Prof Michael Akam, Head of the Department of Zoology at the University of Cambridge, and former Director of the Museum of Zoology, writes:
The Eurypterids, or Sea Scorpions, were the most terrifying group of arthropods that ever lived, roaming the Paleozoic seas from about 460-255 million years ago. The fossil specimens that we have in the Museum are quite small, 15-20cm, but the largest specimens were truly fearsome predators – up to 2.5m long, with single claws of more than 80cm. Our specimens come from New York State, an area famed for them. Indeed, sea scorpions are the State Fossil of New York.
I visited one of the fossil quarries myself. We contacted the owner, who invited us to visit his workshop. It looks like any other small farmstead in upstate New York, nestled in the hills. His barn, though, is full not of hay and horses, but rock saws and air drills, for preparing these most wonderful fossils, which he displays all over his house (and on the internet too, at http://langsfossils.com/eurypterids.htm)
I’m no palaeontologist, but even so, he took us up to the quarry behind the house, handed us a hammer and chisel, and invited us to split some of the blocks of shale he had excavated the previous year, and left for the frost to weaken. The eurypterids are so abundant in this rock, that almost every split yielded a fossil or two.
Eurypterids belong to the large group of arthropods called chelicerates – a group characterised by having pincers rather than antennae as their front limbs. Spiders and scorpions are the most familiar living chelicerates, but these land animals are only distantly related to the sea scorpions. The closest living relatives of the sea scorpions are probably the horseshoe crabs – another ancient group of wonderful arthropods, and the only marine chelicerates to survive to the present day.