Fossil shows how claws originated 390 mn years ago

February 7th, 2009 - 3:34 pm ICT by IANS  

Washington, Feb 7 (IANS) The discovery of a 390 million-year-old fossil has provided a missing link in the evolution of the front claw of scorpions and horseshoe crabs.The specimen, named Schinderhannes bartelsi, was found fossilised in slate from a quarry near Bundenbach in Germany, a site that yields spectacularly durable pyrite-preserved fossils - findings collectively known as the Hunsrück Slate.

The Hunsrück Slate has previously produced some of the most valuable clues in understanding the evolution of arthropods - including early shrimp-like forms, a scorpion and sea spiders as well as the ancient arthropods trilobites.

“With a head like the giant Cambrian aquatic predator Anomalocaris and a body like a modern arthropod, the specimen is the only known example of this unusual creature,” said Derek Briggs, director of Yale’s Peabody Museum of Natural History and an author of the paper.

Scientists have puzzled over the origins of the paired grasping appendages found on the heads of scorpions and horseshoe crabs. The researchers suggest that Schinderhannes gives a hint, said a Peabody release.

Their appendages may be an equivalent to those found in the ancient predatory ancestor, Anomalocaris - even though creatures with those head structures were thought to have become extinct by the middle of the Cambrian Period, 100 million years before Schinderhannes lived.

These findings appeared in Science.

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