsoni Panchen. Zoological Journal of the Linnean Society 85: 317-410.

[W70] Wills, L. J. 1970. The Triassic succession in the central Midlands in its regional setting. Quarterly Journal of the Geological Society of London 126: 225-283.

[ZBH03] Zhou, Z., P. M. Barrett & J. Hilton. 2003. An exceptionally preserved Lower Cretaceous ecosystem. Nature 421: 807-814.

[ZA02] Zhu, M., P. E. Ahlberg, W. Zhao & L. Jia. 2002. First Devonian tetrapod from Asia. Nature 420: 760-761.

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