Book excerpt: Dinosaurs are usually pictured in warm, tropical environments, but fossils found at the poles are filling in the gap of knowledge about how and where these creatures lived. Evidence from bones and teeth to trackways and skin impressions raises important questions: How did dinosaurs cope with three months of total darkness in winter? What plants grew in the polar regions? How cold was it? What are the implications for today, as glaciers retreat, ice shelves melt, and permafrost thaws? The polar regions are a unique "library" of the past, and Caroline Arnold introduces readers to the gigantic prehistoric creatures that inhabited them.