Secondly, look at any whale skeleton, and it will still have vestiges of hind limbs. It's pretty clear they either once had them, or are growing them. My money is on "had".
And the manatee has elephant style toe nails on its flippers, and has exactly zero use for them. They are vestiges of when it was a land mammal. Another one is the python that has a pelvis bone. Pelvis bones are for supporting hind legs. Most snakes have no trace of a pelvis bone, indicating that they transitioned into snakes much longer ago.
