Ancient Arachnid Preserved in Amber

A rare relative of spiders has been discovered preserved in 40 million year old amber.  The little creature was trapped in pine resin and preserved with the resin eventually turning into amber.  This rare specimen identified as a Harvestman (Dicranopalpus ramiger), has been donated to the London Natural History Museum.

The amber, which was from the Baltic area dates from the late Eocene, amber of this age and from the Baltic is fairly common but to find such a rare and complete specimen so well preserved is a very special event.  It seems that around 40 million years ago, a tiny harvestman climbed up a pine trunk, encountered a lump of thick, sticky tree sap and was engulfed.  The whole animal was trapped, a set of events leading to the preservation of this relative of true spiders for scientists to study.

A Rochester-based fossil collector (Rochester in Kent, England); had purchased a number of amber pieces on an on-line auction website, on receiving the goods, a close examination of the amber revealed a tiny leg hiding in one piece.  He carefully polished it and slowly removed some layers to reveal the complete fossil of this tiny forest inhabitant of the Cenozoic.  Realising he had found something unusual the specimen was sent to the London Natural History museum for expert analysis.

A Close up of the Tiny Fossil Harvestman

Picture Credit: Kent News

The fossil can be seen in the amber slice, to the left of centre.

Dr Andrew Ross, Collection Manager of fossil invertebrates and plants at the museum commented:

“when we looked at the amber under the microscope we could see it was a harvestman”.

Harvestmen belong to the Arachnid class, the earliest fossil Harvestmen date from the Lower Carboniferous deposits from East Kirkton, Scotland.  A fossil Harvestman from these deposits, an Opilonid has been dated to around 320 million years ago, although these creatures may have existed even earlier, perhaps being some of the first creatures to adapt fully to a terrestrial lifestyle.

Today there are around 26 species of Harvestmen in the UK. They may look like spiders with their eight legs but this is only a superficial similarity.  Harvestman have no silk glands, they cannot spin silk, they have not got the ability to defend themselves with a poisonous bite, their only means of defence in most species is to produce a foul smelling chemical to put off a would be attacker.

Spiders have a segmented body, with a head, thorax and abdomen clearly divided.  Harvestmen have a fused body with no body segments

“This one is quite a young animal”, 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 creatures try to escape the sticky resin”.

Amber is an important preservation medium, allowing the preservation of small, delicate bodied animals that would not normally be preserved in rock.  This find of a species now extinct helps scientist’s to build up a picture of the ecosystem in those ancient Baltic forests.

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