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Arietitidae is a family of true ammonites that make up part of the superfamily Psilocerataceae. They comprise medium-size to large or gigantic genera which in general are strongly ribbed, tuberculate in some, with keeled or grooved and keeled venters, and well differentiated ammonitic sutures. The aptycus is single valved with a shiny, concentrically striated surface. Arietitidae dominated Lower Jurassic, Sinemurian ammonites, worldwide, extending into the lower Pliensbachian. The Arietitidae may have their origin in the Schlotheimiidae if not directly from the Psiloceratidae, and is the probably source for the Oxynoticeratidae. ==References== * * Donvan, D.T. and Callomon, J.H. 1981, Classification of the Jurassic Ammonitina., in The Ammonoidea, The Systematics Association Special Volume 18. 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「Arietitidae」の詳細全文を読む スポンサード リンク
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