I'd guess the ancestor was some thing resembling a hippo, like these sea surfing hippos from West Africa: https://youtu.be/ZvyBmXn7Euc https://youtu.be/ZvyBmXn7

I'd guess the ancestor was some thing resembling a hippo, like these sea surfing hippos from West Africa: https://youtu.be/ZvyBmXn7Euc https://youtu.be/ZvyBmXn7Euc Also see this informative graphic: https://www.juneauwhalewatch.com/wp-content/uploads/2017/07/Whippos.jpg https://www.juneauwhalewatch.com/wp-content/uploads/2017/07/...