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Sunday, April 27, 2008

Amber holds arachnid's secrets

About 40 million years ago, when the Earth looked dramatically different to how it does today, a tiny arachnid was crawling around in the Baltic.

But the little bug was soon to meet a sticky demise.

As it crept up a tree trunk, it encountered a blob of tree resin and its spindly legs rapidly became stuck-fast in the gluey trap.

Fast-forward a few thousand Millennia and the creature still sits in the same pose, preserved in a small lump of amber.

However, its location is now rather different from the prehistoric forest floor where it once roamed.

Terry Collingwood
I noticed something was in there hiding beneath a layer - it looked like a leg
Terry Collingwood

It can now found within the vaults of London's Natural History Museum - taking pride of place as the latest donation in the museum's palaeontology collection.

"You can just spend hours and hours looking at amber," said Terry Collingwood, who discovered the amber-encased creature.

The Rochester-based fossil collector had bought a batch of amber on an online auction site before noticing, on closer inspection, that one of the pieces looked a little unusual.

"I spent a long time looking at this piece and then I noticed something was in there hiding beneath a layer - it looked like a leg.

"So I started to work on the piece, polishing it and working to get those layers off.

"And then I eventually saw it - I realised straightaway that it was something special."

Stuck fast

He sent the mysterious creature off to the Natural History Museum to be checked out.

"When we looked at the amber under the microscope we could see it was a harvestman," said Dr Andrew Ross, collection manager of fossil invertebrates and plants.

Harvestmen belong to the arachnid class.

At first glance, with their eight legs, they look similar to spiders. But, while spiders' heads and abdomens are segmented, harvestmen's bodies and heads are fused together. They also lack silk glands - making spinning webs impossible.

Amber with arachnid (NHM)
Usually some of the legs will snap off as the insects try to escape the sticky resin, but this one must have got stuck fast
Dr Andrew Ross, Natural History Museum

Closer examination revealed that the specimen was rare, a species called Dicranopalpus ramiger, which is now extinct.

"This one is quite a young spider", explained Dr Ross. "Its body is the size of a pinhead and its legs are about 6mm long.

"But what is really interesting is that all of its legs are still intact - usually some of the legs will snap off as the insects try to escape the sticky resin, but this one must have got stuck fast."

Dr Ross said that fossil finds like this recent donation from Mr Collingwood were extremely important.

He said: "They are a record of something that lived millions and millions of years ago.

"Amber is particularly special. It preserves some of the smaller animals that you don't get preserved in rock.

"It gives us a fantastic insight into lots of prehistoric insects."

Mr Collingwood added: "I just love insects in amber. Knowing something is going to be at the Natural History Museum is just wonderful."

Source

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