A tail of the type now seen on scorpions has been found on some spiders preserved in amber for around 100 million years.
© Lucas T. Jahn, Shuttertock
Writing in ‘Nature’ the research team reports two specimens are available, helping to further our understanding of how spiders evolved. ‘It is a key fossil for understanding spider origins,’ said paleontologist Bo Wang of the Chinese Academy of Sciences, quoted by ‘Reuters’. ‘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.’
So what was the tail for?
Speculating on the nature of the tail, University of Kansas paleontologist Paul Selden said, ‘Any sort of flagelliform appendage tends to be like an antenna. It’s for sensing the environment. Animals that have a long whippy tail tend to have it for sensory purposes.’ Perhaps the tail was for sensing both prey, predators and the world around them.
Having been found in amber, there are speculations that the spiders might have lived in the leaf mold and moss at the foot of trees. Selden explains, ‘All specimens are adult males, which would have been roving around looking for females at this point in their lives. ‘
If a tailed spider which shares a characteristic with scorpions is making you uneasy, aside from the fact that it would have done it’s scuttling around while dodging dinosaurs you can also take comfort from the fact that it was tiny. Chimerarachne, which is also fanged, was only about 7.5 millimeters long, and more than half of that was tail.
A long history shrouded in mystery
The latest in a series of Cretaceous-period fossils from the amber deposits in northern Myanmar’s Hukawng Valley, these fossils are helping to plug a gap in our knowledge of how spiders evolved. The researchers explain that the details of spiders’ origins remain obscure, with little knowledge of their stem group and few insights into the sequence of character acquisition during spider evolution.
Arachnids have been around considerably longer than arachnophobes. 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. ‘Chimerarachne could be considered as a spider. It all depends on where we decide to draw the line,’ Selden said.
He added that Chimerarachne most likely wove a sheet web, and possibly a burrow lined with silk; they were unlikely to be web spinners. Spiders use silk for a great many purposes, of which prey-capture webs is just one. Egg-wrapping is a vital function for spider silk, as well as laying a trail to find its way back home.