Even though the mesonychids seem to be cousins of today’s even-toed ungulates (and there are reasons for believing this over and above their hooves) they are no closer to hippos than they are to all the rest of the cloven-hoofed animals. We keep coming back to the molecular shocker: whales are not just cousins of all the artiodactyls, they are buried within the artiodactyls, closer to hippos than hippos are to cows and pigs.
