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コノドントの起源と脊椎動物の鉱化骨格の起源
Duncan J E Murdock1, Xi-Ping Dong, John E Repetski
1School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK.
Nature
|October 18, 2013
まとめ
早期ののない脊椎動物であるコノドントは,鉱化組織の段階的な進化を示しています. この研究は,歯がの後に収束経由で進化したことを示唆し,内側から外側への仮説を否定する.
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:
- コノドントは最古の脊椎動物の鉱化骨格を有しており,歯との進化に関する理論に影響を与えました.
- 以前の仮説は",内側から外へ"の理論のように,派生コノドント (ユーコノドント) に依存していた.
研究 の 目的:
- ユーコノドントのパラコノドントの祖先を調査するために.
- パラコノドントとユーコノドントの微細構造の違いと類似性を比較する.
- パラコノドントとユーコノドントの進化的関係に関する議論を解決するために.
主な方法:
- シンクロトロン放射線X線トモグラフィー顕微鏡 (SRXTM).
- コノドントの要素の微細構造的特徴.
- パラコノドントとユーコノドントの組織と成長パターンの比較分析.
主要な成果:
- パラコノドントは,ユーコノドントの基礎体と似た組織と成長パターンを含む,さまざまな構造的差異を示す.
- これは,ユーコノドントの特徴の段階的な獲得を示しています.
- ユーコノドントの冠組織と脊椎動物のエナメルとのホモロジーは,独立で収束する進化のために拒否されます.
結論:
- コノドントの要素と脊椎動物のオドントードの類似性は,収束の結果である.
- コノドントとの脊椎動物の最後の共通の祖先には,鉱物化した骨格組織が欠けていた可能性が高い.
- "内側から外へ"の仮説と,歯がの前に進化したという考えは否定される.
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