Research

Spider Fossils With Tails: 'Fantastic' Arachnid Surprise

Spider Fossils With Tails: 'Fantastic' Arachnid Surprise

Two arachnids 100 million years old have been found exquisitely preserved in amber in Myanmar, shedding light on the evolution of spiders.

"We've not found fossils before that showed this, and so finding this now was a huge (but really fantastic) surprise".

Amber from Myanmar has been mined for thousands of years and traded with China as jewellery.

They look similar to modern-day spiders, and have fangs, four walking legs and silk-producing spinnerets.

Paul Selden, a palaeontologist who worked on the specimen at the University of Kansas told The Guardian that they were "a kind of missing link" between the two species - the uraraneids and primitive living spiders.

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. But experts disagree about how these fossils relate to modern-day spiders, because there's something odd about their crumpled corpses: all four of them have tails. All but the most primitive spiders have smooth backs, unlike the segmented abdomens of scorpions, which are believed to have diverged from an ancestral arachnid more than 430 million years ago.




And what is even more unbelievable, says Bond, is that the amber is only 100 million years old. This latest collection of finds ended up with two different research groups at the Nanjing Institute of Geology and Palaeontology. However, the researchers are taking their time in actually classifying this new creature because they want to be absolutely sure that it either belongs in an existing category or is the first example of an entirely new branch. The males also have modified pedipalps - syringe-like appendages on the fronts of their faces that modern spiders use during mating.

The finding is described in a paper appearing in Nature Ecology & Evolution by an global team including Paul Selden of the Paleontological Institute and Department of Geology at the University of Kansas and colleagues from China, Germany, Virginia and the United Kingdom.

Scientists have christened the hybrid beast Chimerarachne after the mythological Chimera -which is composed of the parts of several animals. The oldest-known true spiders lived about 315 millions year ago.

"Taken together, Chimerarachne has a unique body plan among the arachnids and raises important questions about what an early spider looked like, and how the spinnerets and pedipalp organ may have evolved". What is interesting about the preserved remains of ancient "proto-spiders" is that they had tails which were longer than their whole bodies. Scientists have traditionally used silk spinnerets to distinguish true spiders from other species. 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.

Professor Selden said: "We can only speculate that, because it was trapped in amber, we assume it was living on or around tree trunks".

The dorsal view of entire Chimerarachne yingi specimen. It makes us wonder if these may still be alive today.