Figure 21: Dinosaurs migrating in herds.

Ectotherms cannot live in the extremely cold areas near the poles because not enough solar energy reaches the surface of the earth to warm up their blood. The current geographic distribution of dinosaur fossils encompasses Cretaceous localities as far north as Alaska and as far south as Antarctica. The Cretaceous world was not as cold at the poles as they are today, and because of continental drift these locations were not as poleward as they are today. Despite these factors the poles still would have been cold enough to prevent ectotherms from living there. It is possible though that these animals may have migrated northward to these areas when it was the warmer and brighter portion of the year. Since migration is possible it is hard to argue that fossils found in these locations supports the argument of endothermy.