Expert: Walter Hintz - 8/28/2011

Question
Hello, and thank you for being willing to answer questions. I hope that you are doing well, and I also hope that you are not annoyed by questions that are hypothetical.

In a certain science fiction franchise, there is shown an intelligent, bipedal haplo-diploid amphibian species -- they have  binocular vision, and two forward-facing eyes the size of billiard balls, which (as one would expect) have nictitating membranes. I have also noticed that they have cartilaginous "horns" (probably for camouflage). Interestingly, unlike our frogs, they have a real set of teeth rather than just vomeral teeth.

What is REALLY odd to me, and the thing I would like to have your opinion on, is that in blinking the eyes shut, their eyelids blink upward to close -- closure causes the edge of the eyelid to travel upward, not downward as in humans.

Can you even guess how this trait might have evolved? I do not know of any real creatures that have this trait. I would have guessed that it had something to do with a different surface gravity, except they evolved on a planet with surface gravity close to 1G, similar to ourselves.

Thanks very much for your time!

Answer
Hi Julian
First of all let me assure that hypothetical questions do not annoy me. I have been plagued recently by someone who keeps asking about the best way to kill yourself.
  As to your question here fantasy and science fiction allows us to visualize a creature with just about any features we want without consideration of natural selection. Considering this mythical amphibian I can only assume that the upward eyelids had some survival value. I do not think gravity is involved with the development of eyelids.