The phylogenetic position of Ambiortus: Comparison with other Mesozoic birds from Asia
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- O’Connor, J.K. & Zelenkov, N.V. Paleontol. J. (2013) 47: 1270. doi:10.1134/S0031030113110063
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Since the last description of the ornithurine bird Ambiortus dementjevi from Mongolia, a wealth of Early Cretaceous birds have been discovered in China. Here we provide a detailed comparison of the anatomy of Ambiortus relative to other known Early Cretaceous ornithuromorphs from the Chinese Jehol Group and Xiagou Formation. We include new information on Ambiortus from a previously undescribed slab preserving part of the sternum. Ambiortus is superficially similar to Gansus yumenensis from the Aptian Xiagou Formation but shares more morphological features with Yixianornis grabaui (Ornithuromorpha: Songlingornithidae) from the Jiufotang Formation of the Jehol Group. In general, the mosaic pattern of character distribution among early ornithuromorph taxa does not reveal obvious relationships between taxa. Ambiortus was placed in a large phylogenetic analysis of Mesozoic birds, which confirms morphological observations and places Ambiortus in a polytomy with Yixianornis and Gansus.