It is with mérostomes ( Merostomata ) that belongs the Limule and all the order of the Xiphosura (Xiphosura). What differentiates the class from Mérostomes of the class of Arachnida is the function of the prosome (left former the body) and of the opisthosome (left posterior the body). The prosome plays the part of a large undivided shield, and the opisthosome consists of biramés appendices

If one adds to it Euryptérides (Eurypterida) and Chasmataspides (Chasmataspida), fossils, this class is probably Paraphylétique.

The mérostomes , the Pycnogonides and the Arachnides are, among the Arthropodes, of the Chélicérates.

List orders

• order Eurypterida †
• order Chasmataspida †
• order Xiphosura
• sub-order Limulina
• family Limulidae
• kind Carcinoscorpius
• Carcinoscorpius rotundicauda
• kind Limulus
• Limulus polyphemus
• kind Tachypleus
• Tachypleus tridentatus
• Tachypleus gigas

External bonds

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