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. Sea otters probably diverged from other otters during the Pliocene, approximately 5 mya. They probably arose from the closely related Enhydritherium, a bunodont otter endemic to North America during the late Miocene and early Pliocene epochs.