Spiders with tails discovered in Burma

Recently, miners in northern Burma pulled this ancient amber out of a quarry. Chunks of it were purchased by paleontologists, who found in the amber many well-preserved spiders — some of them with long, almost scorpion-like tails. Yes, tails.

Around 100 million years ago, oozing tree sap poured over hundreds of tiny spiders, killing and preserving the critters in hardened amber. 

After closely scrutinizing the critters, scientists have determined they're likely a sort of proto-spider, not quite a proper arachnid, but a bridge between today's eight-legged insect-hunters and a more primitive species.

"It’s kind of a missing link," said Paul Selden, director of the Institute of Paleontology at the University of Kansas and co-author of the study, in an interview. The research was published Feb. 5 in the journal Nature Ecology and Evolution. 

Although Selden doesn't think these creatures are quite spiders, he acknowledges they certainly share many arachnid-like characteristics. 

"It's difficult to draw the line," he noted.

These early arachnids, scientifically classified as Chimerarachne yingi, contain the spinneret organs that modern spiders use to create their spectacular, varied, and complex aerial webs. But the presence of the whip-like tail — longer than the creatures' themselves — was a bit too much for Selden and his team to bundle into the arachnid family.

Another group researchers concluded that these tailed-spiders should be lumped in with a group of more primitive, now extinct spiders.

But Selden said these differences in evolutionary placement are pretty insignificant. 

A close-up of the tip of a protospider's tail.

"Essentially, we’re in agreement with where it sits," he noted.

Regardless of where the critters lie on our fickle evolutionary tables, modern spiders apparently didn't need these hairy tails to become the immensely widespread creatures we know them as. Today, there are more 47,000 known species of spiders. 

An image of one of the preserved specimens, frozen in amber.

The tailed spiders probably used their elongated appendages as a sort of sensing device, said Selden. Today's spiders can sense the environment in a multitude of ways, such feeling vibrations on their webs. 

Although the spiders that commonly dangle in our homes and gardens have no tails, that doesn't necessarily mean that their tailed evolutionary cousins are, in fact, extinct. 

These critters are small — around 2.5 millimeters in size — and could be crawling behind the bark of a tree.