舌形动物類（學名：），又称五口动物類，是动物界的一个分類。属于無脊椎動物，介乎於环节动物和节肢动物之间，均為寄生性動物。其特徵是体软、扁而长，无色，透明，无足。身長從數毫米到十數厘米，体表分近百个清晰的节段，内部却并不分节。舌形動物均為雌雄异体的專性寄生物：牠們的身體没有呼吸系统、和循环系统，虫体前端口部突出，呈椭圆形，周围有兩對可伸缩的钩，用以附着在寄主组织上。
本物種的名稱是因為從其部分物種的外型酷似脊椎動物的舌頭，因而為名；而其學名及另一名稱「五口動物」的來源，則是因為其口器的五個鈎，好像有五個口一樣，因而為名。這五個「鈎」，其實只有一個是真的口器、其餘四個只是顎足。過往由於對本分類物種的分類不明，單單從外形來判斷，所以將其歸類到門一層。後來到了2001年，研究證據顯示五口動物實為退化了的寄生性節肢動物，本物種生物跟其他物種的關係得到確認，所以被降至歸入成為顎足綱的一員，是為舌形亞綱。隨著顎足動物的分類被重組，舌形亞綱亦被重新分類，成為了寡甲總綱魚介形綱的成員。

現時本分類有物種約130個，皆為被動式寄生物，其部分解剖結果為退化性。成年的舌蟲長約 ，多數於宿主的呼吸系統黏付着。

分類
以下為这是马丁和戴维斯在2001年成立的分类，将五口动物置于甲壳亚门顎足綱。以下包含现存的目、超科、科、属和种：

頭行目 Cephalobaenida Heymons, 1935
Cephalobaenidae Heymons, 1922
Cephalobaena Heymons, 1922
Cephalobaena tetrapoda Heymons, 1922
孔头舌虫目 Porocephalida
Linguatuloidea 
Linguatulidae Haldeman, 1851
Linguatula Frölich, 1789
Linguatula arctica Riley, Haugerud & Nilssen, 1987
Linguatula multiannulata Haffner & Rack in Haffner, Rack & Sachs, 1969
Linguatula recurvata (Diesing, 1850)
Linguatula serrata Frölich, 1789
Neolinguatula Haffner & Rack in Haffner, Rack & Sachs, 1969
Neolinguatula nuttalli (Sambon, 1922)
Subtriquetridae Fain, 1961
Subtriquetra Sambon, 1922
Subtriquetra megacephalum (Baird, 1853)
Subtriquetra rileyi Junker, Boomker & Booyse, 1998
Subtriquetra shipleyi Hett, 1924
Subtriquetra subtriquetra (Diesing, 1836)
孔頭舌蟲總科 Porocephaloidea 
孔头舌虫科 Porocephalidae Sambon, 1922
舌蟲屬 Armillifer Sambon, 1922
Armillifer aborealis Riley & Self, 1981
Armillifer agkistrodontis Self & Kuntz, 1966
Armillifer armillatus (Wyman, 1845)
Armillifer australis Heymons, 1935
Armillifer grandis (Hett, 1915)
Armillifer mazzai (Sambon, 1922)
Armillifer moniliformis (Diesing, 1836)
Armillifer yoshidai Kishida, 1928
Cubirea Kishida, 1928
Cubirea annulata (Baird, 1853)
Cubirea pomeroyi (Woodland, 1921)
Elenia Heymons, 1932
Elenia australis Heymons, 1932
Gigliolella Chabaud & Choquet, 1954
Gigliolella brumpti (Giglioli, 1922)
Kiricephalus Sambon, 1922
Kiricephalus clelii Riley & Self, 1980
Kiricephalus coarctatus (Diesing, 1850)
Kiricephalus constrictor Riley & Self, 1980
Kiricephalus gabonensis Riley & Self, 1980
Kiricephalus pattoni (Stephens, 1908)
Kiricephalus tortus (Shipley, 1898)
Parasambonia Stunkard & Gandal, 1968
Parasambonia bridgesi Stunkard & Gandal, 1968
Parasambonia minor Riley & Self, 1982
Porocephalus Humboldt, 1812
Porocephalus basiliscus Riley & Self, 1979
Porocephalus benoiti Fain, 1960
Porocephalus bifurcatus
Porocephalus clavatus (Wyman, 1845)
Porocephalus crotali Humboldt, 1812
Porocephalus dominicana Riley & Walters, 1980
Porocephalus stilesi Sambon in Vaney & Sambon, 1910
Porocephalus subuliferum (Leuckart, 1860)
Porocephalus taiwana Qiu, Ma, Fan & Lu, 2005
Porocephalus tortugensis Riley & Self, 1979
Waddycephalus Sambon, 1922
Waddycephalus calligaster Riley & Self, 1981
Waddycephalus komodoensis Riley & Self, 1981
Waddycephalus longicauda Riley & Self, 1981
Waddycephalus porphyriacus Riley & Self, 1981
Waddycephalus punctulatus Riley & Self, 1981
Waddycephalus radiata Riley & Self, 1981
Waddycephalus scutata Riley & Self, 1981
Waddycephalus superbus Riley & Self, 1981
Waddycephalus teretiusculus (Baird, 1862)
Waddycephalus vitiensis Heymons, 1932
Sebekidae Sambon, 1922
Alofia Giglioli in Sambon, 1922
Alofia ginae Giglioli in Sambon, 1922
Alofia indica (von Linstow, 1906)
