[calex59]

That’s because there were no “harsh polar Regions” back then.

[CanadianPete]

"That’s because there were no “harsh polar Regions” back then." Actually, as I remember it they said that the environment up to the arctic circle was about like it is in Anchorage today. They actually show that from the fossils. They then talk about if the dinosaurs migrated for winter or wintered there. They show that it wasn't possible for them to migrate so they wintered there. Therefore they must be warmblooded, I think.