Cellular preservation of musculoskeletal specializations in the Cretaceous bird Confuciusornis
Baoyu Jiang, Tao Zhao, Sophie Regnault, Nicholas P. Edwards, Simon C. Kohn, Zhiheng Li, Roy A. Wogelius, Michael J. Benton & John R. Hutchinson
Nature Communications 8, Article number: 14779 (2017)
Received: 14 January 2016 Accepted: 02 February 2017 Published online: 22 March 2017
The hindlimb of theropod dinosaurs changed appreciably in the lineage leading to extant birds, becoming more ‘crouched’ in association with changes to body shape and gait dynamics. This postural evolution included anatomical changes of the foot and ankle, altering the moment arms and control of the muscles that manipulated the tarsometatarsus and digits, but the timing of these changes is unknown. Here, we report cellular-level preservation of tendon- and cartilage-like tissues from the lower hindlimb of Early Cretaceous Confuciusornis. The digital flexor tendons passed through cartilages, cartilaginous cristae and ridges on the plantar side of the distal tibiotarsus and proximal tarsometatarsus, as in extant birds. In particular, fibrocartilaginous and cartilaginous structures on the plantar surface of the ankle joint of Confuciusornis may indicate a more crouched hindlimb posture. Recognition of these specialized soft tissues in Confuciusornis is enabled by our combination of imaging and chemical analyses applied to an exceptionally preserved fossil.
We thank Zhonghe Zhou, Jin Meng, Junfeng Ji, Xiancai Lu, Julia Clarke and Maria McNamara for discussions, and Yan Fang, Wuping Li, Tong He, H. Jones, M. Hethke, M. Hill, A. Davidson, Junying Ding and Huan Liu for laboratory assistance. This work was supported by the National Science Foundation of China (41672010, 41688103) and State Key Laboratory of Palaeobiology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences) (153104) to B.J., as well as a Royal Society Leverhulme Trust senior research fellowship, Leverhulme Trust research Grant Number RPG-2013-108 and Natural Environment Research Council Grant Number NE/K004751/1 to J.R.H. We thank the staff at the Diamond Light Source, beamline I18 (beam allocation SP9488). We also thank Nick Lockyer for discussions about the ToF–SIMS data.
School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
Baoyu Jiang & Tao Zhao
State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 210008, China
Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, The Royal Veterinary College, University of London, Hatfield, Hertfordshire AL9 7TA, UK
Sophie Regnault & John R. Hutchinson
School of Earth and Environmental Sciences, University of Manchester, Manchester M13 9PL, UK
Nicholas P. Edwards & Roy A. Wogelius
School of Earth Sciences, University of Bristol, Bristol BS8 1TH, UK
Simon C. Kohn & Michael J. Benton
Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
B.J. and J.R.H. designed the research, B.J. and T.Z. studied the histology (including SEM) of the fossils, S.R. and J.R.H. made the histological comparisons between fossils and extant birds, N.P.E. and R.A.W. carried out the synchrotron rapid-scanning X-ray fluorescence and X-ray absorption near-edge structure spectroscopies, B.J. did the ToF–SIMS analysis, M.J.B. and S.C.K. did the FTIR analysis, Z.L. and S.R. did the microCT reconstructions, and B.J., R.A.W., M.J.B. and J.R.H. wrote the paper; all authors approved the final draft of the paper.
The authors declare no competing financial interests.
Correspondence to Baoyu Jiang or John R. Hutchinson.
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