The Cretaceous-era arachnid had the front end of a
spider and a scorpionlike tail appendage, but more specimens
are required to find its place on the evolutionary tree.
Credit Bo Wang
It’s the stuff of prehistoric nightmares.
Eight legs. Fangs. And a whip-like tail.
Call it Chimerarachne yingi, a newly discovered arachnid that crawled around rain forests in what is now Southeast Asia more than 100 million years ago during the Cretaceous period. Its remains were found imprisoned in amber, as if Mother Nature herself tried to lock this tiny terror away from the rest of the world.
Two different teams of researchers discovered four specimens of the new species in the amber markets of Myanmar. Their findings were published in two separate papers on Monday in the journal Nature Ecology & Evolution.
“The material is stunning in the quality of its preservation,” said Greg Edgecombe, an invertebrate paleobiologist at the Natural History Museum in London, who was not involved in the study. “It throws up a combination of characters that initially seems alien to an arachnologist.”
C. yingi is not a spider, but rather a relative that lived alongside ancient spiders for millions of years. Its discovery provides insight into the evolutionary history of the creepy crawlers that have spun webs around the planet.
Similar to today’s black widows and huntsman spiders, C. yingi had silk-producing spinnerets near its rear end. The males of this species also had two modified appendages called pedipalps near their heads that were used like syringes to deliver sperm to females. But unlike today’s spiders, C. yingi had a long tail, like those seen in whip-scorpions or vinegarroons.
“Take the front of a spider, the end of a vinegarroon and then you put spinnerets on it and that’s our fossil,” said Gonzalo Giribet, an invertebrate biologist from Harvard University and an author on one of the papers.
Though the arachnid was quite small, only about 2.5 millimeters long, it had a tail nearly twice its body size. The tail, or telson, was most likely a sensory organ rather than an acid-flinging weapon as seen in whip scorpions.
“It’s like an antenna on the back end,” said Paul Selden, a paleontologist at the University of Kansas and an author of the second study.
The creature’s peculiar mix of features presented a puzzle for the teams led by Dr. Giribet and Dr. Selden. How do they classify it?
Dr. Giribet and his team suggest that C. yingi belonged to a group of extinct spider relatives called Uraraneida, which had tails. Unlike today’s spiders, uraraneids had plates on their bellies rather than squishy abdomens. They also had their silk-producing organs, or spigots, on the edges of their plates, and not on rear end spinnerets like modern spiders.
Though Dr. Selden and his colleagues agree it’s possible C. yingi may have been a part of the Uraraneida group, they also suggest that it could earn its own branch on the evolutionary tree right between spiders and Uraraneida.
Dr. Edgecombe said the two groups of researchers agreed that uraraneids were the closest relatives of spiders. But he added that the classification of whether C. yingi was more closely related to uraraneids or to modern spiders isn’t yet resolved.
Only by finding more arachnids in amber can scientists weave together the rest of the spider’s evolutionary history.