Batrachomorpha
Encyclopedia
Batrachomorpha ("Frog form") is a name traditionally given to recent and extinct amphibian
s that are not related to reptile
s. It most often includes the extinct groups Temnospondyli
and Lepospondyli
.
in 1934 to refer to ichthyostegids
, temnospondyls
, anthracosaurs
, and the anurans. Säve-Söderbergh held the view that salamander
s and caecilian
s are not related to the other tetrapod
s, but had developed independently from a different group of lobe-fined 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. frog
s 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 anurans). 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 fossile relatives now being classefied together in the group Lissamphibia
.
adopted the term Batrachomorpha to include all living amphibians and extinct relatives more closely related to amphibians than to reptiles. In his scheme, Batracomorpha is a subclass of Amphibia, containing the following orders:
The other groups of tetrapods considered more closely related to amniotes are put in the subclass Reptiliomorpha
.
The phylogenetic relationships of Paleozoic tetrapods have not yet been worked out with certainty, and the validity of Batrachomorpha as a clade
depends on where other amphibians and early amniotes fit on the evolutionary tree. The actual content of Batracomorpha as cladistically defined is therefore uncertain, and in some phylogenies the clade is redundant (e.g. Laurin 1996).
with no cranial kinesis
, exoccipital-postparietal contact on the occiput
, and four or fewer fingers on the hand.
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 Vertebrate Palaeontology
, Benton (which combines cladistic and linnaean rankings) has given Batrachomorpha the rank of Subclass in his 2001 edition and Class in the 2004 edition.
Batrachomorpha ("Frog form") is a name traditionally given to recent and extinct amphibian
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...
s that are not related to reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
s. It most often includes the extinct groups Temnospondyli
Temnospondyli
Temnospondyli is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous, Permian, and Triassic periods. A few species continued into the Cretaceous. Fossils have been found on every continent...
and Lepospondyli
Lepospondyli
Lepospondyli are a group of small but diverse Carboniferous to early Permian tetrapods. Six different groups are known, the Acherontiscidae, Adelospondyli, Aïstopoda, Lysorophia, Microsauria and Nectridea, and between them they include newt-like, eel- or snake-like, and lizard-like forms, along...
.
Origin of the term
The name Batrachomorpha was coined by the Swedish palaeontologist Gunnar Säve-SöderberghGunnar Säve-Söderbergh
Gunnar Säve-Söderbergh was a Swedish palaeontologist and geologist. Säve-Söderbergh was born at Falun, the son of the neurologist Gotthard Söderbergh and Inga Säve. He passed his G.C.E. at Gothenburg in 1928 and took bachelor's and licentiate's degrees at Uppsala University in 1931 and 1933,...
in 1934 to refer to ichthyostegids
Ichthyostega
Ichthyostega is an early tetrapod genus that lived at the end of the Upper Devonian period . It was a labyrinthodont, one of the first fossil record of tetrapods. Ichthyostega possessed lungs and limbs that helped it navigate through shallow water in swamps...
, temnospondyls
Temnospondyli
Temnospondyli is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous, Permian, and Triassic periods. A few species continued into the Cretaceous. Fossils have been found on every continent...
, anthracosaurs
Anthracosauria
Anthracosauria is an order of extinct reptile-like amphibians that flourished during the Carboniferous and early Permian periods, although precisely which species are included depends on one's definition of the taxon.-Various definitions:...
, and the anurans. Säve-Söderbergh held the view that salamander
Salamander
Salamander is a common name of approximately 500 species of amphibians. They are typically characterized by a superficially lizard-like appearance, with their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant...
s and caecilian
Caecilian
The caecilians are an order of amphibians that superficially resemble earthworms or snakes. They mostly live hidden in the ground, making them the least familiar order of amphibians. All extant caecilians and their closest fossil relatives are grouped as the clade Apoda. They are mostly...
s are not related to the other tetrapod
Tetrapod
Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...
s, but had developed independently from a different group of lobe-fined fish
Sarcopterygii
The Sarcopterygii or lobe-finned fishes – sometimes considered synonymous with Crossopterygii constitute a clade of the bony fishes, though a strict classification would include the terrestrial vertebrates...
, the porolepiformes
Porolepiformes
Porolepiformes is an order of prehistoric lobe-finned fish which lived during the Devonian period . The group contains two families: Holoptychiidae and Porolepididae....
. 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. frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
s in Säve-Söderberghs view) and their fossil relatives. The salamanders and the Lepospondyli
Lepospondyli
Lepospondyli are a group of small but diverse Carboniferous to early Permian tetrapods. Six different groups are known, the Acherontiscidae, Adelospondyli, Aïstopoda, Lysorophia, Microsauria and Nectridea, and between them they include newt-like, eel- or snake-like, and lizard-like forms, along...
was consigned to "Urodelomorpha".
Friedrich von Huene
Friedrich von Huene
Friedrich von Huene was a German paleontologist who named more dinosaurs in the early 20th century than anyone else in Europe.-Biography:...
adopted it as a superorder of his subclass "Eutetrapoda" (the lower tetrapods exclusive of the urodeles) and included the orders Stegocephalia
Stegocephalia
Stegocephalia is an old term for early amphibians, comprising all pre-Jurassic and some later extinct large amphibians of more or less salamander-like build...
