Ontocetus
{{Short description|Extinct genus of carnivorans}}
{{Automatic taxobox
| fossil_range = Miocene to Late Pleistocene, {{fossil_range|13.6|0.3}}
| image = Ontocetus emmonsi.jpg
| image_caption = Specimen of O. emmonsi that was once the holotype of Alachtherium cretsii
| taxon = Ontocetus
| parent_authority = Leidy, 1859
| type_species = O. emmonsi
| authority = Leidy, 1859
| subdivision_ranks = Species
| subdivision = {{specieslist
|O. emmonsi|Leidy, 1859
|O. posti|Boisville, Chatar & Kohno, 2024
}}
}}
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 {{Mya|13.6-0.3|million years}}.[https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=36786 PaleoBiology Database: Ontocetus, basic info]
Taxonomy
The type species, Ontocetus emmonsi, was named by Joseph Leidy in 1859 on the basis of a single tusk-like tooth (USNM 329064) collected by Ebenezer Emmons from the early Pliocene (Zanclean) Yorktown Formation of North Carolina.{{cite journal | author = Leidy J | year = 1859 | title = [Remarks on Dromatherium sylvestre and Ontocetus emmonsi] | journal = Proceedings of the Academy of Natural Sciences of Philadelphia | volume = 1859 | page = 162 }}
In the meantime, marine mammals fossils were being unearthed in Neogene deposits in the vicinity of Antwerp, Belgium as well as Suffolk, England. One of these fossils was identified as an odobenid and named Alachtherium cretsii. in 1867.B. Du Bus. 1867. Sur quelques mammiferes du crag d'Anvers. Bulletins de L'Academie Royale des Sciences, des Lettres et des Beaux-Arts 24:562-577 An isolated tooth (RBINS 2892) was named Trichechodon koninckii in 1871.P. J. Van Beneden. 1871. Les Phoques de la mer scaldisienne. Bulletins de L'Academie Royale des Sciences, des Lettres det des Beaux-Arts de Belgique 32:5-18 The fossils from Suffolk were named Trichechodon huxleyi in 1865.{{cite journal | author = Lankester E. R. | year = 1865 | title = On the sources of the mammalian fossils of the Red Crag, and the discovery of a new mammal in that deposit, allied to the walrus | url = https://zenodo.org/record/1448513| journal = Quarterly Journal of the Geological Society of London | volume = 21 | issue = 1–2| pages = 221–232 | doi=10.1144/gsl.jgs.1865.021.01-02.28| s2cid = 130245053 }} For decades, however, Ontocetus was tossed aside as a physeterid, as the type specimen was believed to have been missing.{{cite journal | author = Kellogg R | year = 1925 | title = A fossil physeteroid cetacean from Santa Barbara County California | doi = 10.5479/si.00963801.66-2564.1 | journal = Proceedings of the United States National Museum | volume = 66 | issue = 27| pages = 1–8 }} For example, Ontocetus was at one time considered a synonym of the physeterid Hoplocetus.E. L. Trouessart. 1898. Catalogus mammalium tam viventium quam fossilum 5:665-1264 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.G. Hasse. 1909. Les Morses Pliocène poederlien à Anvers. Bulletin de la Société Belge de Géologie de Paléontologie et d'Hydrologie (Bruxelles) 23:293-322{{cite journal | author = Rutten L | year = 1907 | title = On fossil trichechids from Zeeland and Belgium | journal = Proceedings of the Royal Netherlands Academy of Arts and Sciences | volume = 10 | issue = 1| pages = 2–14 }}{{cite journal|last1=Berry|first1=E. W.|last2=Gregory|first2=W. K.|title=Prorosmarus alleni, a new genus and species of walrus from the upper Miocene of Yorktown, Virginia|journal=American Journal of Science|date=1906|volume=21|issue=126|pages=444–450|doi=10.2475/ajs.s4-21.126.444|bibcode=1906AmJS...21..444B|url=https://zenodo.org/record/1450148}}{{cite journal | author = Geraads D | year = 1997 | title = Carnivores du Pliocene terminal de Ahl al Oughlam (Casablanca, Maroc) | journal = Géobios | volume = 30 | issue = 1| pages = 127–164 | doi=10.1016/s0016-6995(97)80263-x| bibcode = 1997Geobi..30..127G }}
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.{{cite journal | author = Kohno N., Ray C. E. | year = 2008 | title = Pliocene walruses from the Yorktown Formation of Virginia and North Carolina, and a systematic revision of the North Atlantic Pliocene walruses | journal = Virginia Museum of Natural History Special Publication | volume = 14 | pages = 39–80 }}
In 2024, reassessment of a pair of mandibles from the UK and a mandible from Belgium that had been assigned to O. emmonsi resulted in the establishment of a second species in the genus, O. posti.{{cite journal|last1=Boisville|first1=M|last2=Chatar|first2=N|last3=Kohno|first3=N.|year=2024|title=New species of Ontocetus (Pinnipedia: Odobenidae) from the Lower Pleistocene of the North Atlantic shows similar feeding adaptation independent to the extant walrus (Odobenus rosmarus)|journal=PeerJ|volume=12|pages=e17666|doi=10.7717/peerj.17666|doi-access=free|pmc=11328838}}
=Misassigned species=
O. oxymycterus was named by Remington Kellogg in 1925 on the basis of USNM 10923, collected from the middle Miocene (Serravallian) Monterey Formation in Santa Barbara, California. 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.{{Cite journal|author1=Alexandra T. Boersma|author2=Nicholas D. Pyenson|author2-link=Nicholas Pyenson |year=2015 |title=Albicetus oxymycterus, a New Generic Name and Redescription of a Basal Physeteroid (Mammalia, Cetacea) from the Miocene of California, and the Evolution of Body Size in Sperm Whales |journal=PLOS ONE |volume=10 |issue=12 |pages=e0135551 |doi=10.1371/journal.pone.0135551 |pmid=26651027 |pmc=4674121|bibcode=2015PLoSO..1035551B |doi-access=free }}
References
{{Reflist|30em}}
- 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
{{Pan-Pinnipedia|O.}}
{{Taxonbar|from=Q7095037}}
Category:Pleistocene pinnipeds
Category:Prehistoric carnivoran genera
Category:Prehistoric mammals of Europe
Category:Prehistoric pinnipeds of North America