Baby Seal, Lake Baikal, Siberia, Russia

The otter-like mustelid Potamotherium may actually represent an even earlier phase in the evolution of pinnipeds.
Another (more advanced) early pinniped is Enaliarctos, which lived 24 – 22 million years ago. It is believed to have been a good swimmer, but to have been able to move on land as well as in water, more like an otter than like modern pinnipeds. There has been longstanding debate as to whether walruses diverged from a common otariid-phocid ancestor, or whether the phocids diverged before a common otariid-odobenid ancestor. The most recent evidence suggest that the latter hypothesis is more likely.