Thirty-two teeth of the dinosaur species Camarasaurus, a common sauropod found in North America, were examined leading to new data about its life. The teeth provided evidence that these sauropods migrated from their normal habitats the flood plains during the dry seasons in search of food. These migration patterns are incredibly relevant because they could potentially be one of the evolutionary explanations for why the sauropods reached such large sizes. It is possible that something referred to as a feedback process occurred: the larger sauropods became, the easier it would be for them to migrate and get more food, and the more food they got due to migration, the larger they grew, therefore leading to an overall growth in size of the species. Through measuring the oxygen isotopes found within the various enamels of the fossilized teeth, scientists are trying to put together the sauropod migration patterns, which will hopefully provide even more information about their evolution.

http://www.guardian.co.uk/science/2011/oct/26/large-dinosaurs-migrated-huge-distances