Very Old Gold Silk

April 22, 2011

Tags: Nephila, Selden

Nephila spiders are big, they're bold (in terms of web coloration, that is), and now we know they're old, too--more than 165 million years old, the approximate age of a fossil just described as a Nephila by veteran spider fossil researcher Paul Selden and colleagues ChungKun Shih and Dong Ren. These gorgeous spiders are also known as the golden orb weavers because their huge webs range in color from pale yellow to vibrant gold. We write about why spiders would have evolved to construct such obvious webs--and why insects still fly into them--in Spider Silk's tenth chapter, "Now You See It, Now You Don't."

Named Nephila jurassica in honor of its age, this fossil is the oldest Nephila fossil yet found and hails from a site in present-day Inner Mongolia that has already yielded exciting numbers of arthropod fossils and may contain more spider bounty. It's startling to consider that, as far as spiders have been concerned, the dinosaurs were interlopers who showed up and then disappeared rather quickly.

Here's how to think about N. jurassica in the history of spiders: The oldest spider fossil (a mesothele) yet found is 290 million years old, or 130 million years older than N. jurassica. The oldest araneomorph fossils are 225 million years old, or 60 million years older. And the oldest known fossil of an araneoid--the group containing all vertical-orb weavers, including Nephila, and spiders evolved from vertical-orb weavers--is about 175 million years old, or about 10 million years older. We can't tell from this fossil whether Nephila jurassica wove golden webs, but its size certainly indicates that, like today's Nephila, it wove giant webs and could wrangle with large insects. Arthropods don't fossilize easily. So every new spider fossil is a treasured key to the distant past.




Tags

"...a compelling introduction to evolution in action through the lens of spiders and their silks."

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