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''Eburoceras'' is an early nautiloid cephalopod from the Upper Yenchau and Wanwankau, Upper Cambrian Trempealeauan of China, assigned to the Ellesmeroceratidae. The shell of ''Eburoceras'' is long and narrow, curved in a broad arc of near constant curvature, interpreted as endogastric, assuming the small siphuncle on the inner margin to be ventral. Known for sure dorsal siphuncles don't appear until later in the Early Ordovician with the Trocholitidae, which if so would make it (''Eburoceras'')exogastric. ''Eburoceras'' is the most strongly curved of the Cambrian ellesmeroceratids. Eburoceras is the earliest ellesmeroceratid except for the short lived ''Hunyuanocers'', from the lower part of the Upper Yenchou, that proceeded it. ''Eburoceras'' died out at the end of Wanwankau time, along with the other Late Cambrian ellesmeroceratid genera, except for ''Ectenolites'' and ''Clarkoceras'', which persisted into the Ordovician. Late Cambrian ''Tanycamerocers'' (Ellesmeroceratidae) is similar in being long and narrow and having a small marginal siphuncle, but is straight. Late Cambrian ''Huaiheceras'' (Hauiheceratidae) is also similar in being long with a small marginal siphuncle, but is exogastric and less strongly curved. ==References== * Chen Jun-yuan & Curt Teichert. Cambrian Cephalopods. Geology v.11 Nov. 1983 * Curt Teichert. Main features of Cephalopod Evolution. the Mollusca Volume 12. Paleontology and Neontology of Cephalopods. Academic Press Inc. 1988. 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「Eburoceras」の詳細全文を読む スポンサード リンク
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