肢口綱（學名：Merostomata）是一綱水生的螯肢亞門，其下包括了鱟。現存的肢口綱只剩一個劍尾目 4 個物種，分別為中華鱟、南方鱟、美洲鱟、圓尾鱟，但有大量主要屬於古生代的化石物種。

肢口綱是螯肢亞門之中唯一擁有複眼的，而蛛形綱則失去了節肢動物祖先發展完好的側前複眼。

史前的板足鱟綱（Eurypterida）曾被歸類為本綱之下的一個亞綱，但後來被許多學者認為更接近蛛形綱，因而將板足鱟綱分出去獨立成為一綱，與蛛形綱另組成硬器類（Sclerophorata）或 Cryptopneustida。



詞源

肢口綱的學名「Merostomata」是從希臘文 μηρός（meros，「大腿」）和 στόμα（stoma，「口」）組合而來，因本綱動物的口器附近擁有附肢而得名。



下屬分類

本綱包括以下目：


* 劍尾目 _Xiphosurida_

目的地位未定的科：


* _Adelophthalmidae_

* _Brachyopterellidae_

* _Bunodidae_

* _Carcinosomatidae_

* _Chasmataspidae_

* _Cyrtoctenidae_

* _Diploaspididae_

* _Dolichopteridae_

* _Drepanopteridae_

* _Erieopteridae_

* _Euproopidae_

* _Eurypteridae_

* _Hardieopteridae_

* _Heteroaspididae_

* _Heterolimulidae_

* _Hibbertopteridae_

* _Hughmilleriidae_

* _Jaekelopteridae_

* _Kokomopteridae_

* _Lanarkopteridae_

* _Laurieopteridae_

* _Liomesaspidae_

* _Liomesaspididae_

* _Megalograptidae_

* _Mixopteridae_

* _Moravuridae_

* _Moselopteridae_

* _Mycteropidae_

* _Parastylonuridae_

* _Pterygotidae_

* _Rhenopteridae_

* _Slimoniidae_

* _Stylonuridae_

* _Weinberginidae_

* _Woodwardopteridae_

目和科的地位未定的屬：


* _Aglaspidichnus_ Radwanksi & Roniewicz, 1967

* _Anderella_ Moore, McKenzie & Lieberman, 2007

* _Anthraconectes_ Meek & Worthen, 1868

* _Baltoeurypterus_ Størmer, 1973

* _Beaumontia_ David, 1928

* _Belinuropsis_ Matthew, 1909

* _Bembicosoma_ Laurie, 1900

* _Bembycosoma_ Laurie, 1900

* _Bifarius_ Tasch, 1961

* _Borchgrevinkium_ Novojilov, 1958

* _Brachopterella_

* _Bunaia_ Clarke, 1920

* _Camanchia_ Moore, Briggs, Braddy & Shultz, 2011

* _Caragassia_ Vologdin, 1965

* _Carbonolimulus_ Hong, 1985

* _Chasmataspis_ Caster & Brooks, 1956

* _Curviramus_ Ruedemann, 1935

* _Cyamocephalus_ Currie, 1927

* _Dibasterium_ Briggs, Siveter, Siveter, Sutton, Garwood & Legg, 2012

* _Dickinsonia_ Tasch, 1963

* _Dipeltis_ Packard, 1885

* _Dvulikiaspis_ Marshall, Lamsdell, Shpinev & Braddy, 2013

* _Elleria_ Raymond, 1944

* _Elmocephalus_ Tasch, 1964

* _Eocarcinsoma_ Caster & Kjellesvig-Waering, 1964

* _Eurypterella_ Matthew, 1889

* _Eusarcus_ Grote & Pitt, 1875

* _Exoculatus_ Pirozhnikov, 1966

* _Gdowia_ Yanishevsky, 1950

* _Glaucodes_ Pruvost, 1924

* _Grossopterus_ Størmer, 1935

* _Habcyne_ Meyer, 1844

* _Hastimima_ Seward, 1909

* _Heteroaspis_ Stormer, 1972

* _Holmipterus_ Kjellesvig-Waering, 1979

* _Hypatocephala_ Tasch, 1961

* _Ikeyia_ Vologdin, 1965

* _Iyaia_ Vologdin, 1965

* _Kasibelinurus_ Pickett, 1993

* _Kioeria_ Størmer, 1933

* _Lagrandella_ Eldredge, 1974

* _Laurieopterus_

* _Legrandella_ Eldredge, 1974

* _Limulicubichnus_ Miller, 1982

* _Limulites_ Krueger, 1823

* _Mazonipterus_ Kjellesvig-Waering, 1963

* _Nahlyostaspis_ Marshall, Lamsdell, Shpinev & Braddy, 2013

* _Neobelinuropsis_ Eller, 1938

* _Neolimulus_ Woodward, 1868

* _Onychopterella_ Størmer, 1951

* _Orcanopterus_ Stott, Tetlie, Braddy, Nowlan, Glasser & Devereux, 2005

* _Palatinaspis_ Malz & Poschmann, 1993

* _Paraeurypterus_ Lamsdell, Hosgör & Selden, 2013

* _Parahughmillera_ Kjellesvig-Waering, 1961

* _Parka_ Fleming, 1864

* _Pasternakevia_ Selden & Drygant, 1987

* _Pentlandopterus_ Lamsdell, Hosgör & Selden, 2013

* _Permolimulinella_ Tasch, 1963

* _Pincombella_ Chapman, 1932

* _Polystomurum_ Novozhilov, 1958

* _Psammonlimulus_

* _Pseudoniscus_ Nieszkowski, 1859

* _Pseudostylonurus_ Xie & Xie, 1989

* _Raaschichnus_ Hesselbo, 1988

* _Rutroclypeus_ Withers, 1933

* _Sanctacarus_

* _Selenichnites_ Romano & Whyte, 1990

* _Skrytyaspis_ Marshall, Lamsdell, Shpinev & Braddy, 2013

* _Steropis_ Bailey, 1858

* _Strongylocephalus_ Tasch, 1961

* _Stylonarus_ Page, 1856

* _Stylonuroides_ Kjellesvig-Waering, 1966

* _Syntomopterella_ Tetlie, 2007

* _Syntomopterus_ Kjellesvig-Waering, 1961

* _Thurandina_ Stormer, 1974

* _Tremaglaspis_ Fortey & Rushton, 2003

* _Truncatiramus_ Kjellesvig-Waering, 1961

* _Willwerathia_ Stormer, 1969



註記



參考資料

石川良輔編『節足動物の多様性と系統』,(2008), バイオディバーシティ・シリーズ 6 (裳華房)



外部連結


* Horseshoe Crabs (Class Merostomata) （頁面存檔備份，存於網際網路檔案館）