Urodela
85820
225643720
2008-07-14T18:26:14Z
12.215.179.204
{{Mergeto|Salamander|date=July 2007|User:SMcCandlish}}
{{Cleanup|date=March 2007}}
{{ActiveDiscuss}}
{{Taxobox
| name = Salamanders, Newts and relatives
| trend = down
| image = Salamandra salamandra (Marek Szczepanek).jpg
| image_width = 300px
| image_caption= [[Fire Salamander]], ''Salamandra salamandra''
| regnum = [[Animal]]ia
| phylum = [[Chordate|Chordata]]
| classis = [[Amphibia]]
| ordo = [[Caudata]]/Urodela
}}
'''Urodela''' is the [[amphibia]]n [[order (biology)|order]] comprised of [[salamanders]] and [[newts]].
== Distribution ==
Urodela is one of three orders composing the modern class amphibia. The order Urodela makes up 9% of global amphibian species equalling 558 species out of 6153 species of amphibians worldwide. [[Anurans]] are the most numerous amphibian order while [[gymnophiona]] is the least numerous.
Newts and salamanders are found on all continents except for most of Africa, Australia and Antarctica. One-third of the known urodeles, are found in North America. The highest concentration of these is found in the [[Appalachian Mountains]] region and doesn't exist any longer.
== Meaning ==
The name ''Urodela'' is derived from [[Greek language|Greek]]. The word can be divided into 2 parts. ' ''Ur'' ' & ' ''delos'' ' - Ur = [[tail]]; Delos = visible.<br />
They have another name: ''Caudata''. ''Cauda'' means [[tail]] in Latin. <br />The meaning of Urodela/Caudata is an animal with a body which is lizard-like and '''has a distinct post-anal tail'''
== Biology ==
The newts appear to be rather [[primitive amphibians]] because they have a rather simple shape.<ref>[http://www-biol.paisley.ac.uk/Courses/Tatner/biomedia/units/amph4.htm Amphibians - Order Urodela<!-- Bot generated title -->]</ref>
Note that their legs are rather weak and small, and that the body often partly drags along the ground when the animal is moving. They rely on lateral undulations of the body to assist with movement. But these primitive features are probably deceptive, and there is no evidence to suggest that they arose any earlier than the other orders of modern amphibia.
== Characteristics ==
1. Two pairs of weak and equal limbs are present.<br />
2. Skin is without [[exoskeleton]].<br />
3. Teeth are Present on both jaws.<br />
4. [[Tympanum (zoology)|Tympanum]] is present.<br />
5. Eyelids may be present or absent<br />
6. Gills are retained throughout ([[perinnibranchiates]]) the life. In some they are lost in the adults ([[caducibranchiates]]).<br />
7. Well developed [[Lateral Line sense organs]] are present. <br />
8. They show a transition of aquatic life to terrestrial mode of life. <br />
9. ''Necturus'' like animals are completely aquatic, but some animals like ''Amphiuma'' are traditional forms losing gills but retaining gills slits, while ''Ambystoma'' is a complete lung breathing form of adult condition.
== Examples ==
'''Necturus (mud puppy)''': It is with external gills and [[lateral line sense organs]]. Lungs are greatly reduced. It is found in eastern parts of USA.<br />
'''Amphiuma (Congo eel)''': External gills are absent. Limbs are rudimentary. RBCs are largest among that of the vertebrates. It if found in the southern parts of N. America. <br />
<gallery>
Image:Necturus maculosus maculosus.jpg| Necturus
Image:Amphiuma means.jpg|Amphiuma
Image:Tylotriton verrucosus gab.jpg|Tylotriton
</gallery>
'''Ambystoma:''' It is a terrestrial [[newt]]. Larva is [[Axolotl]]. Axolotl larva becomes sexually mature with out [[metamorphosis]] due to lack of iodine in the extremely cold water, in which it lives. [[Iodine]] is required for the secretion of [[thyroxine]], which stimulates the metamorphosis in [[amphibians]]. Deficiency of the thyroxine results in extended larval condiitions and precocious [[sexual maturity]], which is called [[neoteny]]. It leads to [[paedogenesis]]. <br />
'''Andrias''': These are the giant [[salamanders]] of [[China]] and [[Japan]] and are the largest caudate known. <br />
'''Tylototriton''': It occurs in the eastern [[Himalayas]] region and is the only [[India]]n caudate species.
== See also ==
1. [[Salamander]] <br />
2. [[Amphiuma]] <br />
3. [[Necturus]] or [[mud puppy]] <br />
4. [[Cryptobranchidae]]
== References ==
{{reflist}}
[[Category:Amphibians]]
[[sl:Repati krkoni]]