Ontocetus

Ontocetus Temporal range: Miocene – Late Pleistocene PreЄ Є O S D C P T J K Pg N
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. This walrus is known from fragmentary but abundant fossils from the northern hemisphere. It lived from 13.6 mya—300,000 years ago, existing for approximately 13.3 million years, during the Miocene-Pleistocene. It was originally named Alachtherium by Du Bus in 1867.

Description

Ontocetus was a fairly big walrus that looked similar to todays walrus's with long protuding tusks and massive bodies. At least one species, Ontocetus posti, was also adapted to to suction-feeding. 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 a lot of blubber all over its body. Like all pinnipeds, it spent a significant part of its time at sea, although it could crawl onto land to rest and escape from predators.

Migrations and extinction

Appeared in the Miocene in the north of the Pacific Ocean, Ontocetus entered the Atlantic at the boundary of the Miocene and Pliocene, when the Isthmus of Panama had not yet been completely formed. Having reached western Europe and northwestern Africa (Morocco), this pinniped occupied a niche similar to modern walruses until it became extinct in the Early Pleistocene, unable to adapt to a cooling climate.

Paleoecology

In the Lower Pleistocene of Oosterschelde Estuary, the Netherlands, Ontocetus emmonsi was found alongside Odobenus and many other marine and terrestrial animals. Fishes (Eutrichiurides, Melanogrammus, Acipenser), earless seals (Phocanella) and cetaceans (Delphinapterus, Scaldicetus, Physeter, Balaenoptera) lived in the sea. Turtles (Emys), ducks and beavers (Trogontherium cuvieri and modern Castor fiber) inhabited rivers. Bovids (cattle, goats and extinct Bison priscus), cervids (Megaloceros, Eucladoceros, modern roe and red deers) rhinoceroses (Stephanorhinus, Coelodonta), horses (Equus robustus, Equus caballus) and proboscideans (mammoths, Anancus) grazed on land. These animals were hunted by bears, cave hyenas and humans.