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Basal tyrannosauroids from China and evidence for protofeathers in tyrannosauroids

Abstract

Tyrannosauroids are one of the last and the most successful large-bodied predatory dinosaur groups1,2,3,4,5, but their early history remains poorly understood. Here we report a new basal tyrannosauroid from the Early Cretaceous Yixian Formation of western Liaoning, China, which is small and gracile and has relatively long arms with three-fingered hands. The new taxon is the earliest known unquestionable tyrannosauroid found so far6,7,8,9. It shows a mosaic of characters, including a derived cranial structure resembling that of derived tyrannosauroids1,2,3,4,5 and a primitive postcranial skeleton similar to basal coelurosaurians. One of the specimens also preserves a filamentous integumentary covering similar to that of other coelurosaurian theropods from western Liaoning. This provides the first direct fossil evidence that tyrannosauroids had protofeathers.

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Acknowledgements

We thank T. Holtz, O. Rauhut and X.-C. Wu for critical comments on the manuscript; Z. H. Zhou, Z. L. Tang, Y. Q. Wang, Y. Li, H. J. Wang, Y. L. Huo, H. Q. Shou, X.Z. Liu, Q. Cao, W. Chen, J. C. Lu and C. Li for their contribution in the field; H. J. Wang, J. M. Yang, G. H. Cui and X. Q. Ding for preparing the specimens; and R. S. Li, J. L. Huang and M. W. Yang for illustrations. The study was supported by the Special Funds for Major State Basic Research Projects of China, the National Natural Science Foundation of China, the National Geographic Society, the Chinese Academy of Sciences, the National Science Foundation of the USA and the American Museum of Natural History.

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Correspondence to Xing Xu or Mark A. Norell.

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The authors declare that they have no competing financial interests.

Supplementary information

Supplementary Information

Measurements of selected elements in the available specimens; Ontogenetic assessments for the available specimens; Cladistic analysis for evaluating the phylogenetic position of Dilong; Tyrannosauroid synapomorphies (DOC 110 kb)

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Further reading

Figure 1: Dilong paradoxus.
Figure 2: IVPP V11579.
Figure 3: Integumentary structures of IVPP V11579.

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