Ancient arachnid had similar legs and jaw to spiders but
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Published: 14:11 GMT, 30 March 2016 | Updated: 14:38 GMT, 30 March 2016
Spiders predate the dinosaurs, scurrying along 315 million years ago - but their precise origins remain a mystery.
Now scientists believe they have filled a 'gap' in the evolutionary story of arachnids, with the discovery of a fossil that's the closest relative to spiders ever discovered.
The creature, dubbed Idmonarachne brasieri, measured less than one inch long (1.5cm) and lived alongside the oldest known ancestors of modern spiders 305 million years ago.
Idmonarachne brasieri measured less than one inch long (1.5cm) and lived alongside the oldest known ancestors of modern spiders 305 million years ago. The species of prehistoric arachnid (pictured) was reconstructed using CT scans and high powered x-rays
It is hoped the specimen will help scientists understand more about the early origins of modern-day spiders.
The fossil was collected years ago in Montceau les-Mines, eastern France, but has only just revealed its creepy secret, since the first part of its body was encased in rock.
Now, researchers from The University of Manchester, Berlin's Museum für Naturkunde, the University of Kansas and Imperial College London have worked with the Natural History Museum and the Diamond Light Source in Oxfordshire to reconstruct the prehistoric arachnid's body using CT scans and high powered x-rays.
They were able to do this because the fossil was preserved in 3D, enabling the researchers to investigate its minute anatomical details.
The fossil was collected years ago, but has only just revealed its creepy secret, since the first part of its body was encased in rock. Slices of the fossil are shown above
The fossil was re-discovered in a box full of rocks at the University of Kansas, having originally been collected In Montceau les-Mines, a rich region of fossil-bearing deposits in eastern France (marked on the map)
THE EVOLUTION OF SPIDER SILK
Scientists have known since 2008 that a sister group to true spiders, called the uraraneids, could make silk.
However, they 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 I.brasieri suggests that as the spider lineage evolved, the animals lost their tail-like structure and developed spider-like fangs and limbs instead.
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.
The fossil was re-discovered in a box full of rocks at the University of Kansas, having originally been collected from a rich region of fossil-bearing deposits.
Russell Garwood from the University of Manchester, first author of the study which was published in the journal Proceedings of the Royal Society B, told MailOnline: 'This animal is the closest thing we have to spiders without being a true spider, so it sits in a key position when looking at the evolution of the group.'
Not much is known about the origins of spiders with little knowledge of their predecessors or how they came to get their scariest features.
As well as the ancient archanid's eight legs, the team spotted it has strong jaws, showing it is a distinct species and not another distant cousin of spiders from the same time, the BBC reported.
They also noticed it lacks the tail-like appendage, or flagellum, of an older extinct arachnid family including Attercopus, which lived 80 million years earlier.
These earlier creatures didn't have spinnerets, which allow modern spiders to weave their webs, so I.brasieri fills an evolutionary gap because it has spider-like features such as legs and jaws, but no spinnerets.
Dr Garwood explained: 'I.brasieri shows us that spider-like ancestors lost a tail, which older, closely related animals called Uraraneids had and developed spider-like limbs and mouthparts, but that the key innovation which defines spiders is their spinnerets.'
I.brasieri fills an evolutionary gap because it has spider-like features such as legs and jaws, but no spinnerets (shown) which modern spiders such as this orb-weaver (stock image) use to produce 'ropes' of silk
'These are small structures on the underside of the animal that help them control silk.'
He added that I.brasieri probably split off the spider line after Attercopus, but before modern spiders appeared.
The earliest known spider fossil was found in the same mineral deposit and has spinnerets.
'So what we're actually looking at is an extinct lineage that split off the spider line some time before 305 million years ago, and those two have evolved in parallel,' he 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.'
Dr Garwood said the innovation of spinnerets may be what makes spiders so ubiquitous.
There are more than 45,000 known species - compared to a little over 4500 for mammals, for example - which makes them among the most successful arachnids,' he said.
'This success also makes studying their origins and early evolution - both things about which we have relatively little information - a really rewarding thing to do.'
The new species is named Idmonarachne brasieri in honour of Professor Martin Brasier of the University of Oxford, who passed away in December 2014.
Ancient arachnid had similar legs and jaw to spiders but Boeing 'Starliner' Test Article Literally Coming Together