Reproduction in living birds differs markedly from that of other modern vertebrates in the rate of egg production, egg size and shape, microscopic structure of the eggshell, nest form, method of incubation, and the manner and prevalence of parental care. The disparity between birds and other living vertebrates raises questions as to how and when this unique reproductive style evolved. Did it originate before or after the achievement of flight? Were the carnivorous theropod dinosaurs from which birds evolved reproductively more similar to their dinosaur relatives or to modern birds? How important were the reproductive and life history strategies of Mesozoic dinosaurs to their success? The proposed research addresses these questions by documenting the evolution of reproductive traits through the Mesozoic from dinosaurs to birds. The investigation consists of four phases: 1) study of modern bird and crocodile nesting localities for attributes that would help interpret dinosaur sites, 2) investigation of Cretaceous theropod dinosaur nesting sites, 3) construction of an evolutionary history of reproductive traits based on field, laboratory, and museum study and 4) comparison of the life history strategies among theropod dinosaurs, other dinosaurs, and living egg-laying vertebrates. Strengths of this study include an interdisciplinary team with expertise in taphonomy (the study of fossil preservation), eggshell structure, and the nesting behavior of modern birds, as well as an unsurpassed suite of modern and fossil samples. Modern nesting localities represent both crocodilians and birds that exhibit a wide array of reproductive behaviors. The Mesozoic dinosaur sample includes four egg types from the Cretaceous of Montana and Idaho; these four egg types represent the only in place theropod dinosaur eggs from North America. The study of modern nesting horizons provides the framework for interpreting fossil nesting localities. Data generated from the studies of modern crocodilians and birds will allow recognition of patterns and processes affecting fossil preservation. The combination of extensive fieldwork, laboratory analysis of eggs, and the exceptional fossil sample will provide new insights on egg preservation and the reproductive behavior of theropod dinosaurs. Identification of new egg characters and resolution of controversial issues regarding theropod reproductive behavior will strengthen our evolutionary understanding. Documentation of the evolutionary history of reproduction in birds and their theropod dinosaurs ancestors, will provide insight into the origination of birds. Comparison of modern and extinct life history strategies among crocodilians, dinosaurs, and birds will increase current understanding of dinosaur ecology, test life history theory on a macroevolutionary scale, and permit evaluation of factors potentially contributing to the overall success of dinosaurs throughout the Mesozoic. Educational goals include incorporation of research observation and interpretation into university courses and professional development for rural Montana science teachers through workshops and fieldwork participation. Additionally, the project will support research opportunities for two masters and eight undergraduate students. Finally, Varricchio serves as host committee chair for the 4th International Symposium on Dinosaur Eggs and Babies to be held at Montana State University in the summer of 2009. This meeting provides an excellent opportunity for dissemination of the research results, while facilitating greater exchange of ideas between biologists and paleontologists regarding the evolution of bird and dinosaur reproduction.
