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Zhongjianornis: another goshdarn basal avialian from the Jiufotang


Zhou, Z., F. Zhang & Z. Li. 2009. A new Lower Cretaceous bird from China and
tooth reduction in early avian evolution. Proc. R. Soc. B published online
before print July 8, 2009, doi:10.1098/rspb.2009.0885


A new avian genus and species, Zhongjianornis yangi gen. et sp. nov., is
reported from the Lower Cretaceous lacustrine deposits of the Jiufotang
Formation in Liaoning, northeast China. The new taxon is characterized by
possessing the following combination of features: upper and lower jaws
toothless, snout pointed, humerus with large and robust deltopectoral crest,
second phalanx of the major manual digit longer than the first phalanx,
unguals of the alular and major digits of similar length and significantly
shorter than the corresponding penultimate phalanges, tibiotarsus slender
and more than twice the length of the tarsometatarsus, and metatarsal IV
longer than the other metatarsals. Phylogenetic analysis indicates that
Zhongjianornis is phylogenetically basal to Confuciusornis and the dominant
Mesozoic avian groups, Enantiornithes and Ornithurae, and therefore provides
significant new information regarding the diversification of birds in the
Early Cretaceous. It also represents the most basal bird that completely
lacks teeth, suggesting that tooth loss was more common than expected in
early avian evolution and that the avian beak appeared independently in
several avian lineages, most probably as a response to selective pressure
for weight reduction. Finally, the presence of a significantly enlarged
humeral deltopectoral crest suggests that Zhongjianornis shares with other
basal birds such as Jeholornis, Sapeornis and Confuciusornis a distinctive
mode of adaptation for flight contrasting with that seen in more advanced
birds, which instead possess an elongated sternum and a prominent keel. 

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216                        
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Fax: 301-314-9661               

Faculty Director, Earth, Life & Time Program, College Park Scholars
Faculty Director, Science & Global Change Program, College Park Scholars
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA