最古の関節のあるコンドリヒチアンは,初期デボニアン期に由来する
Randall F Miller1, Richard Cloutier, Susan Turner
1Steinhammer Palaeontology Laboratory, New Brunswick Museum, Saint John, New Brunswick E2K 1E5, Canada. millerrf@nb.aibn.com
Nature
|October 3, 2003
まとめ
4億900万年前の状サメ,ドリオドゥス・プロブレマティカス (Doliodus problematicus) の発見は,初期のコンドリヒチアンの洞察力を提供している. この化石は,ペアリングされた胸の finn-spinesを明らかにし,以前は軟骨魚では知られていなかった特徴です.
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
- イクチオロジー イクチオロジー
背景:
- サメを含むコンドリヒチア類は,オルドビキア期後期に遡る化石記録を持っています.
- 知られている最も古い関節の遺骸は,初期デヴォン期に由来する.
- Doliodus problematicusは以前は孤立した歯からしか知られていなかったので,その分類は議論の余地があった.
研究 の 目的:
- 極めて保存状態が良好な関節型のサメの化石の発見を報告する.
- 早期の進化とコンドリクシア類と基礎の脊椎動物の相互関係を解明する.
- Doliodus problematicusの分類的地位を調査するために.
主な方法:
- 化石を含む層の地質年代測定.
- 歯,頭蓋骨,の構造を含む,関節のある化石の詳細な形態学的分析.
- 他の初期の脊椎動物化石との比較解剖学的研究.
主要な成果:
- カナダの初期デボニアン時代の4億900万年前の状サメ,ドリオドゥス・プロブレマティカス (Doliodus problematicus) の発見
- この標本は,インシトゥの歯の家族を持つ最も古いサメであり,最も古いコンドリヒチアンの脳骨の1つである.
- 化石は,軟骨魚の新鮮な特徴であるペアリングされた胸の finn-spinesを展示しています.
結論:
- Doliodus problematicusは,初期のサメの進化における重要な移行形態を表しています.
- ペアリングされた胸の finn-spinesの存在は,初期のコンドリクシアの解剖学の以前の理解を挑戦します.
- この発見は,基礎の脊椎動物の多様化に関する私たちの知識を高めます.
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