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Jurassic flightless bird reveals early ecological diversity of avialans

Published: 10/14/2026, 12:00 AM

Nature volume 658, pages 690–697 (2026) Cite this article The origin and early diversification of birds remain highly debated in vertebrate evolution. Although estimates of the evolutionary timescales suggest a Jurassic period radiation1,2, a profound scarcity of fossils from this period has hampered how the distinctive bird bauplan was assembled3,4,5. Selection for powered flight has been viewed as the primary driver of early avialan skeletal modifications3,6,7, attesting to the independent occurrences of aerodynamic features among paravian lineages8. Here we report on the discovery of a Late Jurassic avialan, Yuezhuornis yangyuanensis, gen. et sp. nov., from the Zhenghe Fauna of southeastern China9. As one of the earliest diverging avialans, Y. yangyuanensis exhibits a striking mosaic of features, combining a mixture of avialan- and troodontid-like cranial characters, paired with derived postcranial traits and a deinonychosaur-like hyperextensible second pedal digit. Phylogenetically informed analyses show that Y. yangyuanensis possesses markedly short forelimbs—a condition present widely among non-avialan theropods. These findings provide strong evidence for a terrestrial, flightless lifestyle of Y. yangyuanensis. Our study demonstrates that evolution works intensively as exemplified by the occurrence of several, divergent ecological pathways being exploited in the initial diversification of birds. This is a preview of subscription content, access via your institution Access Nature and 54 other Nature Portfolio journals Get Nature+, our best-value online-access subscription Prices may be subject to local taxes which are calculated during checkout The specimen (IVPP V34427) described in this study is archived and available on request from the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China. All data, including the measurements and phylogenetic data matrix that support the findings of this study are included as Supplementary Information. Raw data used in phylogenetic and morphometric analyses are available at Figshare (https://doi.org/10.6084/m9.figshare.31228414)83. The Life Science Identifier for Y. yangyuanensis is urn:lsid:zoobank.org:act: DE4454F3-9E3C-4D21-AE64-599B2A2D0013. R code and MrBayes commands used in phylogenetic and morphometric analyses are available at Figshare (https://doi.org/10.6084/m9.figshare.31228414)83. Lloyd, G. T., Bapst, D. W., Friedman, M. & Davis, K. E. Probabilistic divergence time estimation without branch lengths: dating the origins of dinosaurs, avian flight and crown birds. Biol. Lett. 12, 20160609 (2016). Article PubMed PubMed Central Google Scholar