Axolotl

Pronounced Axe-oh-lot-ul, this salamander is native to only one small are of Mexico, Lake Xochimilco. Axolotl's differentiate themselves from other salamanders in that they retain their tadpole-like characteristics throughout their entire lives, specifically the external gills and tail.

Axolotl's are almost extinct in the wild, because, like the previously featured Texas Blind Salamander, their habitat is being threatened. Due to their natural homes being right next to Mexico City, the 2nd most populated city in the world, their watery homes are being used up and polluted. Interestingly though, they are used extensively for scientific research, and are kept as pets in multiple countries, ensuring that the species won't ever become truly extinct for a very long time, if ever.

Image from Wikimedia Commons

Now, just why exactly are Axolotls being used for research? Because they can completely regrow their limbs! Unlike most creatures, who just have to deal with an arm being chomped off, the Axolotl can completely regrow it over time. They are also able to easily retrieve transplants from other specimens and receive full functionality from them. There is also documentation of them regrowing their vital organs, brain segments and spinal chord.

Also previously mentioned was their existence as household pets. I am no expert on their captivity requirements, so I'll just redirect to curious to Axolotl.org, which seems to know what they are talking about.