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The heart urchins or Spatangoida are an order of sea urchins. Their body is a somewhat elongated oval in form, and is distinguished by the mouth being placed towards one end of the animal, and the anus towards the other. As a result, heart urchins, unlike most other sea urchins, are bilaterally symmetrical, and have a distinct anterior surface. The presence and position of the mouth and anus typically give members of this group the distinct "heart" shape from which they get their name. Heart urchins have no feeding lantern, and often have petaloids sunk into grooves. They are a relatively diverse order, with a number of varying species. ==Taxonomy== According to World Register of Marine Species : * sub-order Brissidina Stockley, Smith, Littlewood, Lessios & MacKenzie-Dodds, 2005 * * family Asterostomatidae Pictet, 1857 * * family Brissidae Gray, 1855 * * family Palaeotropidae Lambert, 1896 * * super-family Spatangidea Fischer, 1966 * * * family Eupatagidae Lambert, 1905 * * * family Eurypatagidae Kroh, 2007 * * * family Loveniidae Lambert, 1905 * * * family Macropneustidae Lambert, 1905 * * * family Maretiidae Lambert, 1905 * * * family Megapneustidae Fourtau, 1905 † * * * family Spatangidae Gray, 1825 * family Hemiasteridae H. L. Clark, 1917 * sub-order Micrasterina Fischer, 1966 * * family Aeropsidae Lambert, 1896 * * family Micrasteridae Lambert, 1920a * family Palaeostomatidae Lovén, 1868 * sub-order Paleopneustina Markov & Solovjev, 2001 * * super-family Paleopneustidea A. Agassiz, 1904 * * * family Paleopneustidae A. Agassiz, 1904 * * * family Pericosmidae Lambert, 1905 * * family Prenasteridae Lambert, 1905 * * family Schizasteridae Lambert, 1905 * family Somaliasteridae Wagner & Durham, 1966a † * family Toxasteridae Lambert, 1920a † 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Spatangoida」の詳細全文を読む スポンサード リンク
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