Belongs within: Tetrapodomorpha.
Contains: 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. The Early Carboniferous Whatcheeriidae may have been the earliest tetrapods to spend significant amounts of time on land.
Synapomorphies (from Ahlberg et al. 2008): Supracleithrum and post-temporal absent; scapulocoracoid enlarged; coracoid foramen absent; interclavicle enlarged; sacrum present.
Tetrapoda [Batrachomorpha, Colosteoidea, Eutetrapoda, Labyrinthodontia, Phyllospondyli, Stegocephali]
|--+--Elginerpeton pancheni Ahlberg 1995AC08, RCQ03
| `--Obruchevichthys gracilis Vorobyeva 1977RCQ03
`--+--Metaxygnathus Campbell & Bell 1977DS20, C00
| `--M. denticulus Campbell & Bell 1977AC08, RCQ03
`--+--+--Ventastega curonica Ahlberg, Luksevics & Lebedev 1994DS20, RCQ03
| `--Acanthostega Jarvik 1952DS20, D07 [Acanthostegidae]
| `--A. gunnari Jarvik 1952RCQ03
`--+--Ymeria denticulataDS20, PS17
`--+--PerittodusDS20
`--+--Ichthyostegidae [Ichthyostegalia]M93
| |--Ichthyostegopsis wimani Säve-Söderbergh 1932M93
| `--Ichthyostega Säve-Söderbergh 1932DS20, D07
| |--I. eigiliD07
| |--I. kochiD07
| |--I. stensioei Säve-Söderbergh 1932RCQ03
| `--I. watsoniD07
`--+--WhatcheeriidaeC02
| |--Ossinodus Warren & Turner 2004WT04
| | `--*O. pueri Warren & Turner 2004WT04
| `--+--Whatcheeria deltae Lombard & Bolt 1995DS20, RCQ03
| `--Pederpes Clack 2002PS17, C02
| `--*P. finneyae Clack 2002C02
`--+--Densignathus rowei Daeschler 2000DS20, RCQ03
`--+--Tulerpeton [Tulerpetontidae]DS20
| `--T. curtum Lebedev 1984RCQ03
`--+--NeostegaliaDS20
`--Crassigyrinus Panchen 1980DS20, S85 [Crassigyrinidae, Palaeostegalia]
`--C. scoticus Watson 1929RCQ03 [=Macromerium scoticumS85]
Tetrapoda incertae sedis:
Sinostega Zhu & Ahlberg in Zhu, Ahlberg et al. 2002ZA02
`--*S. pani Zhu & Ahlberg in Zhu, Ahlberg et al. 2002ZA02
Hynerpeton bassetti Daeschler, Shubin et al. 1994RCQ03
Callobatrachus sanyanensisZBH03
Mesophyne beipiaoensisZBH03
Livoniana multidentata Ahlberg, Lukseviks & Mark-Kurik 2000RCQ03
LabyrinthodonW70
|--L. jaegeriW70
`--L. leptognathusW70
Diadetognathus varvicensisW70
Papposaurus traquairiS85
CyrtopodionLK03
|--C. heterocercusLK03
`--C. kotschyiLK03
Laudakia stellioLK03
Mesalina brevirostrisLK03
Ophiomorus latastiiLK03
EirenisLK03
|--*E. collaris (Ménétries 1832) [=Coluber collaris]SBM01
|--E. modestusLK03
`--E. rothiLK03
Rhynchocalamus melanocephalusLK03
Platyceps Stephens 1887S87
`--*P. wilkinsonii Stephens 1887S87
Gondwanosaurus bijoriensisS87
Ruhuhuaria reisziNB17
Stanocephalosaurus pronusNB17
MandagomphodonNB17
|--M. attridgeiNB17
`--M. hirschsoniNB17
Stenaulorhynchus stockleyiNB17
Chorophilus triseriatus [incl. C. septentrionalis]W06
Tachydromus amurensisW06
Taphrometopon lineolatumW06
Geomolge fischeriW06
ChondrotusW06
|--C. aterrimusW06
`--C. decorticatusW06
*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.
[C00] Clack, J. A. 2000. The origin of tetrapods. In: Heatwole, H., & R. L. Carroll (eds) Amphibian Biology vol. 4. Palaeontology. The evolutionary history of amphibians pp. 979–1029. Surrey Beatty & Sons.
[C02] Clack, J. A. 2002. An early tetrapod from ‘Romer’s Gap’. Nature 418: 72–76.
[DS20] Daza, J. D., E. L. Stanley, A. Bolet, A. M. Bauer, J. S. Arias, A. Čerňanský, J. J. Bevitt, P. Wagner & S. E. Evans. 2020. Enigmatic amphibians in mid-Cretaceous amber were chameleon-like ballistic feeders. Science 370: 687–691.
[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.
[LK03] Lymberakis, P., & A. Kalionzopoulou. 2003. Additions to the herpetofauna of Syria. Zoology in the Middle East 29: 33–39.
[M93] Milner, A. R. 1993. Amphibian-grade Tetrapoda. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 665–679. Chapman & Hall: London.
[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.
[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.
[SBM01] Schätti, B., I. Baran & P. Maunoir. 2001. Taxonomie, Morphologie und Verbreitung der Masken-Schlanknatter Coluber (s. l.) collaris (Müller, 1878). Revue Suisse de Zoologie 108 (1): 11–30.
[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.
[WT04] Warren, A., & S. Turner. 2004. The first stem tetrapod from the Lower Carboniferous of Gondwana. Palaeontology 47: 151–184.
[W06] Werner, F. 1906. Die nördlichsten Reptilien und Batrachier. In: Römer, F., & F. Schaudinn (eds) Fauna Arctica. Eine Zusammenstellun der arktischen Tierformen, mit besonder Berücksichtigung des Spitzbergen-Gebietes auf Grund der Ergebnisse der Deutschen Expedition in das Nördliche Eismeer im Jahre 1898 vol. 4 pp. 527–544. Gustav Fischer: Jena.
[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.