Batrachomorpha
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Batrachomorpha ("Frog form") is a name given to recent and extinct amphibians that are not related to reptiles. The name was coined by the Swedish palaeontologist Gunnar Säve-Söderbergh in 1934 to refer to the ichthyostegids, the labyrinthodonts, and the anurans. Friedrich von Huene adopted it as a superorder of his subclass "Eutetrapoda" (the lower tetrapods exclusive of the urodeles) and included the orders Stegocephalia (here includes a number of Labyrinthodontia and Anura; it was also used informally by Erik Jarvik (1968) but in a wider sense, to include the ancestral osteolepiform fishes. This classification is no longer followed.
Michael Benton adopted the term Batrachomorpha in a cladistic sense to include all living amphibians, their common ancestor, and extinct relatives. This is suggested as a more precise term than "Amphibia", which is not diagnostic as it simply refers to all non-amniote tetrapods. However, the phylogenetic relationships of Paleozoic tetrapods have not yet been worked out with certainty, and the validity of the clade Batrachomorpha depends on where other amphibians and early amniotes fit on the evolutionary tree, and in some phylogenies the clade is redundant (e.g. Laurin 1996).
Batrachomorphs are distinguished by a number of features in the skeleton, including a flat or shallow skull, a fused skull roof with no cranial kinesis, exoccipital-postparietal contact on the occiput, and four or fewer fingers on the hand (Benton 2000 pp.98-99).
Dr Benton contrasts Batrachomorphs with Reptiliomorphs; both are stem-based clades, but the former constitutes the "amphibian" evolutionary radiation, the later the contemporary proto-reptilian and early amniote evolution.
In the appendix to Benton 2004 (which combines cladistic and linnaean rankings) Batrachomorpha is given the taxonomic rank of Class.
[edit] References and External links
- Benton, M. J. (2000), Vertebrate Paleontology, 2nd Ed. Blackwell Science Ltd 3rd ed. 2004 - see also taxonomic hierarchy of the vertebrates, according to Benton 2004
- Laurin, Michel (1996) Terrestrial Vertebrates - Stegocephalians: Tetrapods and other digit-bearing vertebrates
- Marjanović, David, (2002) Re: thoughts on which nodes to name Dinosaur Mailing List
- von Huene, F., 1956, Paläontologie und Phylogenie der niederen Tetrapoden, G. Fischer, Jena.
- Jarvik, E. (1968). Aspects of vertebrate phylogeny. In: Current Problems of Lower Vertebrate Phylogeny (ed. T. Ørvig), Nobel Symposium 4, pp. 497-527. Stockholm, Almqvist & Wiksell.
- Säve-Söderbergh, G. (1934). Some points of view concerning the evolution of the vertebrates and the classification of this group. Arkiv för Zoologi 26A: 1-20.
