xiph·o·su·ran 
(zĭf′ə-srən)
(zĭf′ə-srən)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 the Appendix of Indo-European roots.]
xiph′o·suran adj.