Order - Carnivora
The scientific order Carnivora includes all mammals belonging to the dog, cat, and bear families, as well as raccoons and otters.
Family - Mustelidae
All otters belong to the family Mustelidae, along with weasels, skunks, minks, and badgers. Mustelids are characterized by generally long, streamlined bodies; fine, dense hair; and scent glands at the base of the tail.
Genus - Lutra (river otters).
- North American river otter (Lutra canadensis)
- marine otter (Lutra felina)
- neotropical/long-tailed otter (Lutra longicaudus)
- Eurasian otter (Lutra lutra)
- spot-necked otter (Lutra maculicollis)
- smooth/smooth-coated otter (Lutra perspicillata)
- southern river otter (Lutra provocax)
- hairy-nosed otter (Lutra sumatrana)
Genus - Pteronura (giant otter).
- giant otter (Pteronura brasiliensis)
Genus - Aonyx (clawless otters).
- Cape clawless otter (Aonyx capensis)
- Asian small-clawed otter (Aonyx cinerea)
- Congo clawless otter (Aonyx congica)
Genus - Enhydra (sea otter).
- sea otter (Enhydra lutris)
- Sea otters are further divided into three subspecies:
- E.l. lutris - the Russian or Asian sea otter
- E.l. kenyoni - the northern or Alaskan sea otter
- E.l. nereis - the southern or California sea otter.
- The subspecies are separated geographically, and vary slightly in their size, diet, use of tools, and the amount of time they spend on land.
The fossil remnants of many freshwater otters date back to the Miocene (5 to 23 million years ago).
Scientists believe that sea otters descended from fish-eating, otter-like ancestors about five to seven million years ago, during the late Miocene and early Pliocene period.