Батрахоморфтар клады: Амфибиялардың эволюциясы және жіктелуі

Clade of amphibians

The Batrachomorpha ("frog forms") are a clade containing extant and extinct amphibians that are more closely related to modern amphibians than they are to mammals and reptiles (including birds). According to many analyses they include the extinct Temnospondyli; some show that they include the Lepospondyli instead. The name traditionally indicated a more limited group. The first tetrapods were all amphibians in the physiological sense that they laid their eggs in water, and are colloquially sometimes referred to as labyrinthodonts or stegocephalians. The term "amphibians" can be ambiguous, however. In modern phylogeny, the basalmost tetrapods are discerned from two derived branches, one consisting of the crown group of modern amphibians, the Lissamphibia, and its relatives. In this scheme, the name Batrachomorpha is given to this branch of amphibians, while the name Reptiliomorpha denotes the other branch. While the actual phylogeny of the modern amphibians is not well understood, their ancestors are descended from one line of batrachomorphs. All other living tetrapods (reptiles, birds and mammals) are descended from one branch of reptiliomorphs, the amniotes. Amniotes achieved dominance, while all other reptiliomorphs and most batrachomorphs have gone extinct.

The name Batrachomorpha was coined by the Swedish palaeontologist Gunnar Säve Söderbergh in 1934 to refer to ichthyostegids, temnospondyls, anthracosaurs, and the frogs. Säve Söderbergh held the view that salamanders and caecilians are not related to the other tetrapods, but had developed independently from a different group of lobe finned fish, the porolepiformes. In this view amphibians would be a biphyletic group, and Batrachomorpha was erected to form a natural group consisting of the "true amphibians" (i. e. frogs in Säve Söderberghs view) and their fossil relatives. The salamanders and the Lepospondyli was consigned to "Urodelomorpha". 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 including a number of Labyrinthodonts) and Anura. Erik Jarvik, who took over Säve Söderberghs work and shared his view of the origin of salamanders, used the term more informally, but in a wider sense, to include the ancestral osteolepiform fishes. Though never a majority view, the notion that tetrapods had evolved twice, together with the usage of the term batrachomorpha, lingered until genetic analysis started confirming the monophyly of living amphibians in the 1990s. Jarviks classification is no longer followed, all living amphibians and their fossil relatives now being classified together in the group Lissamphibia.

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 contrasts Batrachomorphs with Reptiliomorphs; both are stem based clades; the former constitutes the "amphibian" evolutionary radiation, the latter the contemporary proto reptilian and early amniote evolution. In the appendix to Vertebrate Palaeontology, which combines cladistic and linnaean rankings, Benton has given Batrachomorpha the rank of Subclass in his 2001 edition, Class in the 2004 edition, and Superorder in the 2014 edition.