Published: Wed, February 07, 2018
Science | By Eileen Rhodes

Fossils In Amber May Provide Link Between Ancient Arachnids And Modern Spiders

Fossils In Amber May Provide Link Between Ancient Arachnids And Modern Spiders

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

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.

The recent discovery of four of these creatures in northern Myanmar, trapped in amber for 100 million years, has blown the door wide open for researchers to establish a link between ancient and modern day arachnids, the BBC News reported. Given it was encased in amber, Chimerarachne must have lived on or around tree trunks, and like its modern counterparts it most likely would have fed on insects. What's awesome is that the amber process preserves parts that wouldn't be conserved through regular fossilization. Numerous other often-spectacular Cretaceous amber finds coming out of Southeast Asia these days (see, for example, the tick preserved clinging to a dinosaur feather or 2016's entire feathered dinosaur tail) have taken a similar route to scientific notice.

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. This latest collection of finds ended up with two different research groups at the Nanjing Institute of Geology and Palaeontology.

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The odd creature shares certain characteristics with modern spiders - including fangs, four walking legs and silk-producing organs at its rear - however, it also has a long tail, or flagellum - a feature that living spiders lack.

"We don't know if it wove webs". Fleur reports for the New York Times, the newly discovered arachnid has at least one feature that sets it apart from any living spider: a tail.

Called a telson, it can be seen today in scorpions - but it has never been known before in a spider. Researchers think C. yingi used its appendage to sense its environment. (Unlike modern day spiders, uraraneids had plated bellies and silk-spinning organs on the edges of their plates, rather than near their rear end). A rather unexpected way scientists could confirm this hunch is by discovering some of C. yingi's tailed descendents in the jungle. But, despite some differences, "they draw the same conclusion-that fossil uraraneids, as this group is called, are the closest extinct relatives of spiders", says Greg Edgecombe, a paleobiologist at the Natural History Museum in London, who was not involved with the work. "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". Some argue that spinnerets were the key innovation that allowed spiders to become so successful; there are almost 50,000 known spider species alive today. "We haven't found them, but some of these forests aren't that well-studied, and it's only a tiny creature".

The finding has been described in a paper appearing in Nature Ecology and Evolution by an global team, including Paul Selden of the Paleontological Institute and Department of Geology at the University of Kansas.

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