Merostomata
A taxonomic class of aquatic chelicerate arthropods, including extinct sea scorpions (Eurypterida) and extant horseshoe crabs (Xiphosura). Used in biological and paleontological contexts.
Merostomata includes horseshoe crabs and sea scorpions.
Sea scorpion, an extinct group within Merostomata. 腿口類 encompasses both extinct and extant forms.
From 腿 (thigh) + 口 (mouth) + 類 (group), likely a calque of the scientific name Merostomata (from Greek mēros 'thigh' + stoma 'mouth'), referring to the leg-like appendages near the mouth.