Back وركيات الفم Arabic Merostomata Azerbaijani Мерастомавыя Byelorussian Merostomats Catalan Merostomata CEB Hrotnatci Czech Merostomata German Merostomoj Esperanto Merostomata Spanish Merostomata Basque
| Merostomata Temporal range:
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|---|---|
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| Reconstruction of Eurypterus (Eurypterida) | |
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| Five views of Limulus polyphemus (Xiphosura) | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Chelicerata |
| Clade: | Prosomapoda |
| Order: | Xiphosura Woodward, 1866 |
| Orders | |
Merostomata is a class of chelicerate arthropods that contains the extinct Eurypterida (sea scorpions) and the extant Xiphosura (horseshoe crabs). The term was originally used by James Dwight Dana to refer to Xiphosura only, but was emended by Henry Woodward to cover both groups.