A couple of weeks ago, I dreamed biologists discovered a species of orca that had re-evolved the ability to walk on land.
Their flippers had become muscular forelimbs. They had lost their thick layer of blubber as well as their "melon", the fatty spherical organ that gives dolphins their big rounded heads and plays a key role in echolocation. Their dorsal fins had become little more than ridges and their flukes were pairs of nubs at the end of their tails.
They had no hind limbs. Their bodies were balanced evenly on their forelimbs. They looked like weird black-and-white tyrannosaurs, only not as large, of course.