X-Ray Fish – Small fish that can be usually found in the Amazon River.
The only two animals I know of that begin with the letter X are Xenopus laevis (a type of frog) and Xenoturbella (a type of worm).
Xenopus Laevis is commonly known as the African clawed frog, but it can also be found in Texas and Guatemala.
Xenopus is a genus of amphibian in the family Pipidae. It has ten described species and sometimes collectively with its sister group Africa pipids (Hylidae), it forms a sub-group called “African clawed frogs”. The generic name may be derived from the word xenos for “stranger” or “foreigner”, appropriate for inhabitants of unfamiliar lands. Fossils dating to the African Pluvial Phase of Pleistocene South America indicate that Xenopus originated south of the equator in ancient wetlands within sight of Antarctica, then spread north as climates warmed from marine isotopic stage four through what would become stages five and six until they reached their present distribution