SYSTEMATICS 



Evolution 



It has been supposed that the sea otter derived from an Atlantic 

 Ocean early Pleistocene ancestor Lutra reevei (Newton) (Thenius 

 and Hofer, 1960, p. 166). Recent findings in California of sea otter 

 remains from the early and late Pleistocene demonstrate that this 

 supposition is incorrect. Mitchell (1966, p. 1908) studied all avail- 

 able paleontological material. In his exhaustive review of the 

 fossils and literature he stated : 



Because these older North Pacific fossils are considered to be conspecific with 

 the living sea otter, it is obvious that the Lutra reevei tooth cannot represent 

 a direct ancestor of E. lutHs. . . . The sea otter may probably be con- 

 sidered as a strict North Pacific endemic autochthon, just as McLaren (1960) 

 has assumed it to be. 



Taylor (1914) studied the osteology and aquatic adaptations of 

 the sea otter and the river otter and concluded that the two otters 

 are fundamentally alike and probably descended from a common 

 ancestral form. Because the fossile record is incomplete, it is 

 possible only to speculate where the sea otter originated. Dr. 

 Charles A. Repenning suggests (letter, 3 March 1965) : 



I would guess that Enhydra developed from the otters of the Pliocene of 

 India and eastern Asia and moved northward along the western shore of the 

 North Pacific with the accentuation of global climatic zonality. All of the 

 otters of North America (including Enhydriodon) seem to be derived from 

 Asiatic stock and seem to have arrived in North America in the Pliocene and 

 early Pleistocene. 



Taxonomy 



The sea otter is the only member of the genus Enhydra. It is 

 the largest (to 100 lb. [45 kg.]) member of the family Mustelidae, 

 which includes nearly 70 species — river otters, skunks, weasels, 

 and badgers, among others. Unlike other mustelids, it has no func- 

 tional anal scent glands. The sea otter is the most specialized of 

 the group, being adapted to a narrow ecological zone in the marine 

 environment. Besides being the smallest marine mammal, it is 

 the only one in the order Carnivora. Among mammals it shares 

 the marine environment with the pinnipeds (seals), cetaceans 

 (whales and porpoises), and sirenians (manatees and dugongs). 



Miller and Kellogg (1955) and Hall and Kelson (1959) recognize 

 a northern race, Enhydra lutns lutris Linn., formerly ranging 



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