100-Million-Year-Old "Chimera" Arachnids In Amber Shine A Light On The Construction Of Spiders

Robin Andrews 05 Feb 2018, 16:00

Defining a new species using fossilized or preserved remnants of a long-dead critter is far from easy. Apart from the fact that the concept of a species itself is somewhat nebulous, palaentologists have to generally rely on common and unique physical features to compare and contrast with other animals.

In this case, this chimeric spider’s features have caused a little trouble. There’s no doubt that it’s a new species, one that roamed what is now Myanmar at the same time as tank-sized dinosaurs wandered across what is now Maryland, but the teams can’t quite agree as to where it should fit on the evolutionary tree.

Talking to IFLScience about the “stunning” fossils, Dr Russell Garwood, a lecturer at the School of Earth and Environmental Sciences at the University of Manchester – and co-author of the Araneae-leaning paper – explains that the findings in the two papers are nevertheless pretty similar.

“Any apparent differences largely boil down to the semantics about how you define a spider. Should it be a thing that has spinnerets, or a thing that has lost a tail, say?”

“I don't think this is as interesting a question as the other implications of both studies – that building a spider, as it were, is a series of step-wise changes, and we're gradually working out which order these came in!”

The Araneae order goes back at least 305 million years, long before dinosaurs walked the Earth. The Uraraneids emerge a little later during the Permian Period, shortly before the greatest mass extinction in Earth’s history took place – something both lineages clearly withstood.

This discovery “means that there was a lineage of tailed spider-like things that survived for at least another 200 million years for us to find this specimen,” something that Garwood considers to be “really kinda cool, and totally unexpected.”

Whatever the order, that fact alone makes this chimera a stunning piece of biological machinery with a storied legacy.

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