Cellular preservation of musculoskeletal specializations in the Cretaceous bird Confuciusornis.
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.
School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China.|State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 210008, China.
Baoyu
B
Jiang
School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China.
Tao
T
Zhao
Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, The Royal Veterinary College, University of London, Hatfield, Hertfordshire AL9 7TA, UK.
Sophie
S
Regnault
School of Earth and Environmental Sciences, University of Manchester, Manchester M13 9PL, UK.
Nicholas P
NP
Edwards
School of Earth Sciences, University of Bristol, Bristol BS8 1TH, UK.
Simon C
SC
Kohn
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.
Zhiheng
Z
Li
School of Earth and Environmental Sciences, University of Manchester, Manchester M13 9PL, UK.
Roy A
RA
Wogelius
School of Earth Sciences, University of Bristol, Bristol BS8 1TH, UK.
Michael J
MJ
Benton
Structure and Motion Laboratory, Department of Comparative Biomedical Sciences, The Royal Veterinary College, University of London, Hatfield, Hertfordshire AL9 7TA, UK.
John R
0000-0002-6767-7038
JR
Hutchinson
D000818:Animals; D001717:Birds / Q000033:anatomy & histology*; D025061:Dinosaurs / Q000033:anatomy & histology*; D005121:Extremities / Q000033:anatomy & histology; D005580:Fossils; D006614:Hindlimb / Q000033:anatomy & histology; D009141:Musculoskeletal System / Q000033:anatomy & histology*; D013997:Time Factors