Ontocetus is an extinct genus ofwalrus, anaquaticcarnivoran of thefamilyOdobenidae, endemic to coastal regions of the southernNorth Sea and the southeastern coastal regions of the U.S. during theMiocene-Pleistocene. It lived from 13.6mya—300,000 years ago, existing for approximately13.3 million years.[1]
| Ontocetus | |
|---|---|
 | |
| Specimen ofO. emmonsi that was once theholotype ofAlachtherium cretsii | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Carnivora |
| Parvorder: | Pinnipedia |
| Family: | Odobenidae |
| Subfamily: | Odobeninae Leidy, 1859 |
| Genus: | †Ontocetus Leidy, 1859 |
| Type species | |
| O. emmonsi | |
| Species | |
| |
Taxonomy
editThe type species,Ontocetus emmonsi, was named byJoseph Leidy in 1859 on the basis of a single tusk-like tooth (USNM 329064) collected byEbenezer Emmons from the earlyPliocene (Zanclean)Yorktown Formation ofNorth Carolina.[2]
In the meantime, marine mammals fossils were being unearthed inNeogene deposits in the vicinity ofAntwerp,Belgium as well asSuffolk,England. One of these fossils was identified as an odobenid and namedAlachtherium cretsii. in 1867.[3] An isolated tooth (RBINS 2892) was namedTrichechodon koninckii in 1871.[4] The fossils from Suffolk were namedTrichechodon huxleyi in 1865.[5] For decades, however,Ontocetus was tossed aside as aphyseterid, as the type specimen was believed to have been missing.[6] For example,Ontocetus was at one time considered a synonym of the physeteridHoplocetus.[7] In the meantime, further Pliocene walrus fossils were collected from the North Atlantic, including the holotypes ofAlachitherium antverpiensis,Alachitherium antwerpiensis,Prorosmarus alleni, andAlachitherium africanum.[8][9][10][11]
In 2008, all specimens of Pliocene odobenids from the North Atlantic region were reviewed following the rediscovery of theOntocetus emmonsi holotype in the 1990s.T. huxleyi,A. cretsii,A. antwerpiensis,A. antverpiensis,A. africanum, andP. alleni were declared junior synonyms ofO. emmonsi based on comparisons with USNM 329064.T. koninckii, however, was found to be undiagnostic and designated anomen dubium.[12]
In 2024, reassessment of a pair of mandibles from the UK and a mandible from Belgium that had been assigned toO. emmonsi resulted in the establishment of a second species in the genus,O. posti.[13]
Misassigned species
editO. oxymycterus was named byRemington Kellogg in 1925 on the basis ofUSNM 10923, collected from the middleMiocene (Serravallian) Monterey Formation inSanta Barbara,California.[6] It was recombined asScaldicetus oxymycterus by Kohno and Ray (2008), sinceO. emmonsi was odobenid andO. oxymycterus was physeteroid.[12] Boersma and Pyenson (2015) made it the type species of the genusAlbicetus.[14]
References
edit- ^PaleoBiology Database:Ontocetus, basic info
- ^Leidy J (1859). "[Remarks on Dromatherium sylvestre and Ontocetus emmonsi]".Proceedings of the Academy of Natural Sciences of Philadelphia.1859: 162.
- ^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
- ^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
- ^Lankester E. R. (1865)."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".Quarterly Journal of the Geological Society of London.21 (1–2):221–232.doi:10.1144/gsl.jgs.1865.021.01-02.28.S2CID 130245053.
- ^abKellogg R (1925). "A fossil physeteroid cetacean from Santa Barbara County California".Proceedings of the United States National Museum.66 (27):1–8.doi:10.5479/si.00963801.66-2564.1.
- ^E. L. Trouessart. 1898. Catalogus mammalium tam viventium quam fossilum 5:665-1264
- ^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
- ^Rutten L (1907). "On fossil trichechids from Zeeland and Belgium".Proceedings of the Royal Netherlands Academy of Arts and Sciences.10 (1):2–14.
- ^Berry, E. W.; Gregory, W. K. (1906)."Prorosmarus alleni, a new genus and species of walrus from the upper Miocene of Yorktown, Virginia".American Journal of Science.21 (126):444–450.Bibcode:1906AmJS...21..444B.doi:10.2475/ajs.s4-21.126.444.
- ^Geraads D (1997). "Carnivores du Pliocene terminal de Ahl al Oughlam (Casablanca, Maroc)".Géobios.30 (1):127–164.Bibcode:1997Geobi..30..127G.doi:10.1016/s0016-6995(97)80263-x.
- ^abKohno N., Ray C. E. (2008). "Pliocene walruses from the Yorktown Formation of Virginia and North Carolina, and a systematic revision of the North Atlantic Pliocene walruses".Virginia Museum of Natural History Special Publication.14:39–80.
- ^Boisville, M; Chatar, N; Kohno, N. (2024)."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)".PeerJ.12: e17666.doi:10.7717/peerj.17666.PMC 11328838.
- ^Alexandra T. Boersma;Nicholas D. Pyenson (2015)."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".PLOS ONE.10 (12): e0135551.Bibcode:2015PLoSO..1035551B.doi:10.1371/journal.pone.0135551.PMC 4674121.PMID 26651027.
- 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