Eurypterids, or sea scorpions, are a type of ancient chelicerates the lived from the Darriwilian of the Ordovician (470 mya) to the end of the Permian, 250 mya. Despite the common name being sea scorpions, they are actually more closely related to horseshoe crabs. They appeared in Death Rays.

In Animal ArmageddonEdit

In Death RaysEdit

Eurypterids are depicted as prey for straight-shelled nautiloids. During the mass extinction, due to the straight-shelled naultiloids shrinking in size, they rise up the food chain to become top predators, evolving into the largest arthropod of all time, Pterygotus. It was also shown that the Eurypterid could also crawl onto land, at least for a short amount of time, giving them another advantage to the straight-shelled nautiloids.


  • During the Ordovician, the kind of eurypterid shown is Megalograptus.
  • The official website misidentified Pterygotus as Jaekelopterus, a related, yet slightly bigger, eurypterid.