1. Extinct marine arthropods of the Paleozoic era, resembling large scorpions with flattened bodies and swimming appendages.
Usage: paleontology; plural form; singular is eurypterid; also called sea scorpions

Examples

• Eurypterids were among the largest arthropods ever to exist, some reaching lengths of over nine feet.
• Scientists study eurypterids to understand the evolution of early marine life.
• The fossil record shows that eurypterids dominated ocean ecosystems during the Silurian period.
• Unlike modern scorpions, eurypterids were fully aquatic creatures.
• Eurypterids went extinct at the end of the Permian period, about 252 million years ago.