Enhydra is a genus of mustelid that contains the sea otter and two extinct relatives. It is the only extant genus of the bunodont otters group, referring to otters with non-blade carnassials with rounded cusps.[1]
Sea otters probably diverged from other otters during the Pliocene, approximately 5 mya.[2] They probably arose from the closely related Enhydritherium, a bunodont otter endemic to North America during the late Miocene and early Pliocene epochs.[1]
Enhydra reevei, the oldest known species, has its origins in the Atlantic, suggesting this may have been where sea otters originated.[2] Fossil evidence indicates the Enhydra lineage became isolated in the North Pacific approximately 2 million years ago, giving rise to the now-extinct Enhydra macrodonta and the modern sea otter.
