Cave salamander

The olm (Proteus anguinus) of the western Balkan Peninsula.

A cave salamander is a type of salamander that primarily or exclusively inhabits caves, a group that includes several species. Some of these animals have developed special, even extreme, adaptations to their subterranean environments. Some species have only rudimentary (or even absent) eyes (blind salamanders). Others lack pigmentation, rendering them a pale yellowish or pinkish color (e.g., Eurycea rathbuni).

With the notable exception of the olm (Proteus anguinus), all "cave salamanders" are members of the family Plethodontidae ("lungless salamanders"). Almost all of them are paedomorphic and therefore never undergo metamorphosis, but it is not clear if this happened before or after they adapted to an existence in caves, as some species that don't live in caves are also paedomorphic.[1][2]