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Temporal range: Miocene – Late Pleistocene
Reconstrucciones-prehistoricas-kennis 11 715660.jpg
An artist's illustration of Ontocetus emmonsi
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Suborder: Caniformia
Superfamily: Pinnipedia
Family: Odobenidae
Genus: Osbornoceros
Leidy, 1859
Binomial name
Ontocetus emmonsi
Leidy, 1859

Ontocetus is an extinct genus of walrus, an aquatic carnivoran of the family Odobenidae, endemic to coastal regions of the southern North Sea and the southeastern coastal regions of the U.S. during the Miocene-Pleistocene. It lived from 13.6 mya—300,000 years ago, existing for approximately 13.3 million years. It was originally named Alachtherium by Du Bus in 1867.


Ontocetus was a fairly big walrus that looked similar to todays walrus's with long protuding tusks and massive bodies. It may have used its tusks in its jaws to fight for mates or to warn off predators. Ontocetus may also have used its front flippers to pull itself across the Arctic lands of the North Sea and coastal regions of the USA. Its name possibly means "Beach Whale" and had quite alot of blubber alll over its body to keep Ontocetus warm in the Artic tundra of the ice age.