(here including a number of labyrinthodonts) and anurans). Erik Jarvik
Erik Jarvik
Anders Erik Vilhelm Jarvik was a Swedish palaeozoologist who worked extensively on the sarcopterygian fish Eusthenopteron...
, 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
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...
of living amphibians in the 1990s. Jarviks classification is no longer followed, all living amphibians and their fossile relatives now being classefied together in the group Lissamphibia
Lissamphibia
The subclass Lissamphibia includes all recent amphibians and means smooth amphibia.Extant amphibians fall into one of three orders — the Anura , the Caudata or Urodela , and the Gymnophiona or Apoda .Although the ancestry of each group is still unclear, all share certain common characteristics,...
.
Phylogenetics
Michael BentonMichael J. Benton
Michael J. Benton is a British paleontologist, a Fellow of the Royal Society of Edinburgh, and professor of vertebrate palaeontology in the Department of Earth Sciences at the University of Bristol....
adopted the term Batrachomorpha to include all living amphibians and extinct relatives more closely related to amphibians than to reptiles. In his scheme, Batracomorpha is a subclass of Amphibia, containing the following orders:
- Subclass Batrachomorpha
- Order TemnospondyliTemnospondyliTemnospondyli is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous, Permian, and Triassic periods. A few species continued into the Cretaceous. Fossils have been found on every continent...
†ExtinctionIn biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point... - Order AïstopodaAïstopodaAïstopoda is an order of highly specialised snake-like amphibians known from the Carboniferous and Early Permian of Europe and North America, ranging from tiny forms only , to nearly in length...
†ExtinctionIn biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point... - Order NectrideaNectrideaNectridea is an extinct order of lepospondyl amphibians from the Carboniferous and Permian periods, which included animals such as Diplocaulus. In appearance, they would have resembled modern newts or aquatic salamanders. They had long flattened tails to aid in swimming, and well-developed hind...
†ExtinctionIn biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point... - Order MicrosauriaMicrosauriaMicrosauria is an extinct order of lepospondyl amphibians from the late Carboniferous and early Permian periods. It is the most diverse and species-rich group of lepospondyls. Recently, Microsauria has been considered paraphyletic, as several other non-microsaur lepospondyl groups such as...
†ExtinctionIn biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point... - Order Gymnophiona (extant)
- Order Urodela (extant)
- Order Anura (extant)
- Order Temnospondyli
The other groups of tetrapods considered more closely related to amniotes are put in the subclass Reptiliomorpha
Reptiliomorpha
Reptiliomorpha refers to an order or subclass of reptile-like amphibians, which gave rise to the amniotes in the Carboniferous. Under phylogenetic nomenclature, the Reptiliomorpha includes their amniote descendants though, even in phylogenetic nomenclature, the name is mostly used when referring to...
.
The phylogenetic relationships of Paleozoic tetrapods have not yet been worked out with certainty, and the validity of Batrachomorpha as a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
depends on where other amphibians and early amniotes fit on the evolutionary tree. The actual content of Batracomorpha 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 roofSkull 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, hence the alternative name dermatocranium...
with no cranial kinesis
Cranial kinesis
Cranial kinesis is the term for significant movement of skull bones relative to each other in addition to movement at the joint between the upper and lower jaw. It is usually taken to mean relative movement between the upper jaw and the braincase....
, exoccipital-postparietal contact on the occiput
Occipital bone
The occipital bone, a saucer-shaped membrane bone situated at the back and lower part of the cranium, is trapezoidal in shape and curved on itself...
, and four or fewer fingers on the hand.
Dr Benton
Michael J. Benton
Michael J. Benton is a British paleontologist, a Fellow of the Royal Society of Edinburgh, and professor of vertebrate palaeontology in the Department of Earth Sciences at the University of Bristol....
contrasts Batrachomorphs with Reptiliomorphs
Reptiliomorpha
Reptiliomorpha refers to an order or subclass of reptile-like amphibians, which gave rise to the amniotes in the Carboniferous. Under phylogenetic nomenclature, the Reptiliomorpha includes their amniote descendants though, even in phylogenetic nomenclature, the name is mostly used when referring to...
; 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 Vertebrate Palaeontology
Vertebrate Palaeontology (Benton)
Vertebrate Palaeontology is a basic textbook on vertebrate paleontology by Michael J. Benton, published by Blackwell's. It has so far appeared in three editions, published in 1990, 1997, and 2005...
, Benton (which combines cladistic and linnaean rankings) has given Batrachomorpha the rank of Subclass in his 2001 edition and Class in the 2004 edition.
General 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
- Jarvik, E.Erik JarvikAnders Erik Vilhelm Jarvik was a Swedish palaeozoologist who worked extensively on the sarcopterygian fish Eusthenopteron...
(1968). Aspects of vertebrate phylogeny. In: Current Problems of Lower Vertebrate Phylogeny (ed. T. Ørvig), Nobel Symposium 4, pp. 497–527. Stockholm, Almqvist & Wiksell.