Editing Amphibian (section)

=== Caudata ===
[[File:Cryptobranchus japonicus.jpg|thumb|left|upright|alt=Japanese giant salamander|[[Japanese giant salamander]] <br/>(''Andrias japonicus''), a primitive salamander]]

The order [[Caudata]] (from the Latin ''cauda'' meaning "tail") consists of the salamanders—elongated, low-slung animals that mostly resemble lizards in form. This is a [[Symplesiomorphy|symplesiomorphic trait]] and they are no more closely related to lizards than they are to mammals.<ref>{{cite web |url=http://www.nature.com/scitable/topicpage/trait-evolution-on-a-phylogenetic-tree-relatedness-41936 |title=Trait Evolution on a Phylogenetic Tree: Relatedness, Similarity, and the Myth of Evolutionary Advancement |author=Baum, David |year=2008 |publisher=Nature Education |access-date=December 1, 2012 |archive-date=March 8, 2014 |archive-url=https://web.archive.org/web/20140308191855/http://www.nature.com/scitable/topicpage/trait-evolution-on-a-phylogenetic-tree-relatedness-41936 |url-status=live }}</ref> Salamanders lack claws, have scale-free skins, either smooth or covered with [[tubercle]]s, and tails that are usually flattened from side to side and often finned. They range in size from the [[Chinese giant salamander]] (''Andrias davidianus''), which has been reported to grow to a length of {{convert|1.8|m}},<ref>{{cite web |url=http://amphibiaweb.org/cgi/amphib_query?where-genus=Andrias&where-species=davidianus |title=''Andrias davidianus'' Chinese giant salamander |author=Sparreboom, Max |date=February 7, 2000 |publisher=AmphibiaWeb |access-date=December 1, 2012 |archive-date=December 26, 2012 |archive-url=https://web.archive.org/web/20121226102607/http://amphibiaweb.org/cgi/amphib_query?where-genus=Andrias&where-species=davidianus |url-status=live }}</ref> to the diminutive ''[[Thorius pennatulus]]'' from Mexico which seldom exceeds {{convert|20|mm|1|abbr=on}} in length.<ref>{{cite web |url=http://amphibiaweb.org/cgi/amphib_query?where-genus=Thorius&where-species=pennatulus |title=''Thorius pennatulus'' |author=Wake, David B. |date=November 8, 2000 |publisher=AmphibiaWeb |access-date=August 25, 2012 |archive-date=May 15, 2012 |archive-url=https://web.archive.org/web/20120515190809/http://amphibiaweb.org/cgi/amphib_query?where-genus=Thorius&where-species=pennatulus |url-status=live }}</ref> Salamanders have a mostly [[Laurasia]]n distribution, being present in much of the [[Holarctic]] region of the northern hemisphere. The family [[Plethodontidae]] is also found in Central America and South America north of the [[Amazon basin]];<ref name="Collins" /> South America was apparently invaded from Central America by about the start of the [[Miocene]], 23 million years ago.<ref name="Elmer2013">{{cite journal|last1=Elmer|first1=K. R.|last2=Bonett|first2=R. M.|last3=Wake|first3=D. B.|last4=Lougheed|first4=S. C.|title=Early Miocene origin and cryptic diversification of South American salamanders|journal=BMC Evolutionary Biology|volume= 13|issue=1|date= 2013-03-04|pages= 59|doi= 10.1186/1471-2148-13-59|pmid=23497060|pmc=3602097 |doi-access=free |bibcode=2013BMCEE..13...59E }}</ref> Urodela is a name sometimes used for all the [[extant taxon|extant]] species of salamanders.<ref name="larson">{{Cite journal| last1=Larson | first1=A. | last2=Dimmick | first2=W. | year=1993 | title=Phylogenetic relationships of the salamander families: an analysis of the congruence among morphological and molecular characters | journal=Herpetological Monographs | volume=7 | issue=7 | pages=77–93 | doi =10.2307/1466953 | jstor=1466953}}</ref> Members of several salamander families have become [[Neoteny|paedomorphic]] and either fail to complete their metamorphosis or retain some larval characteristics as adults.{{sfn | Dorit | Walker | Barnes | 1991 | p=852}} Most salamanders are under {{cvt|15|cm}} long. They may be terrestrial or aquatic and many spend part of the year in each habitat. When on land, they mostly spend the day hidden under stones or logs or in dense vegetation, emerging in the evening and night to forage for worms, insects and other invertebrates.<ref name="Collins" />

