Paleontologists working in South Korea found ancient spider fossils with still-glittering eyes.

Spider fossils are rare, the researchers wrote in a paper published online Jan. 28 in the Journal of Systematic Paleontology. Their bodies are so soft that they typically decay entirely soon after death, leaving no trace unless they happen to end up trapped in amber. But 11 spiders from the Cretaceous period have turned up preserved in shale on the Korean Peninsula. And two of the fossils included the still-shiny traces of sparkling eyes.

Those glittering bits are mirror structures in the eyes called tapetums that bounce light from the back of the eye back through the retina. Animals use them to improve their night vision, usually at the expense of some overall blurriness. Wolf Spiders have large mirrors in their eyes.