Between 200 and 65 million years ago, fearsome marine reptiles reigned over the oceans. Were they warm-blooded like today's mammals and birds or cold-blooded like nowadays fish and reptiles? For the first time, a study has settled the debate: some large marine reptiles were warm-blooded (in other words, they were endothermic), giving them a considerable advantage to swim fast over long distances and to conquer cold regions....