Typically when scientists find a fossil, the fossil is the remains of creatures that have bones. Finding fossils of soft-bodied creatures such as spiders is unusual. The typical discovery of a spider comes in amber.
A paper co-written by a scientist from the University of Kansas has described fossilized spiders that were discovered in an area of Korean shale called the Lower Cretaceous Jinju Formation. Even rarer than finding the fossilized remains of a spider is that the fossils are so well preserved that the eyes of the spiders still reflected light.
The remains are of two spiders are from the extinct spider family Lagonomegopidae that were known to have reflecting eyes to enable night hunting. The two fossils were preserved in “strange silvery flecks” on dark rocks. Researcher Paul Selden says that the fossil spiders had large eyes brightly marked with crescentic features.
Selden says that he realized that the eye structure must have been the tapetum, which is a reflective structure in an inverted eye that allows light to come in and revert back to retina cells. The scientist says that modern spiders have eyes with a tapetum. The new paper is the first to describe such a feature in a fossilized spider.
Selden says that the eye structure of the fossil spiders helps scientists to place the group among other spider families. The discovery of the new spider fossils boosts the number of known spiders from the Jinju Formation from one to 11. The team says the excellent preservation of the spiders suggests they were somehow protected from deterioration. The team believes the spiders sunk somehow into the ancient lake rather than floating as is normal, preventing degradation.