Brain evolution in archosaurs: new implications for scaling, function, and the evolution of the modern conditions in birds and crocodilians

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Brain evolution in archosaurs: new implications for scaling, function, and the evolution ofthe modern conditions in birds and crocodiliansLawrence M. WitmerOhio UniversityThe brain is justifiably regarded as the single most important organ, and thus its neurobiology and evolution have long been a central interest of organismal biology. This project studies brain evolution in Archosauria, the group including birds and crocodilians today and dinosaurs, pterosaurs, and basal forms during the Mesozoic, with the aims of shedding light on the evolution of the modern condition and using new methods to make the most accurate estimates, to date, of relative brain size and shape in extinct archosaurs. Because fossils usually preserve only hard parts, a major objective is to make assessments of the brain cavity of extinct archosaurs by reconstructing component soft tissues, which will then provide a basis for functional interpretation. Hypotheses will be tested in the context of the extant phylogenetic bracket (EPB) approach whereby the modern relatives (birds, crocodilians, lizards) of the fossil group (dinosaurs) provide information on the relationship between soft tissues and the signatures they leave on the bones. Pertinent soft tissues (the brain, its coverings, nerves, blood vessels) will be studied in the modern animals using a range of methods, including a novel imaging technique developed in the PI's lab, to discover their bony correlates. Fossil archosaurs will then be surveyed for these signatures. CT scanning of literally dozens of pivotal fossil specimens will be a critical tool in that it will not only provide data on features embedded within the skull but also will yield 3D digital datasets from which highly accurate measurements can be made automatically. A new method to estimate the size and shape of the brain in dinosaurs (GABRA: gross anatomical brain region approximation) will be refined, allowing new scaling studies of relative brain size using the latest statistical techniques. This information will be mapped onto a genealogical tree of archosaurs to assess the adaptive contexts of major transitions in brain conformation by making correlations with broad behavioral and physiological categories. Numerous undergraduate and graduate students will receive technical and analytical training. The project is highly collaborative, involving many paleontologists and experimentalists worldwide. The extensive radiological imaging will require development of refined imaging protocols, standardized analyses, specialized workstations, and bioinformatics innovations to deal with the voluminous multi-format digital data. Internet-based means of not only disseminating the data but also manipulating the data will be essential, and will take place in connection with existing bioinformatics hubs. Given the continual K-12 interest in all things dinosaurian, the attention this project will attract will provide new opportunities to use dinosaurs as tools to teach about science in general, with expected venues being media outlets, school or other public appearances, and the internet.