扁蜷科（學名：），亦作扁卷螺科，是腹足綱之下的一個單系群支序，本科物種皆為可呼吸空氣的淡水螺。原屬有肺目基眼亞目椎實螺總科，今屬異鰓類泛有肺類喜溼螺類支序。 本科多個物種的外殼都是平旋殼，與一般腹足綱物種的外殼形狀不同。外殼看似是右旋，但其實是螺把殼上下顛倒來揹在身上，使左旋的外殼看起來像是右旋。 因其外形，本科物種又稱。 由於本科物種的頭和腹足都比較細小，使得牠們頭上絲般幼的觸角顯得很細長。 分類 對於部份分類元來說，是否應該歸入扁蜷科仍有爭議。這對於淡水帽貝 Ferrissia 跟 Ancylus 這兩個屬來說由其合適。這些屬有時會被歸入椎實螺科（Lymnaeidae Rafinesque 1815）；另外亦有文獻把上述兩個屬放進各自的一個科裡。然而，在布歇特和洛克羅伊的腹足類分類 2005 年 的分類，這些屬被歸為扁蜷亞科（Planorbinae）之下的 Ancylini 族。以下將詳述這個分類的具體內容。 2005 年分類 根據布歇特和洛克羅伊的腹足類分類 2005 年，本科包括下列各個亞科： 扁蜷亞科 Planorbinae Rafinesque 1815 扁蜷族 Planorbini Rafinesque 1815：synonyms Choanomphalinae P Fisher Crosse 1880 Orygoceratidae Brusina 1882 tribe Ancylini Rafinesque 1815 synonym Pseudancylinae Walker 1923 inv tribe Biomphalariini H Watson 1954 synonyms Acrorbini Starobogatov 1958 Drepanothrematini Zilch 1959 Taphiinae Harry Hubendick 1964 tribe Planorbulini Pilsbry 1934 tribe Segmentinini FC Baker 1945 subfamily Bulininae P Fischer Crosse 1880 tribe Bulinini P Fischer Crosse 1880 synonyms Laevapicinae Hannibal 1912 Isidorinae Annandale 1922 Gundlachiinae Starobogatov 1967 tribe Coretini Gray 1847 synonyms Pompholicinae Dall 1866 inv Camptoceratinae Dall 1870 Megasystrophinae Tryon 1871 inv Pompholycodeinae Lindholm 1927 Helisomatinae F C Baker 1928 Bayardellini Starobogatov Prozorova 1990 Planorbariini Starobogatov 1990 tribe Miratestini P F Sarasin 1897 synonyms Ferrissiinae Walker 1917 Ancylastrinae Walker 1923 Protancylinae Walker 1923 Physastrinae Starobogatov 1958 Ameriannini Zilch 1959 Patelloplanorbidae Franc 1968 tribe Plesiophysini Bequaert Clench 1939 subfamily Neoplanorbinae Hannibal 1912 synonym Payettiinae Dall 1924 subfamily Rhodacmeinae Walker 1917 2007 年本科部分物種的分類 Albrecht 等 2007 分析過本科部分物種，based on sequences of mitochondrial 18S ribosomal DNA and cytochromec oxidase I COI genes and on the basis of the results they rearranged the taxonomy like this Aclade sensu Albrecht et al 2007 Burnupia Walker 1912 Tribus Bulinini Bulinus O F Müller 1781 Indoplanorbis Annandale 1921 Tribus Ancylini RafinesqueSchmaltz 1815 Ancylus O F Müller 1774 Ferrissia Walker 1903 Gundlachia Pfeiffer 1849 Laevapex Walker 1903 Hebetancylus Pilsbry 1914 Bclade sensu Albrecht et al 2007 Glyptophysa Crosse 1872 Protancylus Sarasin 1897 Kessneria Walker Ponder 2001 Leichhardtia Walker 1988 Tribus Camptoceratini Planorbarius Duméril 1806 扁蜷族 Planorbini 多旋螺屬 Anisus Studer 1820 Bathyomphalus Charpentier 1837 旋螺屬 Gyraulus Charpentier 1837 Choanomphalus Gerstfeldt 1859 扁蜷屬 Planorbis O F Müller 1774 Tribus Segmentinini Segmentina 平扁蜷屬 Hippeutis 類扁蜷屬 Polypylis ，多脈扁螺屬 CClade sensu Albrecht et al 2007 Biomphalaria Preston 1910 Menetus H A Adams 1855 Planorbella Haldeman 1843 Planorbula Haldeman 1843 Cladogram The following is a cladogram that shows the phylogenic relationships within the Planorbidae according to Albrecht 2007 屬 本科的模式屬是 Planorbis 。以下列出主要根據布歇特及其他人 2005 的分類，因為 Albrecht 2007 的分類並未整全的包括本科所有的屬。至於每個屬的亞屬則依照 Glöer 2002 的文獻。以下綜合三份文獻的結果： 扁蜷亞科 Planorbinae Rafinesque 1815 多旋螺屬 Anisus S Studer 1820 subgenus Disculifer C Boettger 1944 Bathyomphalus Charpentier 1837 旋螺屬 Gyraulus Charpentier 1837 subgenus Torquis Dall 1905 subgenus Lamorbis Starobogatov 1967 subgenus Armiger Hartmann 1843 平扁蜷屬 Hippeutis Charpentier 1837：又名圓扁螺屬 tribe Ancylini Rafinesque 1815 Ancylus O F Müller 1773 type genus of tribe Ancylini tribe Biomphalariini H Watson 1954 Biomphalaria Preston 1910 type genus of tribe Biomphalariini Drepanotrema Crosse P Fischer 1880 扁卷螺族 Planorbini Rafinesque 1815 扁卷螺屬 Planorbis Müller 1773 tribe Planorbulini Pilsbry 1934 Planorbula Haldeman 1840 type genus of tribe Planorbulini tribe Segmentinini FC Baker 1945 Segmentina Fleming 1818 type genus of tribe Segmentinini 淤泥螺亞科 Bulininae P Fischer Crosse 1880 印度扁卷螺屬 Indoplanorbis Annandale Prashad 1920：單型屬，只有 Indoplanorbis exustus 一個物種 Liu L et al 2010 The phylogeography of Indoplanorbis exustus Gastropoda Planorbidae in Asia Parasites Vectors 3 57 。 Planorbarius Duméril 1806 Planorbella Haldeman 1842 Menetus H Adams A Adams 1855 subgenus Dilatata Clessin 1885 tribe Bulinini P Fischer Crosse 1880 Bulinus O F Müller 1781 type genus of subfamily Bulininae Gundlachia Pfeiffer 1849 tribe Coretini Gray 1847 Coretus Gray 1847 type genus of tribe Coretini tribe Miratestini P F Sarasin 1897 Miratesta P F Sarasin 1897 type genus of tribe Miratestini Amerianna Strand 1928 Ferrissia Walker 1903 Pettancyclus Iredale 1943 tribe Plesiophysini Bequaert Clench 1939 Plesiophysa P Fischer 1883 type genus of tribe Plesiophysini subfamily Neoplanorbinae Hannibal 1912 Neoplanorbis Pilsbry 1906 type genus of subfamily Neoplanorbinae subfamily Rhodacmeinae Walker 1917 Rhodacmea Walker 1917 type genus of subfamily Rhodacmeinae 亞科地位未定 other genera that are not yet sorted are listed here The genus Camptoceratops Wenz 1923 is no longer considered to be a planorbid It was recognised by Curry 1965 p 360 as a euthecosomatous pteropod Heterobranchia note by Arie W Janssen 092507 屬名 Taphius H Adams A Adams 1855 為 Biomphalaria 的異名。 