The idea that dinosaurs lived at the poles is based on remarkable finds made in Australia. There are two clues that Australia was once within the Antarctic Circle. Firstly, we can can determine at what latitude rocks formed from the orientation of magnetic particles within them. Secondly, evidence that the climate was seasonally cold comes from both plant fossils and sedimentary structures which form when the ground freezes. A better picture The fossil sites in Australia are remarkable because several different animals have been found, giving us a fuller picture of the palaeoenvironment (life in the area at the time). At least some of the animals must have been year-round residents - Leaellynasaura were too small to have migrated hundreds of miles in and out every year. Leaellynasaura may have had a special adaptation for life in the polar regions. Their skulls seem to have had especially large eye sockets. Their large eyes may have allowed them to see better in the continuous low light levels of the polar winter. Hanging in there Some of the fossil vertebrates at these sites are very important because some very primitive animals that had become extinct elsewhere seem to have survived here. Labyrinthodont amphibians, like Koolasuchus, were previously thought to have died out over 100 million years earlier. In this environment it occupied a crocodilian niche, as the climate was too cold for crocodiles. The earliest known dinosaur found in polar palaeolaltitudes is called Cryolophosaurus (which means 'frozen crested reptile'), and was found in Antarctica. It is a meat-eating dinosaur but we do not know whether it migrated in during the summer months, or whether it lived there year round. Dinosaurs from polar latitudes have also been found in Alaska, but they are very similar to those from further south and are probably just a migrant population. The existence of dinosaurs at polar latitudes is significant. It means one of two things. Either dinosaurs had to hibernate or go into an inactive state in the polar winter. Or they had some way of maintaining a high body temperature - ie they were warm blooded. Many people think that some, if not all, dinosaurs were warm blooded. These polar discoveries are strong evidence for warm-bloodedness in at least some dinosaurs. This article was written to accompany episode five of Walking with Dinosaurs.
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