Spiders Are Not As Old As We Thought

The oldest fossil spider was thought to be Attercopus fimbriunguis, which lived around 386 million years ago. But the scientists who discovered that fossil 20 years ago have found a few more in recent years and have now rethought their original conclusion. What they really found, they report this week in PNAS, was a proto-spider.

These proto-spiders didn’t have spinnerets, which modern spiders use to spin silk and weave a web, the researchers realized. Instead, the proto-spider could weave sheets of silk from modified hairs called spigots that sat on plates attached to its underside. The proto-spider also had a tail.

Though the proto-spider could produce silk, the researchers don’t think it could spin a web; the spigots weren’t flexible enough for this. Instead, they envision the creature using the silk to line burrows or maybe subdue prey. “We knew that it wasn’t used for making webs initially, for catching insects, because there were no flying insects when the earliest spiders were around,” the study’s lead author, University of Kansas paleontologist Paul Seldon, told BBC News.

So when did the earliest true spider live? They show up in the fossil record about 80 million years after the proto-spiders. And the two apparently co-existed for another 100 million years before proto-spiders went extinct.

Sarah Zielinski | | READ MORE

Sarah Zielinski is an award-winning science writer and editor. She is a contributing writer in science for Smithsonian.com and blogs at Wild Things, which appears on Science News.