Alofia merki <small>Giglioli 'in Sambon, 1922</small>Alofia nilotici Riley & Huchzermeyer, 1995Alofia parva Riley & Huchzermeyer, 1995Alofia platycephalum (Lohrmann, 1889)Alofia simpsoni Riley, 1994Alofia travassosi (Heymons, 1932)Diesingia Sambon, 1922Diesingia kachugensis (Shipley, 1910)Diesingia megastomum (Diesing, 1836)Selfia Riley, 1994Selfia porosus Riley, 1994Leiperia Sambon, 1922Leiperia australiensis Riley & Huchzermeyer, 1996Leiperia cincinnalis (Sambon in Vaney & Sambon, 1910)Leiperia gracilis (Diesing, 1836)Sambonia Noc & Giglioli, 1922Sambonia clavata (Lohrmann, 1889)Sambonia parapodum Self & Kuntz, 1966Sambonia solomenensis (Self & Kuntz, 1957)Sambonia varani (Self & Kuntz, 1957)Sambonia wardi (Sambon in Vaney & Sambon, 1910)Agema Riley et al., 1997Agema silvaepalustris Riley et al., 1997Pelonia Junker & Boomker, 2002Pelonia africana Junker & Boomker, 2002Sebekia Sambon, 1922Sebekia cesarisi Giglioli in Sambon, 1922Sebekia divestei Giglioli in Sambon, 1922Sebekia johnstoni Riley, Spratt & Winch, 1990Sebekia microhamus Self & Rego, 1985Sebekia minor (Wedl, 1861)Sebekia mississippiensis Overstreet, Self & Vliet, 1985Sebekia multiannulata Riley, Spratt & Winch, 1990Sebekia novaeguineae Riley, Spratt & Winch, 1990Sebekia okavangoensis Riley & Huchzermeyer, 1995Sebekia oxycephalum (Diesing, 1836)Sebekia purdieae Riley, Spratt & Winch, 1990Sebekia trinitatis Riley, Spratt & Winch, 1990
Raillietiellida Almeida & Christoffersen, 1999
Raillietiellidae Sambon, 1922Raillietiella Sambon, 1910Raillietiella aegypti Ali, Riley & Self, 1982Raillietiella affinis Bovien, 1927Raillietiella agcoi Tubangui & Masiluñgan, 1936Raillietiella ampanihyensis Gretillat, Brygoo & Domergue, 1962Raillietiella amphiboluri Mahon, 1954Raillietiella belohaensis McAllister, Riley, Freed & Freed, 1993Raillietiella bicaudata Heymons & Vitzthum, 1935Raillietiella boulengeri (Vaney & Sambon, 1910)Raillietiella bufonis Ali, Riley & Self, 1982Raillietiella cartagenensis Ali, Riley & Self, 1985Raillietiella chamaeleonis Gretillat & Brygoo, 1959Raillietiella colubrilineati (Leuckart, 1860)Raillietiella congolensis Fain, 1961Raillietiella crotali Ali, Riley & Self, 1984Raillietiella freitasi (Motta & Gomes, 1968)Raillietiella furcocercum (Diesing, 1836)Raillietiella gehyrae Bovien, 1927Raillietiella gigliolii Hett, 1924Raillietiella gowrii Rajalu & Rajendran, 1970Raillietiella hebitihamata Self & Kuntz, 1960Raillietiella hemidactyli Hett, 1934Raillietiella indica Gedoelst, 1921Raillietiella kochi Heymons, 1926Raillietiella mabuiae Heymons, 1922Raillietiella maculatus Rao & Hiregaudar, 1962Raillietiella maculilabris Ali, Riley & Self, 1984Raillietiella madagascariensis McAllister et al., 1993Raillietiella mediterranea (Hett, 1915)Raillietiella monarchus Ali, Riley & Self, 1984Raillietiella morenoi Abreu-Acosta et al., 2006Raillietiella mottae Almeida, Freire & Lopes, 2008Raillietiella namibiensis Riley & Heideman 1998Raillietiella orientalis (Hett, 1915)Raillietiella piscator Nair, 1967Raillietiella rileyi Krishnasamy et al., 1995Raillietiella schoutedeni Fain, 1960Raillietiella scincoides Ali, Riley & Self, 1984Raillietiella spiralis Hett, 1924Raillietiella teagueselfi Riley, McAllister & Freed, 1988Raillietiella tetrapoda (Gretillat, Brygoo & Domergue, 1962)Raillietiella trachea Riley, Oaks & Gilbert, 2003Raillietiella venteli (Motta, 1965)Yelirella Spratt, 2010Yelirella petauri (Spratt, 2010)
Reighardiida Almeida & Christoffersen, 1999
Reighardiidae Heymons, 1926Hispania Martínez et al., 2004Hispania vulturis Martínez et al., 2004Reighardia Ward, 1899Reighardia lomviae Dyck, 1975Reighardia sternae'' (Diesing, 1864)

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 舌形虫病或人舌形虫病

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