Tetrapoda

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

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.

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 [Batrachomorpha, Colosteoidea, Eutetrapoda, Holospondyli, Labyrinthodontia, Phyllospondyli, Stegocephali]
    |--+--Elginerpeton pancheni Ahlberg 1995 AC08, RCQ03
    |  `--Obruchevichthys gracilis Vorobyeva 1977 RCQ03
    `--+--Metaxygnathus Campbell & Bell 1977 DS20, C00
       |    `--M. denticulus Campbell & Bell 1977 AC08, RCQ03
       `--+--+--Ventastega curonica Ahlberg, Luksevics & Lebedev 1994 DS20, RCQ03
          |  `--Acanthostega Jarvik 1952 DS20, D07 [Acanthostegidae]
          |       `--A. gunnari Jarvik 1952 RCQ03
          `--+--Ymeria denticulata DS20, PS17
             `--+--Perittodus DS20
                `--+--Ichthyostegidae [Ichthyostegalia] M93
                   |    |--Ichthyostegopsis wimani Säve-Söderbergh 1932 M93
                   |    `--Ichthyostega Säve-Söderbergh 1932 DS20, D07
                   |         |--I. eigili D07
                   |         |--I. kochi D07
                   |         |--I. stensioei Säve-Söderbergh 1932 RCQ03
                   |         `--I. watsoni D07
                   `--+--Whatcheeriidae C02
                      |    |--Ossinodus Warren & Turner 2004 WT04
                      |    |    `--*O. pueri Warren & Turner 2004 WT04
                      |    `--+--Whatcheeria deltae Lombard & Bolt 1995 DS20, RCQ03
                      |       `--Pederpes Clack 2002 PS17, C02
                      |            `--*P. finneyae Clack 2002 C02
                      `--+--Densignathus rowei Daeschler 2000 DS20, RCQ03
                         `--+--Tulerpeton [Tulerpetontidae] DS20
                            |    `--T. curtum Lebedev 1984 RCQ03
                            `--+--Crassigyrinus Panchen 1980 DS20, S85 [Crassigyrinidae, Palaeostegalia]
                               |    `--C. scoticus Watson 1929 RCQ03 [=Macromerium scoticum S85]
                               `--Neostegalia DS20

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
  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
  Papposaurus traquairi S85
  Cyrtopodion LK03
    |--C. heterocercus LK03
    `--C. kotschyi LK03
  Laudakia stellio LK03
  Mesalina brevirostris LK03
  Ophiomorus latastii LK03
  Eirenis LK03
    |--*E. collaris (Ménétries 1832) [=Coluber collaris] SBM01
    |--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

*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.

[SB01] 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.

[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: 9 February 2022.

Lepospondyli

Reconstruction of Odonterpeton triangulare by Smokeybjb.

Belongs within: Batrachosauria.
Contains: Nectridea, Albanerpetontidae, Gymnophiona, Anura, Caudata.

The Lepospondyli are a clade of amphibian-grade tetrapods known from the Lower Carboniferous to the Upper Permian though the living amphibians may also be nested here. The basal members of the clade were the lizard- or salamander-like microsaurs, all small animals with relatively short legs. The 'microsaurs' were paraphyletic to more derived subgroups such as the Nectridea or Lysorophia. The Lysorophia were small, serpentine animals with an extremely elongate trunk and reduced, poorly ossified limbs and girdles (Ruta et al. 2003).

The earliest clear relatives of the modern amphibians are known from the Early Triassic. Chinlestegophis jenkinsi, a probably burrowing amphibian from the Upper Triassic of Colorado, is a potential relative of caecilians, sharing with them a wide cultriform process on the skull, laterally placed eyes and double tooth rows on the mandible. The Early Jurassic Eocaecilia micropoda was even more caecilian-like as indicated by features like the loss of the tympanic ear and presence of the pseudodentary (Pardo, Small & Huttenlocker 2017). The salamanders and frogs are united in a clade Batrachia, exclusive of the caecilians, by a number of shared features such as loss of the postfrontal, surangular and splenial bones and loss of dermal scales (Frost et al. 2006). Triadobatrachus massinoti, from the early Triassic of Madagascar, was similar to a modern frog in overall appearance but retained a higher number of vertebrae, including a short tail, and was not adapted for jumping.

