A shrimplike superpredator of the ancient seas may have had more than 30,000 lenses in each eye, granting the animal enhanced vision that would have rivaled or exceeded that of living insects and crustaceans, a new study says.
The finding is based on a pair of 515-million-year-old stalked eyes belonging to the meter-long (three-foot-long) Anomalocaris, whose Latin name translates roughly to "weird crustacean."
Unlike humans—whose eyes each have a single, large lens—insects and crustaceans have eyes with multiple, usually hexagonal lenses, each of which transfers separate bits of information to the brain.
When study co-author Diego C. García-Bellido and colleagues began counting Anomalocaris's fossilized lenses under a microscope, they could scarcely believe their eyes.
"We're talking 16,000 lenses on half an eye," said García-Bellido, a paleontologist at the Spanish Research Council in Madrid.
"Wow—that was the most mind-blowing aspect of it all."
The other side of the pair of Anomalocaris eyes is embedded in rock and can't be studied, García-Bellido said, but it's possible both sides had equal amounts of lenses.
"Great White Shark" of Its Time?
The largest animal of the Cambrian period (542 to 501 million years ago), Anomalocaris had a circular, plated mouth with teeth-like serrations and spiny arms for grasping prey such as trilobites, a type of extinct arthropod.
At the Kangaroo Island site, scientists also found Anomalocaris coprolites—or fossilized poop—in the shale deposits. (Read more about fossil feces.)
"It's quite incredible—you find bits of pieces of trilobites in it," said García-Bellido, whose team has received funding for future work from the National Geographic Society's Committee for Research and Exploration. (The Society owns National Geographic News.)
The new study offers more proof that the creature was the superpredator of its era—"probably the great white shark of the Cambrian ocean," García-Bellido said.
Anomalocaris and its relatives were so successful, in fact, that they lasted for another 40 million years until likely being outcompeted by fish.
The ancient "shrimp" eyes are described in last week's issue of the journal Nature.