YE MIGRATION
More than 500 species of flatfishes live in fresh and salt water. They are born with eyes in the normal spot, but one eye gradually migrates to the other side of the head.
“Every flatfish is born symmetrical before it becomes a perversely asymmetrical adult,” Friedman said.
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.”
“It is a fossil I found unloved in a museum drawer in Vienna covered with about a century of industrial-era soot.”
The other fossil, Amphistium, has been incorrectly assumed to have a symmetrical skull, but Friedman noticed that in some fossils, the eye was slightly out of place.
That inspired him to use computed tomography or CT scans to get a better look at the skulls of these fossils.
What he found is that one eye had begun migrating, but had not quite crossed the middle of the head.
“It’s not quite in the Cyclops position,” Friedman said.
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, he said.
But Friedman cautioned about making too many inferences.
“Our inability to imagine is what got us into this predicament,” he said, referring to the whole flatfish debate.
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