China Daily Global Edition (USA)
Ancient spider with a tail found in amber
WASHINGTON — If you are not a fan of spiders, you may not like the creepy little arachnid scientists found entombed in chunks of amber from northern Myanmar. Unlike its spider cousins alive today, this guy had a tail.
Scientists on Monday described four specimens of the arachnid, called Chimerarachne yingi, that inhabited a Cretaceous Period tropical forest about 100 million years ago during the dinosaur age. Alongside modern spider traits such as a silk-producing structure called a spinneret, it possessed a remarkably primitive feature: a whip-like tail covered in short hairs that it may have used for sensing predators and prey.
“It is a key fossil for understanding spider origins,” said paleontologist Bo Wang of the Chinese Academy of Sciences. “Our new fossil most likely represents the earliest branch of spiders, and implies that there was a lineage of tailed spiders that presumably originated in the Paleozoic (the geological era that ended 251 million years ago) and survived at least into the Cretaceous of Southeast Asia.”
Despite its fearsome appearance, the fanged Chimerarachne was only about three-tenths of an inch (7.5 mm) long, more than half of which was its tail.
University of Kansas paleontologist Paul Selden said Chimerarachne represents “a kind of missing link” between true spiders and earlier spider forerunners that had tails but lacked spinnerets.
“Chimerarachne could be considered as a spider. It all depends on where we decide to draw the line,” Selden said. “I am sure arachnophobes would not like this animal, except that it is only a few millimeters long, so it would be living almost unseen by them.”
Venom glands
The earliest arachnids, a group including spiders, scorpions, mites, ticks and others, dates to about 420 million years ago. The oldest-known true spiders lived about 315 millions year ago.
“Spinnerets are used to produce silk for a whole host of reasons: to wrap eggs, to make burrows, to make sleeping hammocks, or just to leave behind trails,” said Paul Selden, Wang’s co-author and a professor at the University of Kansas.
Chimerarachne also boasts pincerlike appendages, called pedipalps, used to transfer sperm to the female during mating, a signature trait of all living spiders.
Its whip-like tail or flagellum, also known as a telson, likely “served a sensory purpose,” Wang said.
By contrast, modern spiders use silk spun into webs to monitor changes in their surroundings.
They also have venom secreted from special-purpose glands, but neither of the studies was able to confirm that Chimerarachne could poison its prey.
The new species was discovered in the jungles of Myanmar, which yields nearly 10 tonnes of amber every year.
“Spiders have soft bodies and no bones, so they don’t fossilize very well, so we rely on special conditions — especially amber — to find them,” Wang explained.