Marine Biology

SUBORDER PINNIPEDIA - Seals, Sea lions, and Walruses

         There are 34 species of pinnipeds assigned to 3 families of the mammalian order Carnivora: the Otariidae, Phocidae and Odobenidae. The otariids include the 14 species of sea lions and fur seals, sometimes referred to as the eared or walking seals. The phocids include the 19 species of true seals, sometimes referred to as the earless true, or crawling seals. Odobenid  is reduced to just a single living species, the walrus. There is controversy as to whether the pinnipeds are monophyletic (i.e.,evolved from a single ancestor) or biphyletic (from 2 separate ancestors).

        Pinnipeds are highly specialized aquatic carnivores that live in a diversity of marine habitats, and some freshwater ones as well. One unifying feature of the group is that all must return to a solid substrate, such as land or ice, to bear their pups. Females give birth to a single offspring per reproductive effort. Twins are extremely rare in all species. All species are amphibious, though the otariids are the most agile and mobile on land. In general, phocids are more capable divers and breath-holders, although there is overlap in the capabilities of some otariids and phocids. Some species spend considerable amount of time in the water, only coming ashore to breed or give birth.          

         Pinnipeds all have fur (but also use blubber for thermoregulation), 2 sets of limbs (called foreflippers and hindflippers), long whiskers, nasal openings at the tip of the snout, and reduced or lost ear flaps. Pinnipeds moult every year, some gradually over several weeks or months, others dramatically in a short time. In most species pups are born in a lanugo coat which differ from juvenile or adult pelage in colour and length.