Learn how to say Eurypterids correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word eurypterid:
a giant fossil marine arthropod of a group occurring in the Palaeozoic era. They are related to horseshoe crabs, and resemble large scorpions with a terminal pair of paddle-shaped swimming appendages.
Subclass Eurypterida, class Merostomata, subphylum Chelicerata
late 19th century: from modern Latin Eurypterus (genus name), from eury- + Greek pteron ‘wing’ + -id2