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Pachydiscidae comprise a family of middle and upper Cretaceous ammonites (order Ammonitida) which makes up part of the Desmocerataceae. Pachydiscidae are of moderate to large size, evolute to rather involute, and vary in section from inflated and depressed to high-whorled and compressed. They are distinguished from the Desmoceratidae by strong ribbing at some growth stage, that normally crosses the venter uninterrupted, and by the tendency to develop strong tuberculation, at least on the umbilical shoulder. The Pachydischidae are derived from the Desmoceratidea, in the upper Albian, about the same time as the Kossmaticeratidae, but extend further into the Maastrichtian, virtually to the end of the Cretaceous. ==Genera== * ''Anapachydiscus'' † Yabe and Shimizu 1926 * ''Baskaniceras'' † Wright and Kennedy 1984 * ''Canadoceras'' † Spath 1922 * ''Eupachydiscus'' † Spath 1922 * ''Lewesiceras'' † Spath 1939 * ''Menuites'' † Spath 1922 * ''Nowakites'' † * ''Pachydiscus'' † Zittel 1884 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「Pachydiscidae」の詳細全文を読む スポンサード リンク
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