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 nameAmbopteryx 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.
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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).
Naturethanks Thomas Richard Holtz, Peter Makovicky and Kevin Padian for their contribution to the peer review of this work.
Extended data figures and tables
a, Counter slab.b, Skeletal reconstruction based on preserved bones.c, Skull.d, Gastroliths and the unidentified bony stomach content. Abbreviations as in Fig. 1, except for: fe, feather associated with the neck; lil, left ilium;; lti, left tibia; pd, pedal digits; and ub, unidentified bony element. The white box indicates the position from which the sample was taken for histological analysis. Scale bars, 10 mm (a,c,d), 20 mm (b).
a–d, Thin cross-section of the left humerus (a,b) and the unidentified bony stomach content (c,d). The arrowheads indicate the osteocyte lacunae. Scale bars, 100 μm (a–c), 200 μm (d).
a–d, Interpretative drawings of the neck and pectoral girdle (a), caudal vertebrae and pygostyle (b), left forelimb (c) and pelvis and left hindlimb (d). Abbreviations as in Figs. 1,2, except for: ca, caudal vertebrae; cm, calcaneum; de, deltopectoral crest of humerus; do, dorsal vertebrae; I–III, metacarpals I–III; ip, iliac peduncle of ilium; mtII–IV, metatarsals II–IV; p1–4, pedal digits I to IV; and st, styliform element. Scale bars, 10 mm (a–d).
a, Left forelimb ofAmbopteryx(IVPP V24192).b–d, Left forelimb (b), right humerus (c) and the right styliform element (d) ofYi(STM 31-2). The proximal margins of the humeri are marked in white dashed lines to show the differences between these two taxa. Abbreviations as in Figs. 1,2, except for: st, styliform element. Scale bars, 10 mm (a), 20 mm (b–d).
a–c, Line drawings of the hands ofAmbopteryx(a),Epidendrosaurus(b) andYi(c). Scale bars, 10 mm (a,b), 20 mm (c).
Extended Data Fig. 6 Scanning electron microscopy photographs of the soft tissues that are preserved inAmbopteryx.
a–d, Feather samples associated with the neck.e–f, Samples of membranous tissues taken from the area between the left femur and left manual digits. Arrows denote the positions of the samples. Scale bars, 2 μm.
Bremer and bootstrap values are labelled near the corresponding node in bold italic and upright non-bold font, respectively.
Extended Data Fig. 8 Compiled super-tree of the sampled Mesozoic coelurosaurians used in morphometric analyses.
Complete tree for the coelurosaurians used in generating the PPCA morphospaces shown in Fig. 3b, c.
This file contains Supplementary Text Sections 1–5; which include additional anatomical description, stomach contents and diet ofAmbopteryx longibrachium, Supplementary Tables 1, 2, 4 and 5, and the data used in the phylogenetic analysis.
This file contains appendicular limb bone measurements of Mesozoic coelurosaurians used in the phylogenetic principal components analysis.