Eurypterus is an extinct genus of eurypterid, a group of organisms commonly called "sea scorpions". The genus lived during the Silurian period, from around 432 to 418 million years ago. Eurypterus is by far the most well-studied and well-known eurypterid. Eurypterus fossil specimens probably represent more than 95% of all known eurypterid specimens.
Eurypterus
Painting painted in 1912 by Charles R. Knight depicting various eurypterids discovered in New York. The painting includes Dolichopterus, Eusarcana, Stylonurus, Eurypterus and Hughmilleria.
E. remipes from the State Museum of Natural History Karlsruhe, Germany.
E. lacustris from the Muséum national d'histoire naturelle, France.
Eurypterids, often informally called sea scorpions, are a group of extinct arthropods that form the order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period 467.3 million years ago. The group is likely to have appeared first either during the Early Ordovician or Late Cambrian period. With approximately 250 species, the Eurypterida is the most diverse Paleozoic chelicerate order. Following their appearance during the Ordovician, eurypterids became major components of marine faunas during the Silurian, from which the majority of eurypterid species have been described. The Silurian genus Eurypterus accounts for more than 90% of all known eurypterid specimens. Though the group continued to diversify during the subsequent Devonian period, the eurypterids were heavily affected by the Late Devonian extinction event. They declined in numbers and diversity until becoming extinct during the Permian–Triassic extinction event 251.9 million years ago.
Eurypterid
Illustration of Hibbertopterus, a large stylonurine (lacking swimming paddles) eurypterid
The holotype of Palmichnium kosinkiorum, containing the largest eurypterid footprints known
The supposed "gill tracts" of eurypterids have been compared to the air-breathing pseudotracheae present in the posterior legs of modern isopods, such as Oniscus (pictured).