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The Trachyceratidae is a family of ceratitid ammonoid cephalopods that lived during the Middle- and Late Triassic characterized by shells that are more or less involute and highly ornamented. Trachyceratid shells have their whorl sides covered with flexious ribs that are usually tuberculate. The venters generally have a median furrow bordered by rows of tubercles or continuous keels. The Trachyceratidae makes up part of the superfamily Clydonitaceae along with such families as the Clydonitidae and Arpaditidae. The Clydonitaceae is also known by the junior synonym Trachycerataceae. ==''References''== * Arkell et al. Mesozoic Ammonoidea. Treatise on Invertebrate Paleontology, Part L. 1957 * Bernhard Kummel 1952. A Classification of Triassic Ammonoids. Jour of Paleontology, Vol 26, No.5, pp 847-853, Sept 1952 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「Trachyceratidae」の詳細全文を読む スポンサード リンク
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