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Pseudactinoceras : ウィキペディア英語版 | Pseudactinoceras
''Pseudactinoceras'' is an extinct nautiloid cephalopod included in the order Pseudorthocerida and the namesake of the family Pseudactinoceratidae (Sweet, 1964). ==Description== ''Pseudactinocras'' are slightly depressed longiconic cyrtocones with a large siphuncle located between the center and ventral margin. Early siphuncle segments, in the juvenile phragmocone are suborthochoantic; later segments, in the mature phragmocone, become cyrtochoantic, nummuloidal, broader than long. Parietal deposits lining the interior of the siphuncle grow more prominently forward than backward, with canals slightly anterior of segment centers. Thick cameral deposits develop ventrally, but are only thin dorsally (Sweet, 1964).
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「Pseudactinoceras」の詳細全文を読む
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