Gryphaea

…There are several ancient organisms that have long been considered good examples of orthotopic evolution. Orthotopic evolutionists say that the Jurassic oyster Gryphaea was driven to extinction by its excessively curled shell beyond its usefulness, and that the giant horned deer of the Ice Age and the saber-toothed tiger (Smilodon), with their extremely developed upper canines, are also products of non-adaptive evolution and cannot be explained by the theory of natural selection. However, recent research has been negative about both interpretations. For example, it has been revealed that Gryphae evolved in the opposite direction, becoming looser, due to a more comprehensive fossil record, and that the horns of the giant horned deer were the result of sexual selection, and the canines of the saber-toothed tiger have been examined mechanically and are now explained as having a functional meaning. …

*Some of the terminology that mentions "Gryphaea" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…古くから定向進化の好例とされてきた古生物がいくつかある。定向進化論者は，ジュラ紀のカキ類グリフェアGryphaeaは有用の限界を越えて過剰に殻が巻き絶滅に追いこまれたとし，氷河期の巨大な角をもつオオツノジカ，上顎の犬歯が極度に発達した剣歯虎（けんしこ）(スミロドン)も非適応的進化の産物であって，自然淘汰説では説明できないとした。しかし，最近の研究はいずれもその解釈には否定的で，例えばグリフェアはより充実した化石記録によって逆に巻きがゆるむ方向に進化したことが明らかにされたし，オオツノジカの角は性淘汰で，剣歯虎の犬歯は力学的に検討されて機能的な意味があると説明されるようになった。…

※「Gryphaea」について言及している用語解説の一部を掲載しています。

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