Lepospondyli [Hapsidopareiontidae, Holospondyli, Microbrachomorpha, Microsauria, Tuditanomorpha]
    |  i. s.: Trachystegos megalodon Carroll 1966 M93
    |--+--Trihecaton [Trihecatontidae] DS20
    |  |    `--T. howardinus Vaughn 1972 M93
    |  `--+--Nectridea DS20
    |     `--+--Microbrachidae M93
    |        |    |--Paramicrobrachis fritschi Kuhn 1959 M93
    |        |    `--Microbrachis Fritsch 1876 DS20, D07
    |        |         |--M. obtusatum D07
    |        |         `--M. pelikani Fritsch 1876 RCQ03
    |        `--Hyloplesion [Hyloplesiontidae] DS20
    |             `--H. longicostatum Fritsch 1876 RCQ03
    `--+--+--Pantylidae RCQ03
       |  |    |--Pantylus cordatus Cope 1871 DS20, RCQ03
       |  |    `--Stegotretus agyrus Berman, Eberth & Brinkman 1988 AR08, RCQ03
       |  `--Tuditanidae RCQ03
       |       |  i. s.: Boii crassidens (Fritsch 1876) M93
       |       |--Asaphestera intermedia (Dawson 1894) DS20, RCQ03
       |       `--+--Crinodon DS20
       |          `--Tuditanus punctulatus Cope 1874 DS20, RCQ03
       `--+--Saxonerpeton geinitzi (Credner 1890) AR08, RCQ03
          `--+--+--+--Rhynchonkos [Goniorhynchidae, Rhynchonkidae] DS20
             |  |  |    `--R. stovalli (Olson 1970) RCQ03
             |  |  `--+--Dvellecanus carrolli PS17
             |  |     `--Aletrimyti gaskillae PS17
             |  `--+--+--Huskerpeton englehorni PS17
             |     |  `--Gymnarthridae PS17
             |     |       |--Hylerpeton dawsoni T85
             |     |       |--Leiocephalikon problematicum C00, T85
             |     |       |--Elfridia Thayer 1985 T85
             |     |       |    `--*E. bulbidens Thayer 1985 T85
             |     |       |--Euryodus DS20
             |     |       |    |--E. dalyae AR08
             |     |       |    `--E. primus Olson 1939 RCQ03
             |     |       `--Cardiocephalus DS20
             |     |            |--C. dalyae C00
             |     |            |--C. peabodyi AR08
             |     |            `--C. sternbergi Broili 1904 RCQ03
             |     `--+--Nannaroter mckinzei PS17
             |        `--Ostodolepidae PS17
             |             |--Micraroter erythrogeios Daly 1973 DS20, RCQ03
             |             |--Pelodosotis elongatum Carroll & Gaskill 1978 DS20, RCQ03
             |             `--Ostodolepis brevispinatus Williston 1913 M93
             `--+--+--Odonterpeton [Odonterpetontidae] DS20
                |  |    `--O. triangulare Moodie 1909 RCQ03
                |  `--Sparodus Fritsch 1876 DS20, RCQ03
                |       `--S. validens RCQ03
                `--+--+--Hapsidopareion lepton Daly 1973 DS20, RCQ03
                   |  `--Llistrofus Carroll & Gaskill 1978 DS20, RCQ03
                   |       `--L. pricei Carroll & Gaskill 1978 M93
                   `--+--Brachystelechidae PS17
                      |    |--Batropetes fritschia (Geinitz & Deichmüller 1882) DS20, RCQ03
                      |    `--+--Carrolla Langston & Olson 1986 RCQ03
                      |       |    `--C. craddocki RCQ03
                      |       `--Quasicaecilia Carroll 1990 RCQ03
                      |            `--Q. texana Carroll 1990 M93
                      `--+--Lysorophia RCQ03
                         |    |--Molgophidae G88
                         |    |    |--Molgophis G88
                         |    |    `--Megamolgophis G88
                         |    `--Cocytinidae [Lysorophidae] AR08
                         |         |--Cocytinus G88
                         |         |--Lysorophus tricarinatus C07
                         |         |--Pleuroptyx clavatus C00
                         |         `--Brachydectes DS20
                         |              |--B. elongatus Wellstead 1991 RCQ03
                         |              `--B. newberryi Cope 1868 RCQ03
                         `--+--Albanerpetontidae DS20
                            `--+--+--Rileymillerus cosgriffi PSH17
                               |  `--+--Chinlestegophis Pardo, Small & Huttenlocker 2017 PSH17
                               |     |    `--*C. jenkinsi Pardo, Small & Huttenlocker 2017 PSH17
                               |     `--Parabatrachia [Apoda] FG06
                               |          |--Eocaecilia micropodia Jenkins & Walsh 1993 PS17, RCQ03
                               |          `--Gymnophiona DS20
                               `--Batrachia FB17
                                    |--Salientia RCQ03
                                    |    |  i. s.: Czatkobatrachus polonicus RR00
                                    |    |--Anura PSH17
                                    |    |--Prosalirus [Prosaliridae] C01
                                    |    |    `--P. bitis Shubin & Jenkins 1995 R00
                                    |    `--Triadobatrachus Kuhn 1962 AR08, RR00 (see below for synonymy)
                                    |         `--T. massinoti (Piveteau 1936) RCQ03
                                    |--Pangerpeton DS20
                                    |--Caudata DS20
                                    `--+--Belyanerpeton DS20
                                       `--Karauridae M00
                                            |--Karaurus sharovi Ivakhnenko 1978 DS20, RCQ03
                                            `--Kokartus honorarius M00

