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Spiralia
The Spiralia are a morphologically diverse clade of animals, including within their number of molluscs, annelids, platyhelminths and other phyla. The Spiralian clade of animals are more commonly referred to as the Lophotrochozoa, although whether these two terms are equivalent is debated, as noted further below. More uncontroversially, the term ''Spiralia'' is applied to those phyla that exhibit canonical spiralian cleavage. Spiral cleavage, from which this group draws its name, is a pattern of early development found in most (but not all) members of the Lophotrochozoa. ==Distribution of spiralian development across phylogeny==
Members of the molluscs, annelids, platyhelminths and nemerteans have all been shown to exhibit spiral cleavage in its classical form. Other Lophotrochozoan phyla (rotifers, brachiopods, phoronids, gastrotrichs, and bryozoans) are also said to display a derived form of spiral cleavage in at least a portion of their constituent species, although evidence for this is sparse.
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「Spiralia」の詳細全文を読む
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