[[File:Triturus dobrogicus dunai tarajosgőte.jpg|thumb|alt=Danube crested newt|[[Danube crested newt]] <br/>(''Triturus dobrogicus''), an advanced salamander]]

The suborder [[Cryptobranchoidea]] contains the primitive salamanders. A number of fossil cryptobranchids have been found, but there are only three living species, the Chinese giant salamander (''Andrias davidianus''), the [[Japanese giant salamander]] (''Andrias japonicus'') and the [[hellbender]] (''Cryptobranchus alleganiensis'') from North America. These large amphibians retain several larval characteristics in their adult state; gills slits are present and the eyes are unlidded. A unique feature is their ability to feed by suction, depressing either the left side of their lower jaw or the right.<ref name="ADWCrypto">{{cite web | url=http://animaldiversity.ummz.umich.edu/site/accounts/information/Cryptobranchidae.html | title=Cryptobranchidae | author=Heying, Heather | year=2003 | work=Animal Diversity Web | publisher=University of Michigan | access-date=August 25, 2012 | archive-date=October 21, 2012 | archive-url=https://web.archive.org/web/20121021021234/http://animaldiversity.ummz.umich.edu/site/accounts/information/Cryptobranchidae.html | url-status=live }}</ref> The males excavate nests, persuade females to lay their egg strings inside them, and guard them. As well as breathing with lungs, they respire through the many folds in their thin skin, which has [[Capillary|capillaries]] close to the surface.<ref name="EHSAR">{{cite web | url=http://www.fws.gov/midwest/es/soc/amphibians/eahe-sa.pdf | title=Eastern Hellbender Status Assessment Report | author1=Mayasich, J. | author2=Grandmaison, D. | author3=Phillips, C. | date=June 1, 2003 | publisher=U.S. Fish and Wildlife Service | access-date=August 25, 2012 | archive-date=September 4, 2012 | archive-url=https://web.archive.org/web/20120904084224/http://www.fws.gov/midwest/es/soc/amphibians/eahe-sa.pdf | url-status=live }}</ref>

The suborder [[Salamandroidea]] contains the advanced salamanders. They differ from the cryptobranchids by having fused [[Mandible|prearticular bones]] in the lower jaw, and by using internal fertilisation. In salamandrids, the male deposits a bundle of sperm, the [[spermatophore]], and the female picks it up and inserts it into her [[cloaca]] where the sperm is stored until the eggs are laid.<ref name="BritCaudata">{{cite encyclopedia |url=https://www.britannica.com/EBchecked/topic/100353/Caudata |title=Caudata |author=Wake, David B |encyclopedia=Encyclopædia Britannica |access-date=August 25, 2012 |archive-date=May 16, 2013 |archive-url=https://web.archive.org/web/20130516165633/https://www.britannica.com/EBchecked/topic/100353/Caudata |url-status=live }}</ref> The largest family in this group is Plethodontidae, the lungless salamanders, which includes 60% of all salamander species. The [[Family (biology)|family]] [[Salamandridae]] includes the true salamanders and the name "[[newt]]" is given to members of its subfamily [[Pleurodelinae]].{{sfn | Stebbins | Cohen | 1995 | p=3 }}

The third suborder, [[Sirenoidea]], contains the four species of sirens, which are in a single family, [[Sirenidae]]. Members of this order are [[eel]]-like aquatic salamanders with much reduced forelimbs and no hind limbs. Some of their features are primitive while others are derived.<ref>{{cite book |author=Cogger, H. G. |editor=Zweifel, R. G |year=1998 |title=Encyclopedia of Reptiles and Amphibians |publisher= Academic Press |pages= 69–70 |isbn=978-0-12-178560-4}}</ref> Fertilisation is likely to be external as sirenids lack the cloacal glands used by male salamandrids to produce spermatophores and the females lack [[spermatheca]]e for sperm storage. Despite this, the eggs are laid singly, a behaviour not conducive for external fertilisation.<ref name="BritCaudata" />