Also called antheroids. A group of ammonites in the order Ceratitida that showed remarkable adaptive radiation during the Triassic Period and developed into a wide variety of species. The representative genus is Ceratites , and it is important as an index fossil. The sutures are unique, with a mountain in the center of the valley on the ventral side, and the valley on the dorsal side is usually spatula-shaped with two branches at the tip. Some have almost no small indentations, some only have them at the valley bottom, some have mountains, and some are complex and multi-branched. They are found in various parts of the Indian and Pacific regions, and in Japan in Miyagi Prefecture, Tokushima Prefecture, Kumamoto Prefecture, Okinawa Prefecture, and other places. Source: Heibonsha World Encyclopedia, 2nd Edition Information |
菊面石類ともよばれる。アンモナイト類の中で三畳紀に著しい適応放散を示し,多種多様の分化発達をなしたセラタイト目Ceratitidaのこと。代表属はセラティテスCeratitesで,示準化石として重要である。縫合線に独特の特徴が見られ,腹面の谷の中央に山があり,背面の谷は通例へら状で先端が二分している。小刻みがほとんどないものから,谷底だけにあるもの,山にも及ぶもの,複雑化し多分岐したものがある。インド,太平洋地域の各地で産出するが,日本でも宮城県,徳島県,熊本県,沖縄県などから産出する。
出典 株式会社平凡社世界大百科事典 第2版について 情報 |
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