Some odd-looking 50 million-year-old fossils fish discovered in the bowels of several European museums help explain how flatfish such as flounder, sole and halibut developed the strange but useful trait of having both eyes on one side. The trait, in which flatfish lie on their sides at the bottom of the sea, has posed a problem for evolutionary biologists because no one had found any so-called transitional fossils, until now.
“The important thing about this study is it delivers evidence of those intermediates,” said Matt Friedman of The Field Museum and the, Friedman examined specimens of two kinds of fossil fishes from the Eocene period in northern Italy. One was a new genus that Friedman named Heteronectes or “different swimmer.”What he found is that Amphistium, had been incorrectly assumed to have a symmetrical skull, but Friedman noticed that in some fossils, the eye was slightly out of place,and that one eye had begun migrating, but had not quite crossed the middle of the head.
The find raises the question of why this bizarre intermediate form developed. “It turns out they don’t lie flat and completely prone on the sea floor. They actually will prop themselves up slightly (with their fins),” Friedman said. Once in that position, having a slightly asymmetrical eye arrangement must have proved advantageous in the search for food.
Hat tip to Kathy Savage FCS Board Member