''Ontocetus'' is an extinct genus of

walrus The walrus (''Odobenus rosmarus'') is a large pinniped, flippered marine mammal with a discontinuous distribution about the North Pole in the Arctic Ocean and subarctic seas of the Northern Hemisphere. The walrus is the only living species in ...

, an aquatic

carnivoran Carnivora is a monophyletic order of placental mammals consisting of the most recent common ancestor of all cat-like and dog-like animals, and all descendants of that ancestor. Members of this group are formally referred to as carnivorans, ...

of the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Odobenidae Odobenidae is a family of pinnipeds. The only living species is the walrus (''Odobenus rosmarus''). In the past, however, the group was much more diverse, and includes more than a dozen fossil genera. Taxonomy All genera, except ''Walrus, Odob ...

, endemic to coastal regions of the southern

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

and the southeastern coastal regions of the U.S. during the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

. It lived from 13.6 mya—300,000 years ago, existing for approximately .

Taxonomy

The type species, ''Ontocetus emmonsi'', was named by

Joseph Leidy Joseph Mellick Leidy (September 9, 1823 – April 30, 1891) was an American paleontologist, parasitologist and anatomist. Leidy was professor of anatomy at the University of Pennsylvania, later was a professor of natural history at Swarthmore ...

in 1859 on the basis of a single tusk-like tooth (USNM 329064) collected by

Ebenezer Emmons Ebenezer Emmons (May 16, 1799October 1, 1863), was a pioneering American geologist whose work includes the naming of the Adirondack Mountains in New York as well as a first ascent of Mount Marcy. Early life Emmons was born at Middlefield, Massa ...

from the early

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Zanclean The Zanclean is the lowest stage or earliest age on the geologic time scale of the Pliocene. It spans the time between 5.332 ± 0.005 Ma (million years ago) and 3.6 ± 0.005 Ma. It is preceded by the Messinian Age of the Miocene Epoch, and fol ...

)

Yorktown Formation The Yorktown Formation is a mapped bedrock unit in the Coastal Plain of Maryland, Virginia, North Carolina and South Carolina. It is overconsolidated and highly fossiliferous. Description The Yorktown is composed largely of overconsolidated san ...

North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and So ...

. In the meantime, marine mammals fossils were being unearthed in

Neogene The Neogene ( ), informally Upper Tertiary or Late Tertiary, is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period Mya. ...

deposits in the vicinity of

Antwerp Antwerp (; nl, Antwerpen ; french: Anvers ; es, Amberes) is the largest city in Belgium by area at and the capital of Antwerp Province in the Flemish Region. With a population of 520,504,

Belgium Belgium, ; french: Belgique ; german: Belgien officially the Kingdom of Belgium, is a country in Northwestern Europe. The country is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeast, France to th ...

as well as

Suffolk Suffolk () is a ceremonial county of England in East Anglia. It borders Norfolk to the north, Cambridgeshire to the west and Essex to the south; the North Sea lies to the east. The county town is Ipswich; other important towns include Lowes ...

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

. One of these fossils was identified as an odobenid and named ''Alachtherium cretsii.'' in 1867. An isolated tooth (RBINS 2892) was named ''Trichechodon koninckii'' in 1871. The fossils from Suffolk were named ''Trichechodon huxleyi'' in 1865. For decades, however, ''Ontocetus'' was tossed aside as a physeterid, as the type specimen was believed to have been missing. For example, ''Ontocetus'' was at one time considered a synonym of the physeterid '' Hoplocetus''. In the meantime, further Pliocene walrus fossils were collected from the North Atlantic, including the holotypes of ''Alachitherium antverpiensis'', ''Alachitherium antwerpiensis'', ''Prorosmarus alleni'', and ''Alachitherium africanum''. In 2008, all specimens of Pliocene odobenids from the North Atlantic region were reviewed following the rediscovery of the ''Ontocetus emmonsi'' holotype in the 1990s. ''T. huxleyi'', ''A. cretsii'', ''A. antwerpiensis'', ''A. antverpiensis'', ''A. africanum'', and ''P. alleni'' were declared junior synonyms of ''O. emmonsi'' based on comparisons with USNM 329064. ''T. koninckii'', however, was found to be undiagnostic and designated a ''

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium'' it may be impossible to determine whether a s ...

''.

Misassigned species

As a side note, ''Ontocetus oxymycterus'' was named by

Remington Kellogg Arthur Remington Kellogg (5 October 1892 – 8 May 1969) was an American naturalist and a director of the United States National Museum. His work focused on marine mammals. Early life and career Kellogg was born in Davenport, Iowa, and quick ...

in 1925 on the basis of USNM 10923, collected from the middle

(

Serravallian The Serravallian is, in the geologic timescale, an List of time periods, age or a stage (stratigraphy), stage in the middle Miocene epoch (geology), Epoch/series (stratigraphy), Series, which spans the time between 13.82 annum, Ma and 11.63 Ma (m ...

) Monterey Formation in Santa Barbara,

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

. It was recombined as ''Scaldicetus oxymycterus'' by Kohno and Ray (2008), since ''O. emmonsi'' was odobenid and ''O. oxymycterus'' was physeteroid. Boersma and Pyenson (2015) made it the type species of the genus ''

Albicetus ''Albicetus'' is a genus of stem-sperm whales that lived during the Miocene Epoch, around 15 million years ago, and was discovered in Santa Barbara, California in 1909. It was categorized for decades as belonging to a group of extinct walruses e ...

''.

References

*''Evolution: What the Fossils Say and Why It Matters'' by Donald R. Prothero and Carl Buell *''Marine Mammals: Evolutionary Biology'' by Annalisa Berta, James L. Sumich, and Kit M. Kovacs {{Taxonbar, from=Q7095037 Pliocene pinnipeds Miocene pinnipeds Pleistocene pinnipeds Prehistoric carnivoran genera Prehistoric mammals of Europe Prehistoric pinnipeds of North America Odobenids Fossil taxa described in 1859 Taxa named by Joseph Leidy