The Batrachomorpha ("frog forms") are a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

containing recent and extinct

amphibian Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arbor ...

s that are more closely related to modern amphibians than they are to

mammals Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), f ...

and

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates ( lizards and snakes) and rhynchoce ...

s. According to many analyses they include the extinct

Temnospondyli Temnospondyli (from Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carb ...

; some show that they include the Lepospondyli instead. The name traditionally indicated a more limited group. The first

tetrapod Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct therapsid ...

s were all amphibians in the physiological sense that they laid their eggs in water, and are colloquially sometimes referred to as

labyrinthodont "Labyrinthodontia" (Greek, 'maze-toothed') is an informal grouping of extinct predatory amphibians which were major components of ecosystems in the late Paleozoic and early Mesozoic eras (about 390 to 150 million years ago). Traditionally consi ...

s or

stegocephalia Stegocephali (often spelled Stegocephalia) is a group containing all four-limbed vertebrates. It is equivalent to a broad definition of Tetrapoda: under this broad definition, the term "tetrapod" applies to any animal descended from the first ve ...

ns. 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 In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor ...

of modern amphibians, the

Lissamphibia The Lissamphibia is a group of tetrapods that includes all modern amphibians. Lissamphibians consist of three living groups: the Salientia (frogs, toads, and their extinct relatives), the Caudata (salamanders, newts, and their extinct relatives), ...

, and its relatives. In this scheme, the name Batrachomorpha is given to this branch of amphibians, while the name

Reptiliomorpha Reptiliomorpha (meaning reptile-shaped; in PhyloCode known as ''Pan-Amniota'') is a clade containing the amniotes and those tetrapods that share a more recent common ancestor with amniotes than with living amphibians (lissamphibians). It was def ...

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.Laurin, M. (1996)
Phylogeny of Stegocephalians
from the

Tree of Life Web Project The Tree of Life Web Project is an Internet project providing information about the diversity and phylogeny of life on Earth. This collaborative peer reviewed project began in 1995, and is written by biologists from around the world. The site h ...

All other living tetrapods (

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s and

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fu ...

s) are descended from one branch of reptiliomorphs, the

amniotes Amniotes are a clade of tetrapod vertebrates that comprises sauropsids (including all reptiles and birds, and extinct parareptiles and non-avian dinosaurs) and synapsids (including pelycosaurs and therapsids such as mammals). They are dist ...

. Amniotes achieved dominance, while all other reptiliomorphs and most batrachomorphs have gone extinct.

Classification

Etymology

The name Batrachomorpha was coined by the Swedish

palaeontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of foss ...

Gunnar Säve-Söderbergh in 1934 to refer to ichthyostegids, temnospondyls, anthracosaurs, and the

frog A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" ''Triadobatrachus'' is ...

s. Säve-Söderbergh held the view that

salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten ...

s and

caecilian Caecilians (; ) are a group of limbless, vermiform or serpentine amphibians. They mostly live hidden in the ground and in stream substrates, making them the least familiar order of amphibians. Caecilians are mostly distributed in the tropics of ...

s are not related to the other

s, but had developed independently from a different group of

lobe-finned fish Sarcopterygii (; ) — sometimes considered synonymous with Crossopterygii () — is a taxon (traditionally a class or subclass) of the bony fishes known as the lobe-finned fishes. The group Tetrapoda, a mostly terrestrial superclass includ ...

, the porolepiformes. In this view

amphibians Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arbore ...

would be a biphyletic group, and Batrachomorpha was erected to form a natural group consisting of the "true amphibians" (i.e.

s in Säve-Söderberghs view) and their fossil relatives. The salamanders and the Lepospondyli was consigned to " Urodelomorpha".

Friedrich von Huene Friedrich von Huene, born Friedrich Richard von Hoinigen, (March 22, 1875 – April 4, 1969) was a German paleontologist who renamed more dinosaurs in the early 20th century than anyone else in Europe. He also made key contributions about v ...

