Urodela

From Wikipedia, the free encyclopedia

This article may require cleanup to meet Wikipedia's quality standards.
Please discuss this issue on the talk page or replace this tag with a more specific message.
This article has been tagged since March 2007.

Some information in this article or section is not attributed to sources and may not be reliable.
Please check for inaccuracies, and modify and cite sources as needed.

This Order (biology) includes Salamanders and Newts.

1 Distribution
2 Meaning
3 Chararteristics
4 Examples
5 See Also
6 References

[edit] Distribution

The newts appear to be rather primitive amphibians because they have a rather simple shape.

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.

Most newts and salamanders are found in North America, and there are smaller numbers of species in Europe and Asia. They are not found, for some unknown reason, in the southern hemisphere. Most species are only a few inches long, although the largest species - the Japanese and Chinese giant salamanders - can reach over 1 metre in length.

Many amphibia are fully aquatic and often have greatly reduced legs. All urodeles Move slowly on land, but in water they are often efficient and elegant swimmers.

[edit] Meaning

The name Urodela is derived from Greek. The word can be divided into 2 parts. ' Ur ' & ' delos ' - Ur = tail; Delos = visible.
They have another name: Caudata. Caude means tail in Greek.
Finally The meaning of Urodela/Caudata is Animal with a body which is lizard like and has a distinct post-anal tail

[edit] Chararteristics

1. Two pairs of weak and equal limbs are present.
2. Skin is without exoskeleton.
3. Teeth are Present on both jaws.
4. Tympanum is present.
5. Eyelids may be present or absent
6. Gills are retained throughout (perinnibranchiates) the life. In some they are lost in the adults (caducibranchiates).
7. Well developed Lateral Line sense organs are present.
8. They show a transition of aquatic life to terrestrial mode of life.
9. Necturus like animals are completely aquatic, but some animals like Amphiuma are traditional forms losing gills but retaining gills slits, while Ambylostoma is a complete lung breathing form of adult condition.

[edit] 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.
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.

Necturus

Amphiuma

Tylotriton

Ambylostoma: 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 secertion 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.
Megalobatrachus: It is the gaint salamander of China and Japan and is the largest caudate known.
Tylototriton: It occurs in the eastern Himalayas region and is the only Indian caudate species.