• ?Pycnogonida Latreille, 1806 (bao gồm Pantopoda Gerstaecker, 1863)

Arachnomorpha Lameere, 1890 [= Arachnata Paulus, 1979, = Palaeopoda Packard, 1903]

• Trilobita Walch, 1771
• Strabopida Hou & Bergström, 1997
• Aglaspida Walcott, 1911
• Cheloniellida Broili, 1932
• Chelicerata Heymons 1901 [= Euchelicerata Weygoldt & Paulus, 1979]
  • Class Xiphosura Latreille, 1802
  • Class Chasmataspida Caster & Brooks, 1956
  • Class Eurypterida Burmeister, 1843
  • Class Arachnida Lamarck, 1801