Eight Blind Scorpions

Well, they're not all scorpions, but they're all blind. A quarry in Israel uncovered a cave which had apparently been sealed off for millions of years (or so the scientists say). The scientists found eight previously undiscovered species of invertebrates, some crustaceans and some scorpions.

But, since none of them had seen the light of day for millions of years, they have no eyes. Just another useless appendage that got ignored during breeding. Or maybe the blind ones coped better in the darkness than the sighted ones and thus had more children.

I bet if they start breeding these species in daylight, eventually sight would return. The code is in the DNA. It just needs to be retrieved.