Phylogenetic Relationships of Birds to Other Dinosaurs

9407999美国自然历史博物馆和蒙古科学院联合考察队在蒙古晚白垩世沉积物中进行了四个野外季节的化石采集，收集了大量兽脚类恐龙骨架，其中包括被认为是鸟类最近亲属的分类群。这些藏品和美国博物馆的大量恐龙藏品是一项评估鸟类与其他兽脚类恐龙关系的拟议分析的重点。重点将放在开发基于CAT扫描图像的头骨中的新字符系统。在过去的十年里，支持这一假设的证据迅速增加，即鸟类与兽脚类恐龙的亲缘关系最近，而且确实是兽脚类恐龙。然而，鸟类与兽脚类恐龙之间的确切关系存在争议，最原始的鸟类之间的关系也是如此。与这些问题相关的大量证据是存在的，但只有通过CAT扫描和人工准备化石，然后与世界各地博物馆广泛分布的其他标本进行比较，才能获得这些证据。这项研究阐明的解剖学细节及其产生的历史假说将为鸟类起源和鸟类飞行起源的研究提供坚实的基础。

9407999 Norell Four field seasons of fossil collecting in Late Cretaceous deposits of Mongolia by joint expeditions of the American Museum of Natural History and the Mongolian Academy of Sciences amassed a large collection of theropod dinosaur skeletons, including taxa considered to be among the closest relatives of birds. This collection and the vast dinosaur collections of the American Museum are the focus of a proposed analysis assessing the relationships of birds to other theropod dinosaurs. Emphasis will be placed on developing new character systems in the skull based on CAT scan images. Evidence for the hypothesis that birds are most closely related to theropod dinosaurs, and indeed are theropod dinosaurs, has rapidly mounted during the last decade. However, the precise relationships of birds to theropod dinosaurs is controversial, as are the relationships among the most primitive birds. A great deal of evidence relevant to these questions exists but can only be made available by CAT scans and manual preparation of fossils followed by comparison with other specimens widely scattered in museums around the world. The anatomical details elucidated by this study and the historical hypotheses it generates will provide a solid foundation for studies of bird origins and the origin of avian flight.