Taxon Description (Wikipedia)
Merostomata is a class of marine class Merostomata, in favour of splitting the class into two classes, Xiphosura and Eurypterida. This is because Merostomata is thought to be paraphyletic, with the Eurypterida more closely related to the Arachnida, forming the group Metastomata (Weygoldt & Paulus 1979) or Cryptopneustida (Boudreaux, 1979). This change has not been incorporated into most textbooks, which typically use the traditional "Merostomata" without reference to the Eurypterida.
The Merostomata are the only chelicerates to possess arachnids have lost the ancestral arthropods' fully developed latero-anterior compound eyes.
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