Eurypterid Temporal range: Ordovician–Permian | |
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Eurypterid from Ernst Haeckel's Kunstformen der Natur (1904) | |
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Order: | † Eurypterida |
The eurypterids, related to arachnids, were the largest known arthropods. They are members of the extinct order Eurypterida. It is a most diverse Chelicerate order.
The largest, such as Jaekelopterus, reached 2½ metres in length, but most species were less than 20 cm (8 inches). They were the largest arthropods of all time. They were predators which thrived in the warm, shallow seas and lakes of the Ordovician to the Permian periods, around 460 to 248 million years ago. Recent research suggsts their eyesight was not very good.
The move from the sea to fresh water probably occurred by the Pennsylvanian period. Eurypterids went extinct during the Permian–Triassic extinction event 251 million years ago, and their fossils have a near global distribution.