Fossil hunters in Korea discovered long-lived spiders preserved in rock. And to the joy of the researchers, the eyes of the arachnids are still reflective – about 110 million years after the creatures died.
It is rare for insects and arachnids – which are far more brittle than bald sea creatures – to become fossil in stone. But for reasons not yet known, a couple of these spiders were fossilized, and the unique shape of their eye structures continues to reflect the light – even in their petrified form.
The reflective eye structure is called a tapetum, and it is often used by creatures that hunt in the dark.
"Some hunters have a tendency to use this different kind of eye," said Paul Selden, director of the Paleontological Institute at Kansas University's Biodiversity Institute and the Natural History Museum. "This was the first time a tapetum had been found fossil. This tapetum was canoeed ̵
Today's wolf spiders use the same eye structures to hunt, Selden added.
There is still a mystery: How did the spiders become fossilized? Their petrified organs are found in a layer of rocks filled with fish and other marine crops – but spiders do not live in water.
"It must be a very special situation where they were washed in a body of water," Selden said. "Normally, they would float, but here they sank, and it kept them away from decaying bacteria – it could have been a low-oxygen state."
Seldom and his Korean colleagues – who actually discovered the old spiders – now have to mention the curious fossils. They were found only because Korean countries are often excavated, so scientists at the fossil curious dig in to see which old news is hidden in the earth's crust.
"Then they cut the hillside to make a flat area and there are temporary excavations as they cut away and build a factory or whatever – this was where they found these fossils, "said Selden.