Since the early 1980’s, the story of how whales walked into the sea has become one of the most celebrated of all evolutionary transitions. Pakicetus, Ambulocetus, Rodhocetus, and many, many more – these fossil whales with legs have beautifully demonstrated how land-dwelling mammals became adapted to life at sea. But, between 50 and 40 million years ago or so, whales were just going through a transition that many other vertebrate groups had gone through before. They were not the first vertebrates to return to the sea, nor were they the last, and a paper recently published in Paleobiology by paleontologists Johan Lindgren, Michael Polcyn, and Bruce Young has traced the history of how a very different group of animals got