Seals and sea lions part ways
The pinnipeds divide into the ones that swim with their front flippers and the ones that use their back.
- When
- —
- Duration
- 5 million years
- Known to
- ± 2 million years
- Era
- Miocene, Cenozoic
Early in the Miocene the pinnipeds split into otariids — fur seals and sea lions, which row with large foreflippers and can rotate their hind limbs forward to walk on land — and phocids, the true seals, which propel themselves with alternating strokes of the hind flippers and are reduced to hauling themselves along on shore. Walruses branch separately. The two swimming modes are a clean example of the same problem being solved twice from the same starting anatomy.