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Kochoceras
''Kochoceras'' is an extinct nautiloid genus from the later Ordovician belonging to the family Actinoceratidae and found in North America.
==Morphology==
''Kochoceras'' is relatively short, breviconic, and grew to be fairly large with a shell more rapidly expanding than in ''Actinoceras''.
The ventral, or under, side is strongly flattened with prominent lobes that may give the impression of ''Lambeoceras''. However septa in ''Kochoceras'' are more widely spaced and the siphuncle, which is proportionally very large, is in broad contact with the ventral wall. The siphucle in ''Lambeoceras'' is proportionally much smaller and is removed about one diameter from the ventral wall. The diameter of the siphuncle in the apical part of ''Kochoceras'' is 3/4 or more that of the shell.
The siphuncle of ''Kochoceras'' is similar to that of ''Actinoceras'', the main difference between the two being that ''Kochaceras'' is breviconic (short) and has a narrow stratigraphic range, while ''Actinoceras'' is longiconic, lengthy, and has a stratigraphic range that extends through the Middle- and Upper Ordovician.〔Flower R.H. 1957. Studies of the Actinoceratida, New Mexico Bureau of Mines and Mineral Resources Memoir 2, Socorro NM.〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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