Researchers have discovered a remarkable ancient arachnid species, resembling a spider with a tail, preserved in a 100-million-year-old amber found in Myanmar.
Also, scientists aren't sure if it's poisonous because their fangs are not large enough to examine.
The creatures were tiny, with a body length of about two-tenths of an inch, including the tail.
While creeping through the dinosaur-era forest, four spiders became enveloped in a pool of tree resin oozing from conifer trees.
Scientists say it's possible that the creatures are still scuttling through the forests of Myanmar, where the specimen was discovered.
One thing the team doesn't know is what the tail would have been used for or if the spider was venomous.
The finding is described in a paper appearing in Nature Ecology & Evolution by an global team including Paul Selden of the Paleontological Institute and Department of Geology at the University of Kansas and colleagues from China, Germany, Virginia and the United Kingdom.
Dr. Ricardo Perez-De-La Fuente, of the Oxford Museum of Natural History, said that the incredible fossils will play an important role in deciphering the puzzle of the evolution of spiders and allied groups.
The foursome were entombed in stunning detail - the head, fangs, male pedipalps, four walking legs and silk-producing spinnerets at the rear could all be observed.
Named Chimerarachne after the mythological Chimera - a hybrid made up of several animals - it is believed the spider's tail would have been used for sensory purposes much like an antenna.
Selden also noted that increased production of amber in northern Myanmar gave the team a great hint as to where they might potentially find more prehistoric creatures.
Spiders as a group date back to more than 300 million years ago.
Co-author of the study, Russell Garwood of The University of Manchester, said that they had known for decades that spiders evolved from arachnids that had tails, more than 315 million years ago.
The specimens had spinnerets, or silk-spinning organs, jutting from the bottom of their abdomens - a feature they share with modern-day spiders. If they live in burrows and leave, they leave a trail so they can find their way back. "Like all spiders it would have been a carnivore and would have eaten insects, I imagine".
An abstract of the study says the "new fossil most likely represents the earliest branch of the Araneae, and implies that there was a lineage of tailed spiders that presumably originated in the Palaeozoic and survived at least into the Cretaceous of Southeast Asia". Vinegaroons, or "whip scorpions", are close living relatives of spiders that sport tails, and the same research team has previously discovered older arachnids with tails but no spinnerets. But what makes the fossil so unique, and different to spiders of today, is the fact it has a tail.
They look like these older creatures so it's rather a surprise to see them alongside spiders, he said of the insects found alongside the fossils.