The dinosaurs in the polar reason isn't because it was warmer, it's because the Strait of Magellan were closed.

One of the reasons we are in an ice age right now (which refers to a period where you have periodicly advancing and retreating glaciers) is because you have a continent on the pole and a clear sea lane around it, before the Strait of Magellan opened you have a current that circulated between the poles and equater evening out the temperatures allowing for ice free poles.