New Species of Fossil Otter at Hagerman

Brief History of Otters
Otters are members of the Mustelidae, a family that includes weasels and badgers. Otters first appeared in the Miocene of Europe and are represented by 13 living species. There are 6 species of otter found in the Americas today, including 4 river otters of the genus Lontra, the giant otter of South America, and the sea otter. Our new otter is at least 3.8 million years old and is the oldest example of the genus Lontra.

What’s in a name?
The genus name, Lontra, is used to show this otters relationship to American river otters. Its species name (weiri) distinguishes it from all other otters. Weiri is derived from the word “weir”, which is a river barrier that directs fish movement. The name reflects the otters’ diet of fish. It is also used here to honor Grateful Dead guitarist Bob Weir.

Why Is This Otter Important?
Ancestors of American otters entered North America from Eurasia by crossing the Bering Land Bridge. Paleontologists thought that this occurred in the Pleistocene, due to an absence of fossil American river otters in older deposits. Genetic studies of modern otters pointed to a much earlier origin, in the early Pliocene. Lontra weiri supports the genetic data. Advancements in paleontology are made with each new discovery as we slowly piece together the ancient history of life on earth!
Documentation of the New Species

Kari A. Prassack (2016): Lontra weiri, sp. nov., a Pliocene river otter
(Mammalia, Carnivora, Mustelidae, Lutrinae) from the Hagerman Fossil Beds (Hagerman
Fossil Beds National Monument), Idaho, U.S.A., Journal of Vertebrate Paleontology.

ABSTRACT—A new Pliocene river otter is described from the Hagerman Fossil Beds (Hagerman Fossil Beds National Monument), Idaho. Lontra weiri, sp. nov., exhibits notable lutrine traits that closely align it to Old World Lutra and New World Lontra, which are morphologically similar but diphyletic. It is further assigned to Lontra based on known otter biogeography and molecular phylogenetic data. The Hagerman Fossil Beds are characterized by a Blancan North American Land Mammal Age fauna, and radiometric dates for the otter-bearing deposits are inferred as >3.79 Ma, making this the first pre-Pleistocene occurrence of Lontra. Hagerman has a rich and diverse carnivoran fauna with at least five families and 17 species represented, including a much larger otter, Satherium piscinarium. This new otter increases carnivoran richness at Hagerman and provides insight into the evolution of New World river otters.
The Mustelidae are a widespread and diverse family that includes weasels, badgers, and otters. The otter subfamily, Lutrinae, has a long evolutionary history and speciose and widespread modern occurrence (Wilson and Reeder, 2005), but a poor fossil record (Willemsen, 1992, 2006; Baskin, 1998; Cherin and Rook, 2014). The fossil record of the New World river otter, Lontra, was previously limited to Pleistocene and Holocene occurrences of extant species (Gidley and Gazin, 1933; Corner, 1977; Kurten and Anderson, 1980; Anderson, 1984; Eshelman and Hager, 1984; Berta, 1995; Prevosti and Ferrero, 2008), and its origins and evolutionary relationships to other fossil otters are unclear. Lontra weiri, sp. nov., a Pliocene river otter from the Hagerman Fossil Beds, Idaho, provides insight into the evolution of New World river otters.

The full article can be retrived at

Last updated: October 7, 2017

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