古代翼竜が飛行能力を急速に進化させたことを示す研究(Study: Ancient pterosaurs rapidly evolved for flight)

2025-12-04 ジョンズ・ホプキンス大学(JHU)

新しい国際研究チームは、プテロサウルス(翼竜)が、現生の鳥やコウモリとは異なり、 出現直後にほぼ完成された「飛行能力」を獲得した可能性が高いと報告した。彼らは化石の頭蓋骨を高解像度CTなど3Dイメージングで分析し、脳の形状・構造を再構築。特に視覚を司る視蓋葉(optic lobe)の拡大や、小型ながらも飛行に必要な神経解剖学的特徴が備わっていたことを確認した。これらは、翼竜の最も近縁な非飛行古爬虫類である木上性獣弓類(例: Lagerpetid)との比較により、飛行獲得までに段階的脳の大型化を要した鳥類とは異なり、**「出現直後の急速な飛行獲得(バースト進化)」**の可能性を示すものとされた。この結果は、飛行の進化における多様な進化経路と生物学的法則の再考を促す。

<関連情報>

飛行の進化における翼竜と非鳥類原鳥類の神経解剖学的収束 Neuroanatomical convergence between pterosaurs and non-avian paravians in the evolution of flight

Mario Bronzati ∙ Akinobu Watanabe ∙ Roger B.J. Benson ∙ … ∙ Ingmar Werneburg ∙ Sterling J. Nesbitt ∙ Matteo Fabbri
Current Biology  Published:November 26, 2025
DOI:https://doi.org/10.1016/j.cub.2025.10.086

古代翼竜が飛行能力を急速に進化させたことを示す研究(Study: Ancient pterosaurs rapidly evolved for flight)

Highlights

  • The most complete cranial endocast of a lagerpetid, a pterosaur precursor, is reported
  • Lagerpetids have laterally positioned optic lobes like pterosaurs and bird precursors
  • Pterosaurs show brain anatomy resembling bird precursors but not modern birds
  • Pterosaur brain evolution lacks the exaptation pattern seen in the bird lineage

Summary

The oldest known pterosaurs lived approximately 220 million years ago1 and were already animals capable of powered flight,2 an ability that later evolved independently among paravian dinosaurs, the group that includes living birds and their closest non-avian relatives.3 Flight is a complex locomotory mode that requires physiological adaptations4 and a dramatic transformation of the body plan, including changes in body proportions, specialized integument, and acquisition of novel neurosensory capabilities.5 Although pterosaurs and birds developed distinct skeletal and integumentary adaptations for flight, they are hypothesized to share neuroanatomical traits linked to aerial locomotion.6,7,8,9 Here, we use geometric morphometrics and phylogenetically informed analyses to assess the origin and evolution of brain shape and size in pterosaurs, tracing the transformation from their non-volant closest relatives (lagerpetids), and compare their trajectory with that in the dinosaur-bird transition. Pterosaurs have globular brains with moderately enlarged hemispheres, more closely resembling non-avian paravians such as troodontids and Archaeopteryx lithographica than living birds. Whereas birds inherited their basic brain structure from their dinosaurian ancestors,10,11,12,13,14,15,16,17 pterosaurs share only the ventrolateralization of the optic lobe with their closest non-volant relatives, the lagerpetids. This suggests that, in contrast to the bird-line archosaurs, where exaptation may have played a central role in the stepwise assembly of the avian brain configuration, brain evolution in pterosaurs seems to have unfolded rapidly at the origin of flight.

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