This 300 Million Year Old Fossil Could Explain What The Deal Is With Spiders

It won’t hearten arachnophobes to learn that scientists don’t actually know a great deal about where modern day spiders come from - but all that could be about to change thanks to a new fossil unearthed in France.

The 305-million-year-old arachnid fossil was handily preserved in 3D, which is giving researchers unprecedented insight into early spiders’ anatomical details.

It’s a new species of arachnid, and has been named Idmonarachne Brasieri in honour of University of Oxford Professor Martin Brasier, who passed away in 2014.

Details of the origins of spiders remain limited, with little knowledge of their predecessors and no insights into character acquisition early in their evolution, including where their ability to spin silk and make webs comes from.

This new fossil, which isn’t a true spider but an uraraneid, could hold the answers.

Researchers from Manchester University, Berlin’s Museum für Naturkunde, the University of Kansas and Imperial College London have worked with the Natural History Museum and the UK’s Diamond Light Source to scan and examine the fossil.

Lead author Doctor Russell Garwood, of Manchester University, said: “Our new fossil occupies a key position in the evolution of spiders.

"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.

"We have known since 2008 that a group called the uraraneids were a sister group to true spiders - they could make silk, but probably laid it down in sheets, rather than spinning it as modern spiders do.

"They also had a tail-like structure at the end called a flagellum. Analysis of Idmonarachne brasieri suggests that as the spider lineage evolved, the animals lost their tail-like structure, and developed spider-like fangs and limbs.

"Whilst they could likely make silk, the ancestors lacked the ability to spin it using specialised appendages called spinnerets. These are the features that define true spiders, and give them more control over the use and distribution of silk."

He added: "This is part of an ongoing effort to look at early arachnids, and see what this can tell us about the early evolution of the group, how they came onto land and what their evolutionary tree looks like.

"Arachnids as a whole are a very diverse group, but working out how they are all related to each other has proved a challenge.”