Eurypterus is an extinct arthropod, known as the Giant Sea Scorpion. They existed during the Silurian Period, from 432 to 418 million years ago.
The first fossil of Eurypterus was found in 1818 in New York by S. L. Mitchill, a fossil collector. Mitchill interpreted the appendages on the carapace as barbels arising from the mouth.
It was only after seven years, in 1825, that the American zoologist James Ellsworth De Kay identified the fossil correctly as an arthropod. He named it Eurypterus remipes and established the genus Eurypterus in the process. The name means "wide wing" or "broad paddle", referring to the swimming legs