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''Xenoturbella'' is a genus of bilaterian animals; it contains two marine worm-like species. The first known species (''Xenoturbella bocki'') was discovered in 1915 by Sixten Bock but the first published description was only in 1949 by Einar Westblad.〔Westblad, E (1949) Xenoturbella bocki n. g., n. sp., a peculiar, primitive Turbellarian type. Arkiv för Zoologi 1:3-29〕 ==Taxonomy== The genus ''Xenoturbella'' contains two species: * ''Xenoturbella bocki'' * ''Xenoturbella westbladi'' Its taxonomic position has been considered enigmatic since its discovery. An early DNA analysis suggested a close relationship to molluscs (Noren & Jondelius, 1997), but turned out to have been contaminated with DNA from molluscs which ''Xenoturbella'' may have eaten (Bourlat ''et al.'', 2003; Israelsson & Budd, 2006). The genus is now the sole member of its own phylum Xenoturbellida (Haszprunar ''et al.'', 1991; Bourlat ''et al.'', 2006), and there is strong support from both morphological and molecular studies for a close relationship with Acoelomorpha.〔Lundin, K. (1998). The epidermal ciliary rootlets of Xenoturbella bocki (Xenoturbellida) revisited: new support for a possible kinship with the Acoelomorpha (Platyhelminthes). Zoologica Scripta, 27, 263–270.〕〔Raikova, O. I., Reuter, M., Jondelius, U., & Gustafsson, M. K. S. (2000). An immunocytochemical and ultrastructural study of the nervous and muscular systems of Xenoturbella westbladi (Bilateria inc. sed.). Zoomorphology, 120, 107–118.〕〔Hejnol, A., Obst, M., Stamatakis, A., Ott, M., Rouse, G. W., Edgecombe, G. D., et al. (2009). Assessing the root of bilaterian animals with scalable phylogenomic methods. Proceedings of the Royal Society, Series B, 276, 4261–4270.〕 A 2003 DNA study positioned ''Xenoturbella'' as a primitive deuterostome outside the established phyla (Bourlat ''et al.'', 2003). The deuterostome affiliations were recently corroborated by studies that indicate a basal position of this phylum within the deuterostomes〔Perseke M, Hankeln T, Weich B, Fritzsch G, Stadler PF, Israelsson O, Bernhard D, Schlegel M. (2007) "The mitochondrial DNA of ''Xenoturbella bocki'': genomic architecture and phylogenetic analysis". ''Theory Biosci''. 126(1):35-42. Available on-line at ()〕 or a sister group relationship with the echinoderms and hemichordates. However, some consider the evidence for a position within deuterostomes weak and favor the placement of ''Xenoturbella'' + Acoelomorpha more basally among Metazoa. 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「Xenoturbella」の詳細全文を読む スポンサード リンク
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