xiphosuran

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xiph·o·su·ran

X0007700 (zĭf′ə-so͝or′ən)n. Any of various arthropods of the order Xiphosura, having a long pointed telson extending from the rear of the abdomen. The order includes the horseshoe crabs and many extinct species.
[From New Latin Xiphosūra, order name : Greek xiphos, sword + Greek ourā, tail; see ors- in Indo-European roots.]
xiph′o·su′ran adj.

xiphosuran

(ˌzɪfəˈsjʊərən) n (Animals) any chelicerate arthropod of the subclass Xiphosura, including the horseshoe crabs and many extinct formsadj (Animals) of, relating to, or belonging to the subclass Xiphosura[C19: from New Latin Xiphosura, irregularly from Greek xiphos sword + oura tail]