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''Strepsodiscus'' is an extinct genus of very primitive fossil snail-like molluscs from the early part of the Late Cambrian (Dresbachian Age) of North America. The coiled, slightly asymmetrical shells are about 3 cm in height. It is not known whether these are shells of gastropods (sea snails) or monoplacophorans, which are more primitive mollusks. Bouchet & Rocroi (2005)〔Bouchet P. & Rocroi J.-P. (Ed.); Frýda J., Hausdorf B., Ponder W., Valdes A. & Warén A. 2005. ''Classification and nomenclator of gastropod families''. Malacologia: International Journal of Malacology, 47(1-2). ConchBooks: Hackenheim, Germany. ISBN 3-925919-72-4. ISSN 0076-2997. 397 pp. http://www.vliz.be/Vmdcdata/imis2/ref.php?refid=78278〕 divide the Bellerophontoidea into 8 families listed Paleozoic molluscs with isostrophically coiled shells of uncertain position within Mollusca (Gastropoda or Monoplacophora) Knight, et al., 1960 included this genus within the Cyrtolitidae, a paraphyletic or polyphyletic assemblage of proto-gastropods and Tergomyan molluscs. ''Strepsodiscus'' may be too primitive to be a true gastropod. ==Species== Species within the genus ''Strepsodiscus'' are as follows: () * ''Strepsodiscus major'' * ''S. minutissimus'' * ''S. paucivoluta'' * ''S. splettstoesseri'' * ''S. strongi'' 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「Strepsodiscus」の詳細全文を読む スポンサード リンク
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