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A new troodontid dinosaur from China with avian-like sleeping posture


Discovering evidence of behaviour in fossilized vertebrates is rare. Even rarer is evidence of behaviour in non-avialan dinosaurs that directly relates to stereotypical behaviour seen in extant birds (avians) and not previously predicted in non-avialan dinosaurs1,2. Here we report the discovery of a new troodontid taxon from the Early Cretaceous Yixian Formation of western Liaoning, China. Numerous other three-dimensionally preserved vertebrate fossils have been recovered recently at this locality, including some specimens preserving behavioural information3. The new troodontid preserves several features that have been implicated in avialan origins. Notably, the specimen is preserved in the stereotypical sleeping or resting posture found in extant Aves4. Evidence of this behaviour outside of the crown group Aves further demonstrates that many bird features occurred early in dinosaurian evolution5,6.

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Figure 1: Holotype of Mei long (IVPP V12733).
Figure 2: Holotype of Mei long (IVPP V12733).


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We thank J. Meng, X.-J. Ni, Y.-M. Hu, J. Clarke and R. Prum for discussions, J.-M. Yang and H.-J. Wang for preparing the specimen, and M. Ellison for illustrations. We also thank Z.-H. Zhou and other members of the Liaoxi expedition team of the IVPP. This work was supported by grants from the National Natural Science Foundation of China, Special Funds for Major State Basic Research Projects of China, National Geographic Society, American Museum of Natural History, Chinese Academy of Sciences and National Science Foundation of USA.

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Correspondence to Xing Xu.

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Supplementary Data

Files include: (1) character list; (2) data matrix; (3) analysis results (including a figure); (4) lengths of elements in Mei long; (5) relative proportions of elements in some avian and non-avian theropods. (DOC 406 kb)

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Xu, X., Norell, M. A new troodontid dinosaur from China with avian-like sleeping posture. Nature 431, 838–841 (2004).

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