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The Trigonocerataceae is a superfamily within the Nautilida that ranged from the Devonian to the Triassic that is thought to have contained the source for the Nautilaceae in which ''Nautilus'' is found. Trigonocerataceae are characterized by open-spiraled, gyroconic, to closed, nautiliconic shells in which the whorl section is quadrate in primitive forms; the venter typically narrow to acute, the dorsum broad. In some advanced forms the venter may become concave or broad and rounded and In some the surfaces may be strongly lirate. ==Classification and phylogeny== The Trigonocerataceae is based on the Family Trigonoceratidae of Hyatt, 1884, with which other phylogenetically related families are combined, and is equivalent to the abandoned Centroceratida of Flower in Flower and Kümmel 1950, and to the Centroceratina of Shimanskiy 1957, revised to the Centrocerataceae, Shimanskiy 1962. The Trigonocerataceae combines five families, the type, Trigonoceratidae, along with the Centroceratidae, Grypoceratidae, Permoceratidae, and Syringonautilidae. Phylogenetic study and age shows that the Centroceratidae are the root stock in spite of having been first recognized 16 years after the Trigonoceratidae were first described. The Centroceratidae gave rise to the Trigonoceratidae and Grypoceratidae in the Early MIssissippian while continuing until the very early Permian. The Trigonoceratidae which ranged into the Permian left to descendants. The Grypoceratidae which ranged almost to the end of the Triassic gave rise to two small families, the Permian Permoceratidae and the Triassic Syringonautilidae. The Syringonautilidae, in turn, is the source for the Nautilidae (Nautilaceae) which contains the genus Nautilus. 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「Trigonocerataceae」の詳細全文を読む スポンサード リンク
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