Tailed spider trapped in 100-million-year old amber offers insight in evolution

A spider-like creature bearing a long tail has been discovered in an amber from Myanmar dating back about 100 million years.

"There's been a lot of amber being produced from northern Myanmar and its interest stepped up about ten years ago when it was discovered this amber was mid-Cretaceous," said Paul Selden, a palaeontologist at the University of Kansas and an author of a paper on the ancient arachnid.

"Therefore, all the insects found in it were much older than first thought," Selden told the university in an interview.

The finding is published Monday in a paper in Nature Ecology & Evolution by an international team of researchers from the United States, China, Germany and the United Kingdom.

According to the paper, the creature shares many similarities with modern spiders including fangs, eight legs and silk-producing spinners.

Moreover, it also bears a long flagellum, or a tail, at its rear, which is not commonly seen among modern spiders.

Thought the ancient arachnid has a tiny body, only about 2.5 millimeters long, it had a tail nearly twice of its body length.

"Any sort of flagelliform appendage tends to be like an antenna," Selden said, "It's for sensing the environment. Animals that have a long whippy tail tend to have it for sensory purposes."

The tailed arachnid, named Chimerarachne after the Greek mythological Chimera, documents a key transition stage in spider evolution.

Previously, Selden and his colleagues had found similar insects without spinnerets from the much older Devonian and Permian periods.

"That's why the new one is really interesting, apart from the fact that it's much younger -- it seems to be an intermediate form," Selden said.

"In our analysis, it comes out sort of in between the older one that hadn't developed the spinneret and modern spider that has lost the tail," he added.