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''Ptychodus mortoni'' was a shark believed to be about 10 m long that probably crushed and ate large shelled animals such as giant clams. The bivalves that lived during this time included gigantic animals, possibly having extremely thick shells, such as the inoceramids (''Volviceramus'', ''Platyceramus'', etc...). Given its large size, though, this species of ''Ptychodus'' might also have eaten ammonites and primitive turtles, like ''Desmatochelys''. It is believed to have been a sluggish bottom-dwelling shark, rather than an actively fast swimmer. It lived about 89 million years ago (Turonian stage). Therefore, while only large numbers of its teeth, and jaw fragments are known, it might've resembled a massive nurse shark or a sand tiger shark. Fossils have been found in the Western Interior Seaway, Kansas, USA.〔(BBC: Giant predatory shark fossil unearthed in Kansas )〕 ==References== 〔 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「Ptychodus mortoni」の詳細全文を読む スポンサード リンク
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