n.large extinct scorpion-like arthropod considered related to horseshoe crabs
英汉双解大词典
eurypterid/jʊˈrɪptərɪd/
1.
N（名词）
any large extinct scorpion-like aquatic arthropod of the group Eurypterida, of Palaeozoic times, thought to be related to the horseshoe crabs 板足鲎目动物