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Arachnomorpha is a subdivision or clade of Arthropoda, comprising the monophyletic group formed by the trilobites, other great appendage arthropods and trilobite-like families (Helmetiidae, Xandarellidae, Naraoiidae, Liwiidae, and Tegopeltidae), and a diverse sister clade including the chelicerates. Great debate is held on the position of the Pycnogonida, which are currently thought not to be placed in the immediate vicinity of the Chelicerata. Arachnomorpha are considered the sister group to the crustaceans, which are increasingly being accepted as members of the mandibulate clade (including insects and myriapods).〔 The arachnomorph concept has been challenged by suggestions that the trilobites fall in the mandibulata stem-group. There is no consensus as to assigning Arachnomorpha a formal Linnean rank. A proposal, which contraposed many synapomorphies uniting them to the Trilobita instead. to consider the Olenellinae as sister group to the Chelicerata has been refuted. ==Classification== *?Pycnogonida Latreille, 1806 (incl. Pantopoda Gerstaecker, 1863) Arachnomorpha Lameere, 1890 (Arachnata Paulus, 1979, = Palaeopoda Packard, 1903 ) *Trilobita Walch, 1771 *Megacheira Hou & Bergstrom, 1997 *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 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Arachnomorpha」の詳細全文を読む スポンサード リンク
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