New Haven, Conn. A missing link in the evolution of the front claw of living scorpions and horseshoe crabs was identified with the discovery of a 390 million-year-old fossil by researchers at Yale and the University of Bonn, Germany.
The specimen, named Schinderhannes bartelsi, was found fossilized in slate from a quarry near Bundenbach in Germany, a site that yields spectacularly durable pyrite-preserved fossils findings collectively known as the Hunsrck Slate. The Hunsrck Slate has previously produced some of the most valuable clues to 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 appearing in the journal Science.
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. 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.
The fossil's head section has large bulbous eyes, a circular mouth opening and a pair of segmented, opposable appendages with spines projecting inward along their length. The trunk section is made up of 12 segments, each with small appendages, and a long tail spine. Betwe
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