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 In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...

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

Phylogenetics

PSM V27 D633 Skull of eryops megacephalus

Michael Benton Michael James Benton One or more of the preceding sentences incorporates text from the royalsociety.org website where: (born 8 April 1956) is a British palaeontologist, and professor of vertebrate palaeontology in the School of Earth Sciences ...

adopted the term Batrachomorpha to include all living

amphibia Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arbore ...

ns and extinct relatives more closely related to

than to

. In his scheme, Batrachomorpha is a superorder of amphibious tetrapods containing the following subgroups: * Superorder Batrachomorpha ** †Order Edopoidea ** †Family Dendrerpetonidae ** Order unnamed *** †Suborder Dvinosauria *** †Family

Branchiosauridae Branchiosauridae is an extinct family of small amphibamiform temnospondyls with external gills and an overall juvenile appearance. The family has been characterized by hundreds of well-preserved specimens from the Permo-Carboniferous of Middle ...

*** †Family Dissorophidae *** Infraclass

**** †Family Albanerpetonidae **** Order Gymnophiona (

extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extin ...

) **** Order

Urodela Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten ...

(

) **** Order Anura (

) ** †Order unnamed *** †Family †

Eryopidae Eryopidae were a group of medium to large amphibious temnospondyli, known from North America and Europe. They are defined as all eryopoids with interpterygoid vacuities (spaces in the interpterygoid bone) that are rounded at the front; and lar ...

*** †Family Actinodontidae *** †Family

Archegosauridae Archegosauridae is a family of relatively large and long snouted temnospondyls that lived in the Permian period. They were fully aquatic animals, and were metabolically and physiologically more similar to fish than modern amphibians.Florian Witzm ...

*** †Family

Rhinesuchidae Rhinesuchidae is a family of tetrapods that lived primarily in the Permian period. They belonged to the broad group Temnospondyli, a successful and diverse collection of semiaquatic tetrapods which modern amphibians are probably descended from. ...

*** †Suborder Capitosauria *** †Suborder Trematosauria **** †Family

Trematosauridae Trematosauridae are a family of large marine temnospondyl amphibians with many members. They first appeared during the Induan age of the Early Triassic, and existed until around the Carnian stage of the Late Triassic, although by then they wer ...

**** †Family Metoposauridae **** †Family Plagiosauridae **** †Family Rhytidosteidae **** †Family Brachyopidae **** †Family Chigutisauridae The other groups of tetrapods considered more closely related to

are put in the superorder

. The phylogenetic relationships of Paleozoic tetrapods have not yet been worked out with certainty, and the validity of Batrachomorpha as a

depends on where other amphibians and early amniotes fit on the evolutionary tree. The actual content of Batrachomorpha as cladistically defined is therefore uncertain, and in some phylogenies the clade is redundant (e.g. Laurin 1996).

Anatomy

Batrachomorphs are distinguished by a number of features in the skeleton, including a flat or shallow skull, a fused

skull roof The skull roof, or the roofing bones of the skull, are a set of bones covering the brain, eyes and nostrils in bony fishes and all land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium. In comparat ...

with no cranial kinesis, exoccipital- postparietal contact on the

occiput The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobes of the cer ...

, and four or fewer fingers on the hand.Benton, M. J. (2000), Vertebrate Paleontology, 2nd Ed. Blackwell Science Ltd 3rd ed, pp.98-99 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 Vertebrate paleontology is the subfield of paleontology that seeks to discover, through the study of fossilized remains, the behavior, reproduction and appearance of extinct animals with vertebrae or a notochord. It also tries to connect, by ...

, 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.

References

General references

* Benton, M.J. (2004
taxonomic hierarchy of the vertebrates
* Marjanović, David, (2002

Dinosaur Mailing List * 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. {{Taxonbar, from=Q2521462 Amphibians