古生物学:初期の脊椎動物の軟骨の化
Philippe Janvier1, Marius Arsenault
1CNRS, UMR 8569, Muséum National d'Histoire Naturelle, 75231 Paris Cedex 05, France. janvier@mnhn.fr
Nature
|June 7, 2002
まとめ
古代ののない魚,Euphanerops longaevusは,現代のハグフィッシュやランプレイとは異なり,軟骨を化していた. この発見は,脊椎動物の鉱化骨格の早期の平行進化を示唆している.
科学分野:
- パレオントロジー・パレオントロジー
- 脊椎動物の進化について
- バイオミネラライゼーション
背景:
- のない脊椎動物であるハグフィッシュとランプレイは,大きなコンドロサイトを持つ非カルシファイド軟骨を持っています.
- 現代のの脊椎動物は,コラーゲンで強化された,化した軟骨を示しています.
- 脊椎動物の骨格鉱化による進化の経路は,まだ完全に理解されていない.
研究 の 目的:
- 古代ののない魚,Euphanerops longaevus.の骨格組成を調べるために
- E. longaevusの軟骨構造と鉱化を,現存するのない脊椎動物とのある脊椎動物と比較するために.
- 初期の脊椎動物における内 Skeleton 鉱化の進化軌道を推論する.
主な方法:
- Euphanerops longaevus.の化石化した軟骨の顕微鏡検査
- 化石化した軟骨内の細胞組織とミネラル含有量の分析.
- 現代の脊椎動物の軟骨からの組織学的データとの比較分析.
主要な成果:
- 3億7千万年前のエウファネロプス・ロンガエブス (Euphanerops longaevus) は,広く化した軟骨を持っていた.
- E. longaevusの軟骨の細胞構造は,現代のランプレイの細胞構造 (非鉱物化) に似ていた.
- このカルシフィケーションパターンは,現代ののある脊椎動物に見られるものとは大きく異なる.
結論:
- 初期ののない魚は,E. longaevusのように,軟骨の化という独特な形態を示した.
- これは,のある脊椎動物に至る系統とは無関係な,鉱化性内骨格への潜在的な並列進化の経路を表しています.
- この発見は,早期の脊椎動物進化における骨格発達の多様な戦略を明らかにした.
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