Phylogenetic Relationships of Birds to Other Dinosaurs

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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.