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Dissection and Flat-mounting of the Threespine Stickleback Branchial Skeleton
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パレオスペンディルスの形状は,四足類の祖先に親近さを示しています
Tatsuya Hirasawa1,2, Yuzhi Hu3, Kentaro Uesugi4
1Department of Earth and Planetary Science, Graduate School of Science, the University of Tokyo, Tokyo, Japan. hirasawa@eps.s.u-tokyo.ac.jp.
Nature
|May 25, 2022
まとめ
謎の化石であるPaleospondylus gunniは サルコプテリジアンであり 幹四足動物であったことが明らかになった. その独特な特徴は 四足類の根源にある 異質な進化を示唆し 進化の立場を明確にしています
科学分野:
- 古生物学
- 脊椎動物の進化
- 比較解剖学
背景:
- 1890年に発見されたパレオスペンジルス・ガンニは デヴォン期中期の謎の化石です
- 異様な形質的な特徴により,その系統的位置は不明のままである.
- 既知の脊椎動物の形態型とPaleospondylusを比較する難しさは,分類を妨げている.
研究 の 目的:
- パレオスペンジルス・ガンニの 遺伝的位置を明らかにするために
- 脊椎動物内のPaleospondylusの進化的関係を決定する.
- パレオスペンディルスの独特の形態の 発達と進化の影響を調査する
主な方法:
- 詳細な骨格分析のためにシンクロトロン放射線X線マイクロコンピュータトモグラフィー (SR-μCT) が使用された.
- 形態学的データを用いて,Palaeospondylusと既知の幹四足類を比較した系統分析が行われた.
- 骨組織学と細胞構造に焦点を当てた骨格要素の顕微鏡検査.
主要な成果:
- パレオスペンディルスはサルコプテリジアンで,おそらくは茎四足類である.
- その骨格は,縮した軟骨細胞の隙間,骨頭,および限られた周回性骨で構成されています.
- 神経頭蓋骨は,歯と皮膚の骨が欠けているにもかかわらず,EusthenopteronとPanderichthysに類似しており,Palaeospondylusを遺伝学的にそれらの間に置いています.
結論:
- パレオスペンディルスは 軟骨の骨格と 配列の付属体を含んだ 特徴のユニークな組み合わせを示しています
- これらの特徴は冠状四足類の幼虫にも見られ,発達の可塑性を示唆しています.
- この研究は,四足類の起源における予想外のヘテロクロニックな進化を明らかにし,Paleospondylusが重要な洞察を提供している.
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