"It must have lived for about 200 million years side-by-side with spiders, but we've never found a fossil of one of these [before] that's younger than 295 million years", said Dr Garwood, from Manchester's School of Earth and Environmental Sciences. Mesothelae spiders are only found in China, Japan, and Southeast Asia today.
Around 15 years ago they discovered that Burmese amber was older, which resulted in a huge amount of new material becoming available for study.
Believed to have existed during the Cretaceous age approximately 100m years ago, the new spider species appeared relatively normal at first by modern standards, with fangs, four walking legs and silk-producing spinnerets at its rear.
Paul Selden, a palaeontologist who worked on the specimen at the University of Kansas told The Guardian that they were "a kind of missing link" between the two species - the uraraneids and primitive living spiders.
Scientists believe the tail was longer that its body and was used as a sensory device to seek out prey or escape predators. A new, freaky spider-like creature has just been discovered in Southeast Asia, having been encased in amber during the Cretaceous period some 100 million years ago, and it might be more terrifying than any of the creepy-crawlies lurking in the dark corners of your basement. But experts disagree about how these fossils relate to modern-day spiders, because there's something unusual about their crumpled corpses: all four of them have tails. On the basis of the creature's tail, they conclude that it belongs to the Uraraneida, a group of spider relatives that was thought to have gone extinct around 275 million years ago.
However, the 100 million-year-old spider fossils could change some of the theories regarding the evolution of the spiders.
Arachnids are a group of eight-legged invertebrates that includes scorpions, ticks, and spiders. The tail lends it an exotic look that spider-fearing folk will likely find unsettling.
Palestinian man shot dead by Israeli forces
The anti-settlement Peace Now group said the move to legalise the settlement is a "cynical exploitation of the murder". Israel has imposed severe restrictions on Palestinian development in this area, home to dozens of Israeli settlements.
They introduced their discovery, dubbed Chimerarachne yingi, in a pair of papers published Monday in the journal Nature Ecology and Evolution.
Specimens belonging to the newly identified species called Chimerarachne yingi were collected from the amber markets of Myanmar, where paleontologists have time and time again come across invaluable fossils.
An artist's concept drawing shows Chimerarachne.
"And now suddenly we have another group that is not a spider that also has those characteristics", Giribet said.
Bottom right: The entire specimen in dorsal ventral view.
But the team describing the holotype of C. yingi places it within the arachnid family tree as an early true spider, citing the presence of both those well developed spinnerets and modified male pedipalps which assist with sperm transfer.
No living species of spider has a tail but Mr Selden said the arachnid's remote habitat made it possible that tailed descendants may still be alive in Myanmar's backcountry to this day. Some argue that spinnerets were the key innovation that allowed spiders to become so successful; there are almost 50,000 known spider species alive today.