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. Hippos are the last of a mammal group that
thrived for 40 million years 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 eventually spurned land, lost their
legs and became fully aquatic. The pig-like anthracotheres,
flourished over 40 million years and died out less than 2.5
million years ago. They left only one descendent: the
hippopotamus. The study places whales firmly within the cloven-
hoofed group of mammals known as Artio