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''Hoeloceras'' is an extinct orthoconic nautiloid cephalopod from the upper Ordovician, generally included in the Actinocerida. Nautiloids are a subclass of shelled cephalopods that were once diverse and numerous but are now represented by only a couple of genera, ''Nautilus'' and ''Allonautilus''. ''Hoeloceras'', which has a straight shell with a broadly curved to almost flattened venter on the underside and a more highly arched dorsum on the upper, meeting acutely on either side, was named by Walter Sweet in 1958 (Chen & Liu 1977, Teichert 1964) who first recognized it in Ordovician sediments near Oslo, Norway, and included it in the Actinocerida. Teichert (1964) identified ''Hoeloceras'' as a synonym of ''Lambeoceras'', as the acutely angled dorso-ventral seam suggests. Flower (1968) referred to ''Hoeloceras'' as a "flatfish", in common with ''Lambeoceras'' and ''Gonioceras'', but reassigned it to the Reudemannoceratidae (Discosorida) noting that neither (siphuncular) annuli or parispatium - diagnostic of the Actinocerida - had been observed. Since then specimens identified as ''Hoeloceras'', and retained in the Actinocerida, have been discovered in China (Chen& Liu) and Korea (Yun, Cheol-Soo), where, in Korea, it is associated with the actinocerids, ''Armenoceras'', ''Ormoceras'', and ''Selkirkoceras''. == See also == List of nautiloids 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「Hoeloceras」の詳細全文を読む スポンサード リンク
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