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''Simardoceras'' is a genus in the discosorid (nautiloid cephalopod) family Westonoceratidae from the Middle Ordovician of Quebec. The shell of ''Simardoceras'' is a moderately expanding exogastric cyrtocone, said to resemble a rather large ''Oncoceras'', but with a siphuncle that is definitely discosorid. The venter is almost uniformly convex in longitudinal profile. The dorsal profile changes from concave in the apical portion to straight, then slightly convex at the front of the phragmocone and back of the body chamber, the concave again near the aperture. The siphuncle is ventral. Segments are subquadrate in outline and are longer than broad. Connecting rings are thick. Although ''Simardoceras'' somewhat resembles ''Winnipegoceras'' is the form of its siphuncle, it differs in its very broad cross section. The slender siphuncle segments also distinguish it from the apparently more closely related ''Sinclairoceras'' and from its apparent derivative ''Reedsoceras''. ''Sinclairoceras'', ''Simardoceras'', and ''Reedsoceras'' are found in beds of Black River age (Middle Ordovician) and seem to be closely related, and may even form a phylogenetic (evolutionary) series. ==References== * Flower, R.H. and Curt Teichert, 1957. The Cephalopod Order Discosorida. University of Kansas Paleontological Contributions, Mollusca, Article 6. July 1957 * Teichert, C 1964. Nautiloidea -Discosorida. Treatise on Invertebrate Paleontology Part K. Geological Soc of America and Univ. Kansas Press 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「Simardoceras」の詳細全文を読む スポンサード リンク
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