Fossils of fish with one eye atop its head and another on its side that is most likely an ancestor of modern flat fish -- such as sole, flounder and halibut -- were unearthed more than 200 years ago, but have just recently been brought to light.
The 50 million-year-old fossils had been dug up many generations ago in limestone quarries in northern Italy and near Paris. Researcher Matt Friedman of the Field Museum in Chicago recently found them in museums in England, France, Italy and Austria.
"They were first figured in a publication over 200 years ago," Friedman told LiveScience. "So they have been floating around for some time now, but everyone said, 'Oh, they're symmetrical.'"
Upon closer examination, Friedman found the fish are not symmetrical. Most notably, the eye orbits seem to be mid-migration. The lopsided lookers probably helped the seafloor-hugging predator to peer upwards for passing prey.
"What we found was an intermediate stage between living flatfishes and the arrangement found in other fishes," said Friedman. These fossil fishes "indicate that the evolution of the profound cranial asymmetry of extant flatfishes was gradual in nature."
The finding, detailed in the July 10 issue of the journal Nature, refutes creationists’claims that flatfish could not have evolved gradually, Friedman said.
"The important point is that many evolutionary biologists also could not imagine how the flatfish body plan could have arisen gradually, via a series of intermediates," Friedman said.
The story "peddled for flatfishes," Friedman said, is that "they arose in a single generation, following the birth of a deformed 'hopeful monster' with both eyes on one side of the skull." The "hopeful monster" refers to the idea that some genetic mutations could give rise to a deformed "freak" that is usually at a disadvantage but every so often the oddball makes sense functionally.