Here is all you need to know about the creodonts:
- They were a group of carnivorous mammals that, despite having carnassials, had no relation to Carnivora.
- They were a global force, occupying territories all across North America, Eurasia and Africa.
- They lived a long life, from 63 all the way to 11 million years ago.
Apparently, this clade became extinct not because of some dramatic environmental catastrophe, but because of competition with the carnivorans. But here's the deal--Carnivora did not occupy all the niches at once. The pinnipeds (seals, sea lions and walruses) did not debut until as recently as 24 million years ago.
So, in an alternate Earth, the creodonts managed to occupy the pinniped niche earlier in the Oligocene, millions of years before the carnivorans could. That way, by the time we get to the deadline of their extinction, those who were finfooted and semiaquatic would survive because there was nobody for them to compete with, indeed to as recently as the Holocene. Plausible or Not?