Zhonghe Zhou* and Fucheng Zhang Zhiheng Li
+ Author Affiliations
Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 142 Xi-Wai-Da-Jie, PO Box 643, Beijing 100044, People's Republic of China
*Author for correspondence (zhonghe@yeah.net).
Source/Fonte
Holotype of Zhongjianornis yangi gen. et sp. nov. (Image: Zhonghe Zhou and Fucheng Zhang Zhiheng Li)
Abstract
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.
Lower Cretaceous bird evolution beak China
Footnotes
One contribution to a Special Issue ‘Recent advances in Chinese palaeontology’.
Received May 23, 2009.
Accepted June 19, 2009.
© 2009 The Royal Society
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LÓGICA EVOLUTIVA 101:
Uma espécie tinha dentes porque lhe era vantajoso evolutivamente, e depois no transformismo em uma outra espécie, esses mesmos dentes outrora vantajosos, já não são mais.
Onde foi mesmo que eu me perdi no curso de Lógica Evolutiva 101???