Triadobatrachus Kuhn 1962 AR08, RR00 [=Protobatrachus Piveteau 1936 (preoc.) RR00; Proanura, Triadobatrachidae]

*Type species of generic name indicated

REFERENCES

[AR08] Anderson, J. S., R. R. Reisz, D. Scott, N. B. Fröbisch & S. S. Sumida. 2008. A stem batrachian from the Early Permian of Texas and the origin of frogs and salamanders. Nature 453: 515–518.

[C00] Carroll, R. L. 2000. Lepospondyls. In: Heatwole, H., & R. L. Carroll (eds) Amphibian Biology vol. 4. Palaeontology. The evolutionary history of amphibians pp. 1198–1269. Surrey Beatty & Sons.

[C01] Carroll, R. 2001. Chinese salamanders tell tales. Nature 410: 534–536.

[C07] Case, E. C. 1907. Revision of the Pelycosauria of North America. Carnegie Institute of Washington Publication 55: 1–176, 35 pls.

[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.

[FB17] Feng, Y.-J., D. C. Blackburn, D. Liang, D. M. Hillis, D. B. Wake, D. C. Cannatella & P. Zhang. 2017. Phylogenomics reveals rapid, simultaneous diversification of three major clades of Gondwanan frogs at the Cretaceous–Paleogene boundary. Proceedings of the National Academy of Sciences of the USA 114 (29): E5864–E5870.

[FG06] Frost, D. R., T. Grant, J. Faivovich, R. H. Bain, A. Haas, C. F. B. Haddad, R. O. de Sá, A. Channing, M. Wilkinson, S. C. Donnellan, C. J. Raxworthy, J. A. Campbell, B. L. Blotto, P. Moler, R. C. Drewes, R. A. Nussbaum, J. D. Lynch, D. M. Green & W. C. Wheeler. 2006. The amphibian tree of life. Bulletin of the American Museum of Natural History 297: 1–370.

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

[M93] Milner, A. R. 1993. Amphibian-grade Tetrapoda. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 665–679. Chapman & Hall: London.

[M00] Milner, A. R. 2000. Mesozoic and Tertiary Caudata and Albanerpetontidae. In: Heatwole, H., & R. L. Carroll (eds) Amphibian Biology vol. 4. Palaeontology. The evolutionary history of amphibians pp. 1412–1444. Surrey Beatty & Sons.

[PSH7] Pardo, J. D., B. J. Small & A. K. Huttenlocker. 2017. Stem caecilian from the Triassic of Colorado sheds light on the origins of Lissamphibia. Proceedings of the National Academy of Sciences of the USA 114 (27): E5389–E5395.

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

[R00] Roček, Z. 2000. Mesozoic anurans. In: Heatwole, H., & R. L. Carroll (eds) Amphibian Biology vol. 4. Palaeontology. The evolutionary history of amphibians pp. 1295–1331. Surrey Beatty & Sons.

[RR00] Roček, Z., & J-C. Rage. 2000. Proanuran stages (Triadobatrachus, Czatkobatrachus). In: Heatwole, H., & R. L. Carroll (eds) Amphibian Biology vol. 4. Palaeontology. The evolutionary history of amphibians pp. 1283–1294. Surrey Beatty & Sons.

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

[T85] Thayer, D. W. 1985. New Pennsylvanian lepospondyl amphibians from the Swisshelm Mountains, Arizona. Journal of Paleontology 59 (3): 684–700.

Last updated: 9 February 2022.

Temnospondyli

Reconstruction of Dendrerpeton, from here.

Belongs within: Neostegalia.
Contains: Stereospondylomorpha, Dissorophoidea.

The Temnospondyli were one of the most significant early clades of amphibian-grade tetrapods, being recorded from the early Carboniferous (Visean) to the mid-Cretaceous (Albian). Whether they survived after this date depends on whether the modern amphibians (particularly frogs and salamanders) are accepted as derived temnospondyls. The clade as a whole is characterised by the presence of interpterygoid vacuities at least half as wide as the skull and bordered by triradiate pterygoids (Ruta et al. 2003). The majority of temnospondyls were semiaquatic, though the clade as a whole includes members varying from almost entirely terrestrial to fully aquatic.

