Clade of amphibians
Not to be confused with the phylum
Chordata
.
The
Caudata
are a group of
amphibians
containing the extant
salamanders
(the
order
Urodela) and all extinct species of amphibians more closely related to salamanders than to frogs. They are typically characterized by a superficially
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.
Disagreement exists between different authorities as to the definition of the terms "Caudata" and "Urodela". Some maintain that Urodela should be restricted to the
crown group
, with Caudata being used for the
total group
. Others restrict the name Caudata to the crown group and use Urodela for the total group. The former approach seems to be most widely adopted and is used in this article.
[1]
Evolution
[
edit
]
The origins and evolutionary relationships between the three main groups of amphibians (
apodans
,
urodeles
and
anurans
) is a matter of debate. A 2005 molecular phylogeny, based on
rDNA
analysis, suggested that the first divergence between these three groups took place soon after they had branched from the
lobe-finned fish
in the
Devonian
(around 360 million years ago), and before the breakup of the supercontinent
Pangaea
. The briefness of this period, and the speed at which radiation took place, may help to account for the relative scarcity of amphibian fossils that appear to be closely related to
lissamphibians
.
[2]
However, more recent studies have generally found more recent (Late
Carboniferous
[3]
to Early
Permian
[4]
) age for the basalmost divergence among lissamphibians.
The earliest known fossil salamanders include
Kokartus honorarius
from the
Middle Jurassic
of
Kyrgyzstan
and three species of the apparently neotenic, aquatic
Marmorerpeton
from England
[5]
and Scotland
[6]
of a similar date.
[7]
Karaurus
,
Kokartus
, and
Marmorerpeton
are together grouped in the extinct group
Karauridae
according to the structure of their skull and vertebrae.
[6]
They looked superficially like robust modern salamanders but lacked a number of anatomical features that characterise all modern salamanders.
Karaurus sharovi
from the
Upper Jurassic
of Kazakhstan resembled modern
mole salamanders
in morphology and probably had a similar burrowing lifestyle.
[1]
In 2020, new specimens of the previously enigmatic tetrapod
Triassurus
from the Middle Triassic of Kyrgyzstan were described, revealing it to be the oldest known caudatan
[8]
and this conclusion has been supported by subsequent analyses.
[6]
The
Cryptobranchoidea
and the
Salamandroidea
, also known as Diadectosalamandroidei, are likely
sister groups
. Some studies suggest that both groups appeared before the end of the Jurassic, the former being exemplified by
Chunerpeton tianyiensis
,
Pangerpeton sinensis
,
Jeholotriton paradoxus
,
Regalerpeton weichangensis
,
Liaoxitriton daohugouensis
and
Iridotriton hechti
, and the latter by
Beiyanerpeton jianpingensis
. By the
Upper Cretaceous
, most or all of the living salamander families had probably appeared.
[1]
However, recent phylogenetic analysis suggest that several fossil species previously thought to represent
crown group
salamanders may actually represent members of the
stem group
.
[6]
Cryptobranchoidea
are sometimes referred to as primitive salamanders whereas
Salamandroidea
/ Diadectosalamandroidei are referred to as advanced salamanders. However, these lables are not necessarily helpful and imply that all members of
Cryptobranchoidea
are unchanged and represent the ancestral condition which is not supported by the fossil record.
[6]
All known extant and extinct (fossil) salamanders fall under the
total group
Caudata
, whereas the common ancestor of all extant salamanders and all of its desendents (extinct and extant) represent the less inclusive
crown group
Urodela.
[9]
[10]
There are about 758 extant species of salamander.
[11]
References
[
edit
]
- ^
a
b
c
Naish, Darren (2013-10-01).
"The amazing world of salamanders"
.
Scientific American
. Retrieved
2014-01-14
.
- ^
San Mauro, Diego; Vences, Miguel; Alcobendas, Marina; Zardoya, Rafael; Meyer, Axel (2005).
"Initial diversification of living amphibians predated the breakup of Pangaea"
(PDF)
.
The American Naturalist
.
165
(5): 590?599.
doi
:
10.1086/429523
.
PMID
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.
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- ^
San Mauro, D. (2010). "A multilocus timescale for the origin of extant amphibians".
Molecular Phylogenetics and Evolution
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doi
:
10.1016/j.ympev.2010.04.019
.
PMID
20399871
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- ^
Marjanovi? D, Laurin M (2007). "Fossils, molecules, divergence times, and the origin of lissamphibians".
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doi
:
10.1080/10635150701397635
.
PMID
17520502
.
- ^
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a
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c
d
e
Jones, Marc E. H.; Benson, Roger B. J.; Skutschas, Pavel; Hill, Lucy; Panciroli, Elsa; Schmitt, Armin D.; Walsh, Stig A.; Evans, Susan E. (2022-07-11).
"Middle Jurassic fossils document an early stage in salamander evolution"
.
Proceedings of the National Academy of Sciences
.
119
(30): e2114100119.
Bibcode
:
2022PNAS..11914100J
.
doi
:
10.1073/pnas.2114100119
.
ISSN
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PMC
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.
PMID
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.
- ^
Marjanovic D, Laurin M (2014). "An updated paleontological timetree of lissamphibians, with comments on the anatomy of Jurassic crown-group salamanders (Urodela)".
Historical Biology
.
26
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doi
:
10.1080/08912963.2013.797972
.
S2CID
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.
- ^
Schoch, Rainer R.; Werneburg, Ralf; Voigt, Sebastian (2020-05-26).
"A Triassic stem-salamander from Kyrgyzstan and the origin of salamanders"
.
Proceedings of the National Academy of Sciences
.
117
(21): 11584?11588.
Bibcode
:
2020PNAS..11711584S
.
doi
:
10.1073/pnas.2001424117
.
ISSN
0027-8424
.
PMC
7261083
.
PMID
32393623
.
- ^
Larson, A.; Dimmick, W. (1993). "Phylogenetic relationships of the salamander families: an analysis of the congruence among morphological and molecular characters".
Herpetological Monographs
.
7
(7): 77?93.
doi
:
10.2307/1466953
.
JSTOR
1466953
.
- ^
Blackburn, D.C.; Wake, D.B. (2011).
"Class Amphibia Gray, 1825. In: Zhang, Z.-Q. (Ed.) Animal biodiversity: An outline of higher-level classification and survey of taxonomic richness"
(PDF)
.
Zootaxa
.
3148
: 39?55.
doi
:
10.11646/zootaxa.3148.1.8
.
- ^
"State of the World's Amphibians"
.
IUCN SSC Amphibian Specialist Group
.