雲南産の新しい肺魚化石が初期脊椎動物進化の重要段階を解明(New Fossil Lungfish from Yunnan Sheds Light on Critical Stage of Early Vertebrate Evolution)

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2025-12-17 中国科学院(CAS)

中国科学院(CAS)脊椎動物古生物学・古人類学研究所(IVPP)の朱敏教授率いる研究チームは、雲南省昭通市の前期デボン紀地層から新種のハイギョ化石 Paleolophus yunnanensis を発見した。本種は約4億1千万年前のもので、最初期のハイギョである Diabolepis と、後の真ハイギョ類をつなぐ長年不明だった形態学的空白を埋める存在である。全長25mmの三次元保存された頭骨は、CT解析により原始的特徴と派生的特徴を併せ持つことが示された。特に、顎関節構造は原始的な二重関節から真ハイギョ型頭骨への移行段階を捉えている。系統解析から本種はEudipnoiの基部に位置づけられ、ハイギョ進化が約400万年という短期間で急速に進んだことが示唆された。また北米産化石との類似性は、当時の南中国プレートと北米プレートの地理的近接を示す重要な証拠となる。

雲南産の新しい肺魚化石が初期脊椎動物進化の重要段階を解明(New Fossil Lungfish from Yunnan Sheds Light on Critical Stage of Early Vertebrate Evolution)
Skull of Paleolophus yunnanensis. (Image by Prof. ZHU Min’s team)

<関連情報>

新しい化石魚が初期の肺魚の急速な進化を明らかにする A new fossil fish sheds light on the rapid evolution of early lungfishes

Tuo Qiao ∙ Xindong Cui ∙ Wenjin Zhao ∙ … ∙ Jing Lu ∙ Brian Choo ∙ Min Zhu
Current Biology  Published:December 10, 2025
DOI:https://doi.org/10.1016/j.cub.2025.11.032

Highlights

  • New Pragian fossil from China reveals early lungfish anatomy
  • Lungfish key feeding traits evolved rapidly within ∼4 million years
  • Cranial specialization for durophagy drove early lungfish diversification
  • Analysis suggests Early Devonian biogeographic link between China and North America

Summary

Lungfishes, the closest living relatives of land vertebrates, have a long and conservative evolutionary history that began over 415 million years ago (mya) in the Early Devonian.1,2,3 Morphological gaps between the earliest known and most primitive lungfish, Diabolepis, and the more derived members of the group (Eudipnoi) hinder a comprehensive understanding of key evolutionary transformations near the onset of this lineage.1 A few early eudipnoans from the Pragian (∼410 Ma),4,5,6,7 such as Uranolophus from Wyoming, USA,8,9 have been thought to fill this gap, but their fossils are too flattened to reveal internal structures like the braincase.8,9,10,11 Here, we describe a new eudipnoan from the Pragian of China, whose skull is exceptionally well preserved, allowing us to study the inside of the head in detail for the first time in such an early lungfish. The new species has a palate similar to Uranolophus but also retains several features seen in Diabolepis. Phylogenetic and tip-dating Bayesian analyses place it at the base of the eudipnoan lineage, suggesting that lungfishes evolved rapidly during their early history. The discovery also points to connections between South China and North America during the Early Devonian. Altogether, this find helps clarify how early lungfishes developed key features that later shaped the group known today as the “living fossils.”12,13,14

生物工学一般
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