ニューメキシコのトリアシク期の恐竜形態の集合体と恐竜の興起
Randall B Irmis1, Sterling J Nesbitt, Kevin Padian
1Museum of Paleontology and Department of Integrative Biology, University of California, Berkeley, CA 94720-4780, USA. irmis@berkeley.edu
Science (New York, N.Y.)
|July 21, 2007
まとめ
古代のトライアス紀後期の動物から初期の恐竜への移行は,突然の絶滅ではなく,徐々に起こった. 化石によると,この恐竜の多様化には15~200万年かかり,地域によって変化していた.
科学分野:
- パレオントロジー・パレオントロジー
- ストラティグラフィー ストラティグラフィー
- 進化生物学の進化生物学について
背景:
- 現存する理論によると,初期の恐竜は競争による排斥や突然の絶滅によって,古代のトライアス紀後期の動物を急速に置き換えた.
- トライアス上期のチンル・フォーメーションからの化石証拠は,この移行を再評価する機会を提供します.
研究 の 目的:
- トライアス紀後期,特に恐竜の興起における動物界の移行の性質を調査する.
- 恐竜による古代のファウナの置き換えが突然だったか,徐々に起こったかを判断する.
主な方法:
- ニューメキシコ州上トリアシク・チンル・フォーメーションのヘイデン・クエリーからの化石アセンブリの分析.
- 地域の上トリアシックの化石集合の比較分析.
主要な成果:
- ヘイデン・クエリーと周辺のチンル・フォーメーションの化石は,急速な代替ではなく,段階的な移行を示しています.
- チンレの集合体で見つかった恐竜の親類は,以前は北米以外の古い層からしか知られていなかったグループを表しています.
- 恐竜の興起は1千5百万年から2000万年に及ぶ可能性がある.
結論:
- 恐竜の興起と古代のトライアス紀後期の動物群の衰退は,長期的かつ段階的なプロセスでした.
- この遷移は,おそらくダイアクロンであり,様々な古緯度において異なる時期に発生した.
- この発見は,トライアス紀の終わりに恐竜が急速に勢力を奪ったという長年にわたる考え方に異議を唱えている.
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