Four-Winged Birds?

` ... or is it just Microraptor, which was a tiny dromaeosaur (like Velociraptor), not a bird. I've been wondering how the debate over the different stages in flight evolution in birds. It's hard to tell, really, though I do have small glimpses occationally...

Origin of flight: Could 'four-winged' dinosaurs fly?

Kevin Padian¹ and Kenneth P. Dial²

Arising from: X. Xu et al. Nature 421, 335–340 (2003); F. Zhang & Z. Zhou Nature 431, 925 (2004); X. Xu et al. reply; F. Zhang et al. reply

Our understanding of the origin of birds, feathers and flight has been greatly advanced by new discoveries of feathered non-avian dinosaurs, but functional analyses have not kept pace with taxonomic descriptions. Zhang and Zhou describe feathers on the tibiotarsus of a new basal enantiornithine bird from the Early Cretaceous of China¹. They infer, as did Xu and colleagues from similar feathers on the small non-avian theropod Microraptor found in similar deposits², that these leg feathers had aerodynamic properties and so might have been used in some kind of flight.

1. Museum of Paleontology, University of California, Berkeley, California 94720, USA
2. Division of Biological Sciences, University of Montana, Missoula, Montana 59812, USA

Origin of flight: Could 'four-winged' dinosaurs fly? (Reply)

Xing Xu^1,2, Zhonghe Zhou¹, Xiaolin Wang¹, Xuewen Kuang³, Fucheng Zhang¹ and Xiangke Du⁴

We agree that a strict biomechanical analysis is needed to reconstruct Microraptor's locomotory mode, but we disagree with several of Padian and Dial's arguments¹. In addition to the six Microraptor specimens we described², other similarly preserved specimens³ have been discovered that also had long, asymmetrical pennaceous feathers attached to the hindlimbs². These feathers show features that are functionally correlated with flight⁴. A large, feathery surface on the legs would increase, rather than decrease¹, drag during running, as evidenced by the reduced or lost filamentous integumentary structures on the lower legs of cursorial birds and mammals.

1. Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China
2. Present address: American Museum of Natural History, New York, New York 10024, USA
3. Tianjin Museum of Natural History, Tianjin 300074, China
4. Radiological Department, People's Hospital, Beijing University, Beijing 100044, China

Origin of flight: Could 'four-winged' dinosaurs fly? (Reply)

Zhonghe Zhou¹ and Fucheng Zhang¹

Padian and Dial¹ challenge our view that the evolution of flight involved a four-winged stage. This disagreement stems from our different views on the origin of bird flight and from the methodology we use to analyse functional morphology in the non-avian theropod Microraptor² and in an enantiornithine bird³ from the Early Cretaceous period in China.

1. Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
   

` Neato, huh? Eh. Well, I'm off to take a nap and then hopefully eat something. I'm very hungry and sleep-deprived and there will be no food in the house until Phil and Jason come back from their walk to QFC.