Abstract
The recently reported Jeholornis represents the only known bird with a complete long skeletal tail except for Archaeopteryx. Two newly discovered specimens referable to Jeholornis provide some important new information about its anatomy. The tail of Jeholornis is much longer than that of Archaeopteryx and comprises a maximum of 27 caudal vertebrae compared with only 23 in Archaeopteryx. More interestingly, the tail feathers are shaped more like those of dromaeosaurs than those of Archaeopteryx. We conclude that the common ancestor of birds must have a more primitive tail than that in Archaeopteryx, confirming the side branch position of Archaeopteryx in the early avian evolution. The synsacrum is composed of six sacrals, representing a transitional stage between Archaeopteryx and more advanced birds. The scapula of Jeholornis has a dorso-laterally exposed glenoid facet, and the coracoid has a supracoracoid foramen. The presence of a pair of fenestrae in the sternum of Jeholornis has further implications for the air-sac system in early birds.
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Acknowledgements
We thank L.D. Martin, P. Currie and L. M. Chiappe for discussions, and X. Wang for help in the field. Y. Li prepared the specimens. This work was supported by the National Natural Science Foundation of China, Special Funds for Major State Basic Research Projects of China (G2000077700) and the Chinese Academy of Sciences.
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Zhou, Z., Zhang, F. Jeholornis compared to Archaeopteryx, with a new understanding of the earliest avian evolution. Naturwissenschaften 90, 220–225 (2003). https://doi.org/10.1007/s00114-003-0416-5
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DOI: https://doi.org/10.1007/s00114-003-0416-5