Letter

Synchrotron scanning reveals amphibious ecomorphology in a new clade of bird-like dinosaurs

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Abstract

Maniraptora includes birds and their closest relatives among theropod dinosaurs1,2,3,4,5. During the Cretaceous period, several maniraptoran lineages diverged from the ancestral coelurosaurian bauplan and evolved novel ecomorphologies, including active flight2, gigantism3, cursoriality4 and herbivory5. Propagation X-ray phase-contrast synchrotron microtomography of a well-preserved maniraptoran from Mongolia, still partially embedded in the rock matrix, revealed a mosaic of features, most of them absent among non-avian maniraptorans but shared by reptilian and avian groups with aquatic or semiaquatic ecologies6,7,8,9,10,11,12,13,14. This new theropod, Halszkaraptor escuilliei gen. et sp. nov., is related to other enigmatic Late Cretaceous maniraptorans from Mongolia15,16 in a novel clade at the root of Dromaeosauridae17. This lineage adds an amphibious ecomorphology to those evolved by maniraptorans: it acquired a predatory mode that relied mainly on neck hyperelongation for food procurement, it coupled the obligatory bipedalism of theropods with forelimb proportions that may support a swimming function, and it developed postural adaptations convergent with short-tailed birds.

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Acknowledgements

We thank the European Synchrotron Radiation Facility for granting us beam time at ID19 and BM05 beamlines; Y. Pommery for his work on teeth segmentation; T. Hubin for photographs; A. Halamski and D. Madzia for information on Hulsanpes holotype; and M. Auditore for the skeletal reconstructions. U. Lefèvre and L. Van Bossuyt took conventional X-ray pictures at the Veterinary School of Liège University. Silhouettes in Fig. 4a were provided by D. Bonadonna and L. Panzarin and are used with their permission. The program TNT was made available by the sponsorship of the Willi Hennig Society.

Author information

Affiliations

  1. Geological and Palaeontological Museum ‘Giovanni Capellini’, I-40126 Bologna, Italy

    • Andrea Cau
  2. European Synchrotron Radiation Facility, F-38043 Grenoble, France

    • Vincent Beyrand
    • , Dennis F. A. E. Voeten
    • , Vincent Fernandez
    •  & Paul Tafforeau
  3. Department of Zoology and Laboratory of Ornithology, Palacký University, CS-40220 Olomouc, Czech Republic

    • Vincent Beyrand
    •  & Dennis F. A. E. Voeten
  4. Earth System Science – AMGC Vrije Universiteit Brussel, B-1050 Brussels, Belgium

    • Koen Stein
  5. Palaeontological Center, Mongolian Academy of Sciences, Ulaanbaatar 201-351, Mongolia

    • Rinchen Barsbold
  6. Institute of Palaeontology and Geology, Mongolian Academy of Sciences, Ulaanbaatar 210-351, Mongolia

    • Khishigjav Tsogtbaatar
  7. Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada

    • Philip J. Currie
  8. Directorate Earth & History of Life, Royal Belgian Institute of Natural Sciences, B-1000 Brussels, Belgium

    • Pascal Godefroit

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Contributions

A.C. and P.G. designed the project. P.G. supervised the preparation of the specimen. P.T., V.B., D.F.A.E.V. and V.F. performed synchrotron scanning, data processing and segmentation, and created the 2D and 3D renderings. K.S. conducted the histological analysis. R.B., K.T. and P.J.C. provided information on Mongolian theropods and geological setting. A.C. conducted the phylogenetic analyses. A.C. wrote the manuscript with input from all other authors.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Andrea Cau.

Reviewer Information Nature thanks T. Holtz Jr and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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