A half-billion-year-old fossil "compound" eye (left)—likely from an ancient shrimplike predator—was surprisingly advanced for its time and gave its owner vision comparable to those of modern insects, such as the robber fly (right), a new study says.
Unlike human eyes, which have only one lens, the compound eyes of arthropods—including insects and crustaceans—have hundreds or even thousands of separate lenses.
"The owner of a compound eye sees the world as a series of dots. Each dot is generated by one lens in the eye, so the more lenses you have, the more detail you see the world with," explained Michael Lee, an evolutionary biologist at Australia's University of Adelaide.
"If you have very few lenses, you're going to see the world with very few dots—everything will look like very bad newsprint."
The research by Lee and his team was detailed in the June 30 issue of the journal Nature.
As seen in this 3-D digital reconstruction, the lenses in the center of the newly discovered fossil eye are slightly larger than those at the periphery—a design that allows modern insect predators to see in dim environments.
"This guy was probably able to hunt at twilight or in deeper waters," García-Bellido said.
The new fossil eyes were found in isolation, and their owner remains a mystery. One likely candidate is a bizarre-looking creature known as Tuzoia, which resembled "a shrimp inside a clam," the University of Adelaide's Lee said.
A detail of a photograph of one of the new fossil eyes reveals some of the 3,000 lenses that allowed its owner to see the world in remarkable clarity.
While this creature would have had relatively sharp vision, it's not known whether it could see in color like some modern insects, such as bees and dragonflies.
"The eyes in modern arthropods have lenses on top and several pigmented cells underneath," which allow them to see in color, the Spanish National Research Council's García-Bellido said.
"What we have of the fossil eye is just the top surface. We don't have any information about the number of cells that were beneath it, the size of those cells, or how those cells were connected to each other."