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''Spyroceras'' is pseudorthocerid genus from the Devonian of North America and Europe, defined by Hyatt in 1884. Pseudorthocerids are a kind of orthocertaoid, a taxonomic group within the Nautiloidea. Specifically ''Spyroceras'' belongs to the pseudorthocerid family, Spyroceratidae. ''Spyroceras'' had annulated orthocones with straight transverse sutures, transverse or slightly oblique surface annulations, and faintly cyrtoconic apeces. Surface ornamentation varies but longitudinal lirae are conspicuous from earliest stage. The siphuncle was central or slightly offset ventrally, and composed of expanded segments typical of the Pseudorthocerida. Cameral and siphonal deposits developed later than in most pseudorthocerids and are thus confined to the apical portion of the phragmocone. ==References== * Sweet, W.C. 1964. Nautiloidea -Orthocerida. Treatise on Invertebrate Paleontology, Part K. Geological Soc. of America and Univ of Kansas press. *(''Spyroceras'' Paleobio db ) *(Sepkoski List - Cephalopoda ) 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「Spyroceras」の詳細全文を読む スポンサード リンク
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