Shell description The shells of most species in this family are disklike or buttonlike being coiled in one plane although several groups have shells that are more higherspired and some are limpetlike All coiled shell Planorbidae are sinistral in their shell coiling as is proved by their internal anatomy the respiratory and the genital orifice are situated on the left side however the animals carry their shells with what would normally be the ventral ie umbilical surface uppermost and because of this the shells appear to be dextral Indeed formerly planorbids were thought to have dextral shells and so species of this family were figured as if they had dextral shells Although it is now understood that these species are sinistral in shell coiling disklike Planorbid shells are often still shown in illustrations oriented as if they were dextral Most species of coiled planorbids have a rather thin and moderately smooth shell although more distinct sculpture such as a keel occurs in and is diagnostic of certain species In the flat keeled species the whorls tend to overlap The aperture has a sharp outer lip A peristome can be present but often the lip is not thickened nor reflected Those planorbid species which have a highspired shell may have a narrow umbilicus but frequently this is covered by callus In height most species vary between 6 mm and 6 cm however disklike shells are usually less than about 2 cm in maximum dimension Like all pulmonate aquatic snails ramshorn shells do not have an operculum to close the shell aperture Sinistral shells thumbleft 白化了的扁卷螺科物種，令帶有血紅素的身體組織在身體內顯得紅紅啡啡的。 Flatcoiled planorbid gastropod shells are hard to understand in terms of their coiling and orientation Many of the shells of species in this family are almost planispiral in coiling such that one side of the shell often looks rather like the other side but it is important to bear in mind that nonetheless there is an umbilical side and a spire side of the shell In addition these are in fact sinistral shells despite the fact that the snail carries its shell as if it were a normal dextral shell To make sense of the shell coiling the following facts are useful In life these pond snails hold their shells upside down compared to the normal gastropod shell orientation with the umbilicus facing upwards The spire of the shell is quite sunken in many species in addition it is carried facing downwards The umbilicus of the shell is very wide and shallow In some species the umbilicus is not as deeply dished as the sunken spire is so superficially it can be hard to tell one from the other However once it is understood that the planorbid shell is sinistral if the shell is held with the aperture on the left and facing the observer then the sunken spire side of the shell is uppermost This is a convenience for understanding the shell but is the opposite of the way the shell is actually carried in life The side of the shell which is in fact the spire a sunken spire faces down in the living animal contrary to what is the case in almost all other shelled gastropods Because the shell is carried upside down like this the aperture of the shell is angled to face downwards also so the aperture faces a little towards the spire not away from it as is usually the case in other shelled gastropods 血色素 相對於其他的軟體動物，扁卷螺科物種的血液都含有血紅素。因此，這些動物呼吸氧氣時都較其他軟體動物來得更有效；而血紅素亦令這些動物的身體帶紅色，這尤其在白化物種身上更明顯。 習性 扁卷螺科的大多數物種都只能在淡水生活，只有少數物種能存活於鹹淡水交界。所以對於其他未能存活於鹹淡水的物種，亦令農夫可以用食鹽來清除牠們。 Geological history Ancestors of ramshorn snails are known with certainty since the Jurassic period Modern taxa developed since the Cretaceous Geographical distribution Species in this family occur worldwide In Northwest Europe about 20 species are known including nonindigenous species In this region various extinct taxa are known to have occurred starting in the Jurassic period 參看 膀胱螺科 參考文獻 外部連結 NCBI Taxonomy Browser Planorbidae Systema naturae 2000 classification Taxon Planorbidae httpmkohl1netPlanorbidaehtml Frank Collins Baker The Molluscan Family Planorbidae The University of Illinois press Urbana 1945 B B