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NORTH AMERICAN FAUNA 74 



developmental characteristics of individuals, their food and feeding, reproduc- 

 tion, mortality, and finally, my views on the history and current status of the 

 population. 



Systematics and Taxonomy 



The seals, sea lions, and walruses of the world have been regarded for a long 

 time as constituting a single order or suborder of carnivorous mammals, known 

 as the Pinnipedia Illiger, 1811. Each of these subgroups of pinnipeds bears 

 superficial resemblance to the others in the possession of a fusiform body and, as 

 the name signifies, webbed, fin-like appendages. The proximal half or more of 

 each limb is enclosed in the relatively thick skin-envelope of the body; ear pinnae 

 are mostly absent or greatly reduced; a thick layer of fat (blubber) underlies the 

 skin; and the adult pelage of all but the fur seals generally is more short, coarse, 

 and sparse than that of their terrestrial relatives, the fissiped carnivores (Scheffer 

 1958, 1964). 



The possibility of derivation of the Pinnipedia from more than one line of an- 

 cestral canoid carnivores has long been debated (e.g., see McLaren 1960) and 

 now seems virtually certain (Tedford 1976). Hence, a new classification has been 

 proposed, which takes into consideration these newly recognized relationships 

 (Tedford 1976:372; Repenning and Tedford 1977:8). For the living pinnipeds, 

 this classification is as follows: 



Order Carnivora Bowdich, 1821 

 Suborder Caniformia Kretzoi, 1943 

 r Superfamily Otarioidea Gill, 1866 



Family Otariidae Gill, 1866 (fur seals and sea lions) 

 Family Odobenidae Allen, 1880 (walruses) 

 Superfamily Musteloidea Swainson, 1835 

 Family Phocidae Gray, 1825 (hair seals) 



Repenning and Tedford (1977) have traced the Odobenidae to a common 

 origin with the Otariidae in the early Miocene, some 20 million years ago 

 (Fig. 2), from an aquatic ancestral group (Enaliarctidae Mitchell and Tedford, 

 1973) having close affinity to primitive ursine (bear-like) carnivores. Those 

 origins were in the North Pacific Ocean, whereas it seems likely that the hair 

 seals or Phocidae were derived somewhat earlier from an otter-like ancestor, 

 probably in the European sector of the North Atlantic Ocean (Ray 1976). The 

 primitive walrus-like pinnipeds evidently flourished and became greatly 

 diversified in late Miocene-early Pliocene times, but only one form has survived 

 to the present, the living walrus, Odobenus rosmarus Linnaeus, 1758. The 

 ancestor of this form apparently made its way from the Pacific to the Atlantic via 

 the Central American Seaway between 5 and 8 million years ago; some time 

 later, the Pacific stock(s) became extinct. The modern walruses of the North 

 Pacific region were derived from the Atlantic stock, having made their way back 

 to the Pacific via the Arctic Ocean sometime within the last million years 

 (Repenning 1976). 



