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Here is paper you might find interesting as it regards a possible geographic origin of early birds and mammals: Sven Kurbel (2013) Hypothesis of homeothermy evolution on isolated South China Craton that moved from equator to cold north latitudes 250 to 200 Myr ago. Journal of Theoretical Biology (advance online publication) doi: http://dx.doi.org/10.1016/j.jtbi.2013.09.018 http://www.sciencedirect.com/science/article/pii/S0022519313004463 While the climate of southern China during the Early Jurassic provides a window into the geographic origins of homeothermic animals (mammals, birds), the problem with the validity of the hypothesis is that all Early Jurassic theropod dinosaurs found in South China are non-tetanuran (although theropod footprints in Inner Mongolia suggest that there may be Early Jurassic theropod body fossils waiting to be found in Inner Mongolia) and that the oldest paravians (Pedopenna, Xiaotingia, Eosinopteryx, Aurornis) are of Middle-Late Jurassic age. However, it's not hard to imagine a Middle Jurassic paravian occurring in South China because the Oxfordian-age alvarezsaur Haplocheirus is closer to paravians, therizinosaurs, and oviraptorosaurs than to any other coelurosaur group. Only time will they if the hypothesis of an Asian origin for Avialae based on climatic conditions in southern China during the Early Jurassic is valid.