Powered flight evolved independently in vertebrates in the pterosaurs, birds and bats, each of which has a different configuration of the bony elements and epidermal structures that form the wings1,2. Whereas the early fossil records of pterosaurs and bats are sparse, mounting evidence (primarily from China) of feathered non-avian dinosaurs and stemward avians that derive primarily from the Middle–Upper Jurassic and Lower Cretaceous periods has enabled the slow piecing together of the origins of avian flight3,4. These fossils demonstrate that, close to the origin of flight, dinosaurs closely related to birds were experimenting with a diversity of wing structures3,5. One of the most surprising of these is that of the scansoriopterygid (Theropoda, Maniraptora) Yi qi, which has membranous wings—a flight apparatus that was previously unknown among theropods but that is used by both the pterosaur and bat lineages6. This observation was not universally accepted7. Here we describe a newly identified scansoriopterygid—which we name Ambopteryx longibrachium, gen. et sp. nov.—from the Upper Jurassic period. This specimen provides support for the widespread existence of membranous wings and the styliform element in the Scansoriopterygidae, as well as evidence for the diet of this enigmatic theropod clade. Our analyses show that marked changes in wing architecture evolved near the split between the Scansoriopterygidae and the avian lineage, as the two clades travelled along very different paths to becoming volant. The membranous wings supported by elongate forelimbs that are present in scansoriopterygids probably represent a short-lived experimentation with volant behaviour, and feathered wings were ultimately favoured during the later evolution of Paraves.
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All data—including the measurements, source data for morphometric analysis and phylogenetic data matrix—that support the findings of this research are included as Supplementary Information. The specimen (IVPP V24192) described in this study is archived and available on request from the IVPP. A Life Science Identifier for the newly described species has been registered at ZooBank (http://zoobank.org/): urn:lsid:zoobank.org:act:0A2DE2F0-CE78-4149-B0BD-A0DE91FC1328. Any other relevant data are available from the corresponding author upon reasonable request.
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
We thank S.-X. Jiang, D.-Y. Huang, Y.-H. Pan and Z.-Q. Yu for discussion, Q.-R. Meng for help in the field, T. Zhao for taking scanning electron microscopy photographs, D.-H. Li for specimen preparation and W. Gao for photographing. This research was supported by the National Natural Science Foundation of China (41688103; 41722202), Youth Innovation Promotion Association CAS (2016073) and the State Key Laboratory of Lithospheric Evolution (Z201604).
Nature thanks Thomas Richard Holtz, Peter Makovicky and Kevin Padian for their contribution to the peer review of this work.