Early Carboniferous temnospondyls include the Scottish Balanerpeton and the Nova Scotian Dendrerpeton, both medium-sized semi-terrestrial forms with the latter reaching about a metre in length. The Late Carboniferous and Early Permian Cochleosauridae were crocodile-like semi-aquatic ambush predators, reaching lengths of over 1.5 m. The Early Permian saw the appearance of even larger forms: Edops craigi reached about two metres in length whereas the three metre-long Eryops megacephalus was one of the largest land animals of its time. Eryops had a more strongly build appendicular skeleton than other temnospondyls, indicating a greater degree of adaptation for terrestrial locomotion. With the exceptions of Edops and the Cochleosauridae, most temnospondyls may be assigned to a clade Rhachitomi, basally characterised by vertebrae with a large intercentrum and smaller paired pleurocentra below the notochord.

Temnospondyli [Dvinosauria, Edopoidea, Euskelia, Limnarchia]
    |--Edops [Edopidae] DS20
    |    `--E. craigi Romer 1935 RCQ03
    `--+--Cochleosauridae SO05
       |    |--Procochleosaurus SO05
       |    `--+--Adamanterpeton ohioensis PSH17
       |       `--+--Cochleosaurus Fritsch 1885 DS20, D07
       |          |    |--C. bohemicus D07
       |          |    `--C. florensis Rieppel 1980 RCQ03
       |          `--Chenoprosopus SO05
       |               |--C. lewisi Hook 1993 RCQ03
       |               `--C. milleri Miehl 1913 M93
       `--Rhachitomi (see below for synonymy) PSH17
            |  i. s.: Peltobatrachus Panchen 1959 PSH17, D07 [Peltobatrachidae]
            |           `--P. pustulatus Panchen 1959 M93
            |--+--Parioxys M93 [Parioxyidae H00]
            |  |    |--P. bolli Carroll 1964 M93
            |  |    `--P. ferricolus Cope 1878 M93
            |  `--Eryopidae RCQ03
            |       |--Onchiodon labyrinthicus YW00, PSH17
            |       |--Eryops Miner 1925 DS20, D07
            |       |    |--E. avinoffi (Romer 1952) M93
            |       |    `--E. megacephalus Cope 1877 RCQ03
            |       `--Clamorosaurus M93
            |            |--C. borealis Gubin 1983 M93
            |            `--C. nocturnus Gubin 1983 M93
            `--+--Stereospondylomorpha DS20
               `--+--+--Palatinerpeton DS20
                  |  `--+--Iberospondylus schultzei DS20, PSH17
                  |     `--+--Dissorophoidea DS20
                  |        `--Lapillopsis [Lapillopsidae] PSH17
                  |             `--L. nanus Warren & Hutchinson 1990 PSH17, M93
                  `--+--Zatracheidae [Stegopidae] H00
                     |    |--Acanthostomatops vorax (Credner 1883) DS20, M93
                     |    |--Zatrachys serratus PSH17
                     |    |--Stegops newberryi (Cope 1875) H00, M93
                     |    `--Dasyceps H00
                     `--+--Capetus [Capetidae] DS20
                        |    `--C. palustris PSH17
                        `--+--Balanerpeton woodi Milner & Sequeira 1994 DS20, RCQ03
                           `--Dendrerpeton RCQ03 [Dendrerpetidae DS20]
                                |--D. acadianum Owen 1853 RCQ03
                                `--D. helogenes YW00

Rhachitomi [Astatodipnoa, Batrachii, Caducibranchia, Dipnoa, Eryopoidea, Lissamphibia, Paratoidia, Prosirenidae, Prosirenoidea] PSH17

*Type species of generic name indicated

REFERENCES

[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.

[H00] Holmes, R. 2000. Palaeozoic temnospondyls. In: Heatwole, H., & R. L. Carroll (eds) Amphibian Biology vol. 4. Palaeontology. The evolutionary history of amphibians pp. 1081–1120. Surrey Beatty & Sons.

[M93] Milner, A. R. 1993. Amphibian-grade Tetrapoda. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 665–679. Chapman & Hall: London.

[PSH17] Pardo, J. D., B. J. Small & A. K. Huttenlocker. 2017. Stem caecilian from the Triassic of Colorado sheds light on the origins of Lissamphibia. Proceedings of the National Academy of Sciences of the USA 114 (27): E5389–E5395.

[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.

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Last updated: 29 January 2022.