Journal of Mammalian Evolution

, Volume 25, Issue 1, pp 27–35 | Cite as

A Middle Pleistocene Sea Otter from Northern California and the Antiquity of Enhydra in the Pacific Basin

  • Robert W. Boessenecker
Original Paper


Extant sea otters (Enhydra lutris) are remarkably well understood in terms of behavior, ecology, and interactions with humans, but the evolutionary history of this charismatic marine mammal is limited owing to a fragmentary fossil record. Disagreements over the generic assignment of various fossil otter remains to members of the tribe Enhydrini, and limited geochronologic data for these records have impeded attempts to interpret the evolutionary biogeography of Enhydra. A well-preserved femur of Enhydra sp. from a middle Pleistocene horizon within the Merced Formation of northern California is the oldest record of Enhydra in the Pacific with robust geochronologic age control. Bracketing 87Sr/86Sr dates indicate an age of 620–670 ka. Reappraisal of the geochronologic age of various occurrences of Enhydrini indicate dispersal of Enhydra into the Pacific through the Bering Strait no earlier than the middle Pleistocene. Somewhat older early Pleistocene fossils of Enhydra from Alaska and England suggest an Arctic or North Atlantic origin of the Enhydra lineage.


Enhydra Lutrinae Sea otter Pleistocene Pacific 



First and foremost, I am indebted to C.S. Pirrone for collecting, donating, and mailing the specimen to New Zealand for preparation and study. This study benefited from comments by J. Corrie, and discussions with M. Churchill, J. Corrie, R.E. Fordyce, C.H. Tsai, and Y. Tanaka. Thanks to D.J. Bohaska, J. Demouthe, M. Goodwin, P.A. Holroyd, N. D. Pyenson, and W. Miller, III, for access to museum collections and specimens under their care. Thanks to R.E. Fordyce and S. White for assistance with preparation and access to laboratory facilities, and thanks to P. Holroyd for curatorial assistance. The author was supported by a University of Otago Doctoral Scholarship during this study.


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Copyright information

© Springer Science+Business Media New York 2016

Authors and Affiliations

  1. 1.Department of Geology and Environmental GeosciencesCollege of CharlestonCharlestonUSA
  2. 2.Museum of PaleontologyUniversity of CaliforniaBerkeleyUSA

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