Tetrapoda

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


Belongs within: Sarcopterygii.
Contains: Aistopoda, Neostegalia.

The Tetrapoda are 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). Acanthostega and Ichthyostega are known to have had limbs with more digits than typically found in crown-group tetrapods: eight in Acanthostega and seven in Ichthyostega.

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
             |--Ymeria denticulata PS17
             `--+--Ichthyostega Säve-Söderbergh 1932 PS17, D07 [Ichthyostegalia, Ichthyostegidae]
                |    |--I. eigili D07
                |    |--I. kochi D07
                |    |--I. stensioei Säve-Söderbergh 1932 RCQ03
                |    `--I. watsoni D07
                `--+--Acanthostega Jarvik 1952 PS17, D07 [Acanthostegidae]
                   |    `--A. gunnari Jarvik 1952 RCQ03
                   `--+--Tulerpeton curtum Lebedev 1984 RCQ03
                      |--Aistopoda PS17
                      `--+--Whatcheeriidae C02
                         |    |--Whatcheeria deltae Lombard & Bolt 1995 PS17, RCQ03
                         |    `--Pederpes Clack 2002 PS17, C02
                         |         `--*P. finneyae Clack 2002 C02
                         `--+--Crassigyrinus Panchen 1980 PS17, S85 [Crassigyrinidae, Palaeostegalia]
                            |    `--C. scoticus Watson 1929 RCQ03 [=Macromerium scoticum S85]
                            `--+--Colosteidae RCQ03
                               |    |--Colosteus scutellatus (Newberry 1856) RCQ03
                               |    |--Greererpeton Romer 1969 PS17, D07
                               |    |    `--G. burkemorani Romer 1969 RCQ03
                               |    `--Pholidogaster Huxley 1862 PS88, D07
                               |         `--P. pisciformis [incl. Otocratia modesta] G88
                               `--Neostegalia PS17

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
  Yabeinosaurus tenuis 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
  Platyceps Stephens 1887 S87
    `--*P. wilkinsonii Stephens 1887 S87
  Gondwanosaurus bijoriensis S87
  Ruhuhuaria reiszi NB17
  Stanocephalosaurus pronus NB17
  Mandagomphodon NB17
    |--M. attridgei NB17
    `--M. hirschsoni NB17
  Stenaulorhynchus stockleyi NB17
  Cricodon metabolus NB17

*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.

[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.

[G88] Gray, J. 1988. Evolution of the freshwater ecosystem: the fossil record. Palaeogeography, Palaeoclimatology, Palaeoecology 62: 1–214.

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

[NB17] Nesbitt, S. J., R. J. Butler, M. D. Ezcurra, P. M. Barrett, M. R. Stocker, K. D. Angielczyk, R. M. H. Smith, C. A. Sidor, G. Niedźwiedzki, A. G. Sennikov & A. J. Charig. 2017. The earliest bird-line archosaurs and the assembly of the dinosaur body plan. Nature 544: 484–487.

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

[PS17] Pardo, J. D., M. Szostakiwskyj, P. E. Ahlberg & J. S. Anderson. 2017. Hidden morphological diversity among early tetrapods. Nature 546: 642–645.

[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.

[S87] Stephens, W. J. 1887. On some additional labyrinthodont fossils from the Hawkesbury sandstones of New South Wales. (Platyceps wilkinsonii, and two unnamed specimens). Proceedings of the Linnean Society of New South Wales, series 2, 1 (4): 1175–1192.

[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.

Last updated: 30 August 2018.

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