Editing Atlantic horseshoe crab (section)

==Names and classification==
[[File:Horseshoe crab with shells.JPG|thumb|upright=1.0|Atlantic horseshoe crab with attached ''[[Crepidula]]'' shells on the Delaware Bay beach in Villas, [[New Jersey]].]]
[[File:Atlantic horseshoe crab (Limulus polyphemus) (5).jpg|alt=Underside of living horseshoe crab|thumb|Underside view of a living male crab, showing the mouth, gills and legs]]
This group of animals is also known as '''horsefoot''', or '''saucepan'''. Some people call the horseshoe crab a "helmet crab", but this common name is more frequently applied to a true crab, a [[malacostracan]], of the species ''[[Telmessus cheiragonus]]''. The term "king crab" is sometimes used for horseshoe crabs, but it is more usually applied to a group of [[decapoda|decapod]] crustaceans.

''Limulus'' means "askew"<ref name="Coast by Willie Heard">{{Cite journal |url=http://www.marine.usf.edu/pjocean/packets/f01/f01u5p3.pdf |last=Heard |first=Willie |title=Coast |date=Fall 2001 |journal=Project Oceanography |pages=81–91 |access-date=5 July 2008 |archive-url=https://web.archive.org/web/20170219095700/http://www.marine.usf.edu/pjocean/packets/f01/f01u5p3.pdf |archive-date=19 February 2017 |url-status=dead }}</ref> and ''polyphemus'' refers to [[Polyphemus]], a giant in Greek mythology.<ref name="Coast by Willie Heard"/> It is based on the misconception that the animal had a single eye.

Former scientific names include ''Limulus cyclops'', ''Xiphosura americana'', and ''Polyphemus occidentalis''.

It is the tail that earns this order its name Xiphosura, which derives from the ancient Greek word for "sword tail".

Studies of [[microsatellite DNA]] have revealed several distinct geographic groups in the Atlantic horseshoe crab. While there is extensive mixing between neighbouring populations, primarily due to movements by males, there is little or no mixing between the US and isolated [[Yucatán Peninsula]] horseshoe crabs, leading some to suggest that a [[Taxonomy (biology)|taxonomic]] review is necessary.<ref name=Zaldivar2009/><ref name=King2005>{{cite journal| author1=King, T.L. | author2=Eackles, M.S. | author3=Spidle, A.P. | author4=Brockmann, H.J. |author-link4=H. Jane Brockmann | year=2005 | title=Regional differentiation and sex-biased dispersal among populations of the horseshoe crab ''Limulus polyphemus'' | journal=Transactions of the American Fisheries Society | volume=134 | issue=2 | pages=441–465 | doi=10.1577/T04-023.1 | bibcode=2005TrAFS.134..441K }}</ref>