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

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