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A bizarre Jurassic maniraptoran theropod with preserved evidence of membranous wings



The wings of birds and their closest theropod relatives share a uniform fundamental architecture, with pinnate flight feathers as the key component1,2,3. Here we report a new scansoriopterygid theropod, Yi qi gen. et sp. nov., based on a new specimen from the Middle–Upper Jurassic period Tiaojishan Formation of Hebei Province, China4. Yi is nested phylogenetically among winged theropods but has large stiff filamentous feathers of an unusual type on both the forelimb and hindlimb. However, the filamentous feathers of Yi resemble pinnate feathers in bearing morphologically diverse melanosomes5. Most surprisingly, Yi has a long rod-like bone extending from each wrist, and patches of membranous tissue preserved between the rod-like bones and the manual digits. Analogous features are unknown in any dinosaur but occur in various flying and gliding tetrapods6,7,8,9,10, suggesting the intriguing possibility that Yi had membranous aerodynamic surfaces totally different from the archetypal feathered wings of birds and their closest relatives. Documentation of the unique forelimbs of Yi greatly increases the morphological disparity known to exist among dinosaurs, and highlights the extraordinary breadth and richness of the evolutionary experimentation that took place close to the origin of birds.

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Figure 1: Yi qi holotype (STM 31‐2).
Figure 2: Soft tissues preserved in Yi qi holotype (STM 31‐2).
Figure 3: Simplified coelurosaurian phylogeny showing the recovered position of Yi.


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We thank Z. Zhou, R. Dudley, J. Clarke and T. Stidham for discussion, X. Ding for specimen preparation, Y. Liu and Y. Han for providing illustrations, Z. Zhang for assistance with the EDS analysis, and Y. Hou for CT scanning the specimen. This research was funded by the National Natural Science Foundation of China (41372014, 41472023, 41120124002 and 41125008) and Major Basic Research Projects of the Ministry of Science and Technology, China (2012CB821900).

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Authors and Affiliations



X.X., X. Zheng and C.S. designed the project, X.X., X. Zheng, C.S., X.W., Y.W., L.X., X. Zhang, J.K.O’C., F.Z. and Y.P. performed the research, and X.X. and C.S. wrote the manuscript.

Corresponding authors

Correspondence to Xing Xu or Xiaoting Zheng.

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Competing interests

The authors declare no competing financial interests.

Additional information

Data have been deposited in ZooBank under Life Science Identifier (LSID) The raw CT data have been deposited in the Dryad Digital Repository (

Extended data figures and tables

Extended Data Figure 1 Fossil‐bearing beds of the Middle–Upper Jurassic Tiaojishan Formation in Qinglong County, Hebei.

The Mutoudeng Locality (top) and Gangou Locality (bottom) are geographically close to each other (approximately 20 km apart) and very similar in their sedimentology and fossil content. The bottom image shows an excavation we organized at the Gangou Locality.

Extended Data Figure 2 Photograph of the slab and counter slab of STM 31‐2.

Extended Data Figure 3 Close‐ups of the three counter slab fragments and corresponding slab regions of STM 31‐2.

Top row: isolated piece from counter slab preserving cranial region (left), and corresponding region of slab (right); middle row: isolated piece from counter slab preserving forelimb region (left), and corresponding region of slab (right); bottom row: isolated piece from counter slab preserving hindlimb region (left), and corresponding region of slab (right).

Extended Data Figure 4 Volumetric model generated from superimposed CT slices.

Because there is little density contrast between the fossil and the matrix, the outline of the fossil is somewhat vague.

Extended Data Figure 5 Photographs of preserved integumentary features of STM 31‐2.

acc, Feathers over the neck (a), along the humerus (b) and along the humerus and ulna (c); d, isolated basally converging feathers; e, sheet‐like soft tissue and feathers associated with the right forelimb and feathers along the right hindlimb; f, g, close‐ups of sheet‐like soft tissue associated with the right forelimb (f) and distal phalanges of manual digit IV (g).

Extended Data Figure 6 Elemental compositions of the styliform element and comparison samples based on EDS analyses.

EDS spectra derived from: a, right manual phalanx II‐1; b, right styliform element; c, feathers associated with right tibia; and d, sedimentary matrix.

Extended Data Figure 7 Aerodynamic apparatuses in Yi and other tetrapods.

acc, Wing of Yi, Bat Model (a), Maniraptoran Model (b), and Frog Model (c); d, bat wing; e, pigeon wing; f, pterosaur wing; g, giant Japanese flying squirrel wing. Yellow colour indicates styliform element in a, b, c, d, f, and g.

Extended Data Figure 8 Scanning electron microscopy sample locations.

Numbered circles indicate the locations of samples from the slab and counter slab. 1, distal part of cranial feathers; 2, middle part of tibial feathers; 3, distal part of humeral feathers; 4, distal part of ulnar feathers; 5, proximal part of cranial feathers; 6, proximal part of neck feathers; 7, distal part of humeral feathers; 8, distal part of humeral feathers; 9 and 10, membranous soft tissue near digit II; 11, membranous soft tissue near digit IV; 12, middle part of tibial feathers.

Extended Data Figure 9 Scanning electron microscopy images of melanosomes and melanosome impressions preserved in Yi qi holotype (STM 31‐2).

acm, Note the high morphological diversity of the preserved melanosomes in the feathers, which include: densely distributed, small round phaeomelanosomes and sparsely distributed, medium‐sized oval eumelanosomes in the feathers near the skull (a); medium‐sized elongate elliptical eumelanosomes in the feathers near the skull (b, c), neck (d, e), humerus (f, g), and ulna (h, i, j); and large oval and elliptical eumelanosomes in the feathers near the tibiotarsus (k, l). The subspherical phaeomelanosomes in the sheet‐like soft tissue (m) appear to be less densely distributed than the melanosomes in the feathers.

Extended Data Figure 10 Strict consensus of the 96 trees that resulted from analysis of a phylogenetic data matrix for coelurosaurs.

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Kerri Smith talks to palaeontologist Xing Xu and editor Henry Gee about an unexpected find in the dinosaur lineage leading to birds.

Supplementary information

Supplementary Information

This file contains Supplementary Text and Data, Supplementary Tables 1-2 and Supplementary References. (PDF 621 kb)

CT data for holotype of Yi qi

This data archive contains CT slice images in .dcm format for the slab containing the holotype specimen (STM, Shandong Tianyu Museum, 31-2) of Yi qi, a scansoriopterygid dinosaur from the Middle-Upper Jurassic of Mutoudeng, Hebei Province, China. The CT data reveal the 3D structure of the specimen, and of the slab itself. (AVI 25715 kb)

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Xu, X., Zheng, X., Sullivan, C. et al. A bizarre Jurassic maniraptoran theropod with preserved evidence of membranous wings. Nature 521, 70–73 (2015).

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