Dinosaurs at the poles

How did dinosaurs, traditionally thought of as tropical or subtropical creatures, survive near the poles? After all, it was chilly up there (and down there) even in the Mesozoic. The annual mean temperature at the poles was about 41 F or 5 C - balmy compared to modern climates, but too cold for for what we used to think were basically cold-blooded animals.
One idea was that dinos living near the poles made long seasonal migrations, as many modern birds do. Fossil evidence, though, as well as a comparison to modern polar land animals, indicates that many species did not migrate, or at least did not migrate as far as we thought. As Phil Bell of the University of Alberta explains, "Many types of dinosaurs were surviving in polar latitudes at the time, and getting along quite fine. They were not physically able to remove themselves from the environment for a variety of reasons and had to adapt to the cold, dark winters just as the rest of us mammals do today." Bell and co-author Eric Snively have shown us all, once again, that we have a lot to learn about our favorite fossil creatures.