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中国産の無魚の化石は,初期ののある脊椎動物の解剖学を予兆している
Zhikun Gai1, Philip C J Donoghue, Min Zhu
1School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK.
Nature
|August 19, 2011
まとめ
化石のガレアスピドは,重要な頭蓋骨の特徴がより前に進化したことを示しています. の進化そのものではなく,脊椎動物の頭蓋骨の段階的な再編成は,脊椎動物のの発達に道を開いた.
科学分野:
- パレオントロジー・パレオントロジー
- 進化生物学の進化生物学について
- 比較解剖学 比較解剖学とは
背景:
- の脊椎動物 (gnathostomes) は現代の生態系を支配しているが,その進化的起源,特に頭蓋骨の再編成は不明である.
- 生きているのない脊椎動物 (サイクロストーム) は,初期の脊椎動物の頭蓋骨の進化について,限られた洞察を提供している.
- 絶滅した"オストラコダーム"は,を持つ脊椎動物への移行を理解するために極めて重要です.
研究 の 目的:
- 骨のあるのない脊椎動物の古代集団であるgaleaspidsの頭蓋骨の解剖学を調査するために.
- の起源に先立つ脊椎動物の頭蓋骨の再編成における進化のステップを理解するために.
- の発達の前提条件に関する発達モデルをテストする.
主な方法:
- シンクロトロン放射線X線トモグラフィーは,ガレアスピッドの頭蓋骨の解剖学を分析するために使用されました.
- 鼻袋と下垂体管の位置を比較分析した.
- この発見は,現存するサイクロストームやオステオストラカン,そしてグナトストームと比較した.
主要な成果:
- ガレアスピドは,鼻袋と前面に開いている下垂体管を並べた鼻袋を横横に持っていた.
- ゲールアスピドのこれらの構造は独立しており,グナトストームに似ているが,サイクロストームやオステオストラカンとは違っていた.
- この独立した状態は,現在のモデルによると,の発達の前提条件です.
結論:
- 脊椎動物の頭蓋骨の再編成は,の進化によってのみ引き起こされるのではなく,段階的に起こりました.
- ゲールアスピドの観察された頭蓋骨の解剖学は,漸進的な進化過程を示しています.
- この段階的な再編成は,グナトストームの頭部構造の後の発展を容易にした.
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