Neatorama and Rue The Day have an in-depth two-part series covering the most amazing cave-dwelling creatures, including the olm (pictured).

The olm was the first exclusively cave-dwelling animal to be discovered, but that's not what people thought it was at first—they thought it was a baby dragon that was washed up from the underground realm of the dragons.

Learn more about these pigmentless, eyeless critters and other oddly adapted animals by reading both articles.

[Image courtesy of Wikipedia user Arne Hodalic]