NOVA: Arctic Dinosaurs

"Warm-Blooded Creatures of the Cretaceous?"

Dinosaurs are generally considered tropical animals. So what are their fossils doing north of the arctic circle? Paleontologists battle the fierce climate to find out if the arctic was warmer then than it is now, or the arctic was farther from the North Pole, or the dinosaurs were migratory animals, or if they were warm-blooded.