Spider relatives that are almost three and four times as old as C. yingi also had tails but no spinnerets.
Commenting on the research, Dr Ricardo Perez-De-La Fuente, of the Oxford Museum of Natural History, said the "amazing fossils" will be important in deciphering the puzzle of the evolution of spiders and allied groups.
Another view of the holotype of C. yingi as it was preserved in amber for 100 million years...coincidentally the same number of nightmares today's announcement will foster. But the main difference is, arachnids had a tail while modern-day spiders do not have any tail. The research was conducted by a team which included researchers from the University of Kansas and colleagues from different nations like China, Germany, Virginia and the United Kingdom.
The tiny animal was trapped in amber, ie petrified resin, so it probably lived under a tree with resin. What's incredible is that the amber process preserves parts that wouldn't be conserved through regular fossilization. However, even though scientists have spent many years studying bugs living in amber, only recently they were able to get its true age.
The new study confirms a prediction the researchers made a few years ago when they described a similar arachnid that also resembles a spider with a tail, but does not have silk-producing organs - known as spinnerets.
This is then offered for sale to various institutions, with the new species - dating back to the mid-Cretaceous period - coming to light when specimens were made available to the Nanjing Institute of Geology and Palaeontology.
It had eight legs and fangs, typical of most modern spiders, and measured about 2.5 millimeters long, with a tail extending to 3 millimeters long - something that no modern spider is equipped with.
"We don't know if it wove webs", said the KU researcher. And like modern spiders (the Araneae), C. yingi males had two modified appendages called pedipalps near the head which were used to inseminate females. "It was a pretty good tropical rainforest, and there are a great many other arachnids we know were there, particularly spiders, that are very similar to the ones you find today in the southeast Asian rainforest". Another distinctive feature is that uraraneids had plates on their bellies instead of the squishy abdomens seen in spiders. Their bodies are close to one-tenth of an inch long but their tails more than double their length.
© The ancient arachnid likely used its tail as an antenna. (Unlike modern day spiders, uraraneids had plated bellies and silk-spinning organs on the edges of their plates, rather than near their rear end).
Those with arachnophobia might want to look away now, as scientists have unearthed an incredible 100m-year-old spider that actually had a tail. Scientists may have just discovered your worst nightmare. It's unknown if the proto-spiders were venomous or not, but zoologist Gonzalo Giribet says they likely wouldn't be harmful to people.
The Cretaceous spider Chimerarachne yingi, found preserved in amber, lived about 100 million years ago and had some unusual features, including a long, whiplike tail.