What fundamental adaptation allows fur seals to walk or run on all fours when hauled out on land?

Answer

Hind flippers that can rotate forward beneath their bodies

Fur seals possess hind flippers capable of rotating forward beneath their bodies, granting them the agility to walk or run terrestrially, a mobility true seals lack.

What fundamental adaptation allows fur seals to walk or run on all fours when hauled out on land?
mammaladaptationPinnipedFur Seal