''Enhydra'' is a genus of mustelid that contains the

sea otter The sea otter (''Enhydra lutris'') is a marine mammal native to the coasts of the northern and eastern Pacific Ocean, North Pacific Ocean. Adult sea otters typically weigh between , making them the heaviest members of ...

and two extinct relatives. It is the only extant genus of the bunodont otters group, referring to otters with non-blade

carnassial Carnassials are paired upper and lower teeth modified in such a way as to allow enlarged and often self-sharpening edges to pass by each other in a shearing manner. This adaptation is found in carnivorans, where the carnassials are the modified f ...

s with rounded cusps. Sea otters probably diverged from other otters during the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58

'', a bunodont otter endemic to North America during the late

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

and early Pliocene epochs. ''

Enhydra reevei ''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 ...

'', the oldest known species, has its origins in the Atlantic, suggesting this may have been where sea otters originated. Fossil evidence indicates the ''Enhydra'' lineage became isolated in the

North Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the contine ...

approximately 2 million years ago, giving rise to the now-extinct ''

Enhydra macrodonta ''Enhydra macrodonta'', the large-toothed sea otter, is an extinct mustelid known from the middle Pleistocene in California. Description The large-toothed sea otter is a close relative of the living sea otter The s ...

'' and the modern sea otter.

References

Carnivoran genera Mammal genera with one living species Mustelidae Otters {{Carnivora-stub