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305 million year-old ancestor of spiders is identified

April 28, 2016 Leave a comment
Early arachnid

Idmonarachne brasieri lived about 305 million years ago. Image courtesy University of Manchester.

Paleontologists have identified an ancestor of modern spiders that lived before the dinosaurs began their long domination of the planet.

The arachnid’s fossil remains were found during the mid-1970s in Europe embedded in an iron-rich mineral, siderite, that is difficult for x-rays to penetrate. Researchers used a synchotron, which emits more powerful x-rays, to identify the organism.

Named Idmonarachne brasieri, the organism was likely a member of a group of arachnids called uraraneids. These animals lacked spinarets, which modern spiders use to spin webs, and instead would have discharged silk in sheets.

“Our new fossil occupies a key position in the evolution of spiders,” Dr. Russell Garwood of the University of Manchester, the lead author of a paper documenting the discovery, said. “It isn’t a true spider, but has given us new information regarding the order in which the bits of the anatomy we associate with spiders appeared as the group evolved.”

Scientists know little of the origin of spiders and the evolutionary path by which such anatomical features as spinarets formed is not well understood.

The paper appears in the March 30 edition of Proceedings of the Royal Society B.

 

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