Marty’s photo of the day #3548: This excerpt from the Australia chapter in my first book, Cool Creatures, Hot Planet: Exploring the Seven Continents, explains the shot:

Earlier in this chapter, I promised to introduce you to a bizarre creature that would eliminate all reasonable doubts of evolution. I found such a creature—in fact, oodles of them—when I walked up a shallow stream that emptied into the ocean. I might not have noticed them if they weren’t jumping out of the water and climbing onto logs and fallen branches.

What were they? Mudskippers—a fish that spends more time out of water than in it. They breathe on land by absorbing oxygen through their moist skin, they propel themselves by using their fins as legs, and since fish don’t have eyelids, they keep their eyeballs moist by periodically retracting them into their sockets. These unique adaptations give mudskippers the ability to remain on land for a day or more.

The six-inch-long fish were comical in appearance. They had bright-blue protuberant eyes atop their heads, pointed tails, and golden bodies with blotchy dark-brown bands.

What do mudskippers have to do with evolution? They’re a species in transition—evolving from fish to terrestrial animal. If we could sit by the stream for thousands of years, we could watch them change. Hmmm, what if in addition to developing legs, their eyes grew even farther out of their heads? Then, they’d look like little extraterrestrial animals.