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''Callaionautilus'' is a cephalopod genus included in the nautilid family Clydonautilidae that lived during the Late Triassic. Its fossils have been found on the island of Timor. The shell of ''Callaionautilus'' is involute, coiled such that only the outer whorl is exposed. Early whorls have nodes on the ventral shoulder that disappear toward the aperture. Later whorls have a nodose keel bordered by furrows. The siphuncle position is unknown. ''Clydonautilus'', ''Cosmonautilus'', ''Proclydonautilus'', and ''Styrionautilus'' are closely related genera belonging to the same family. ==References== * Bernhard Kummel, 1964. Nautiloidea-Nautilida. Treatise on Invertebrate Paleontology, Part K. Geological Society of America. * (''Callaionautilus'' ) in Fossilworks gateway. 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「Callaionautilus」の詳細全文を読む スポンサード リンク
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