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Jeholornis: Two-Tailed Wonder

News today of a more proximal tail fan in Jeholornis:

Jingmai O’Connor, Xiaoli Wang, Corwin Sullivan, Xiaoting Zheng, Pablo Tubaro, 
Xiaomei Zhang, and Zhonghe Zhou
Unique caudal plumage of Jeholornis and complex tail evolution in early birds 
PNAS 2013 ; published ahead of print October 7, 2013, 

We describe the presence of essentially two functional tails in the Early 
Cretaceous Jeholornis (the second most primitive bird)—one like that of some 
modern birds with a fan-shaped tract of feathers over the proximal tail 
vertebrae and another distal frond like that of feathered dinosaurs such as 
Caudipteryx and Microraptor. We suggest that the unique “two-tail” plumage in 
Jeholornis probably evolved as the result of complex interactions between 
natural and sexual selective pressures and served both aerodynamic (flight and 
balance, etc.) and ornamental functions (communication/display, etc.). Our 
aerodynamic analysis also provides a plausible functional explanation for the 
elongation of the boney tail in Jeholornis relative to Archaeopteryx.