肢口纲

**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）