A water-loving mammal that lived 50 to 60 million years ago was probably the "missing link" between whales and hippos, according to a new analysis. Biologists have argued over the relationship between hippos and whales for a period of almost 200 years. The findings come from an analysis of features in different animal groups carried out by a US-French team. Their report is published in the science journal Proceedings of the National Academy of Sciences. Jean-Renaud Boisserie, Michel Brunet and Fabrice Lehoreau found that the semi-aquatic ancestor of whales and hippos split into two groups: cetaceans and the anthracotheres. Cetaceans...