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]

Enhydra Temporal range: 5–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓ Pliocene – Recent
Sea otter (Enhydra lutris)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Carnivora
Family:	Mustelidae
Subfamily:	Lutrinae
Genus:	Enhydra Fleming, 1828
Species
Enhydra lutris - Sea otter †Enhydra macrodonta †Enhydra reevei

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.