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Squalodon

From Wikipedia, the free encyclopedia

Extinct genus of mammals

Squalodon Temporal range:Oligocene–Miocene PreꞒ Ꞓ O S D C P T J K Pg N

Skull ofS. bariensis at theMuseum of Natural Sciences in Brussels.
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Artiodactyla
Infraorder:	Cetacea
Superfamily:	Platanistoidea
Family:	†Squalodontidae Brandt, 1873
Genus:	†Squalodon Grateloup, 1840
Type species
†Squalodon grateloupii von Meyer, 1843
Species
†S. antverpiensis(van Beneden, 1861) †S. bariensis(Jourdan, 1861) †S. barbarus(Mchedlidze and Aslanova, 1968) †S. calvertensis(Kellogg, 1923) †S. whitmorei(Dooley, 2005) †S. catulli(Molin, 1859)

Squalodon is anextinct genus ofwhales of theOligocene andMiocene epochs, belonging to thefamily Squalodontidae. Named byJean-Pierre Sylvestre de Grateloup in 1840,^[1] it was originally believed to be aniguanodontid dinosaur but has since been reclassified. The nameSqualodon comes fromSqualus, a genus of shark. As a result, its name means "shark tooth". Its closest modern relatives are the 2 species of the genusPlatanista ( theGanges river dolphin andIndus river dolphin).^[2]^[3]

Description

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Species ofSqualodon areodontocetes that lived during the late Oligocene into the middle Miocene, about 28 to 15 million years ago.^[2] The genusSqualodon belongs to the order Odontoceti, the toothed whales. Their name is derived from the termSqualus because their cheek teeth were thought to resemble the teeth of aSqualus shark. The largest species,Squalodon whitmorei, reached up to 5.5 meters in length.^[4] The unique-looking squalodontids were likely distributed throughout the world in warm waters during the Oligocene and Miocene. Squalodontidae became extinct in the middle of the Miocene, leaving no descendants. Hypotheses of why this family lead to extinction have to deal with competition of other groups of dolphins as well as climate change.

These whales are characterized by both ancestral and modern features. Their teeth are the most evident ancestral feature. At this time in history other toothed whales were evolving simple conical teeth while Squalodontidae retained their primitive dentition that their ancestors (the archaeocetes) had developed.^[5] Today living odontocetes have little variation in their teeth. Squalodontids' teeth are much more complex: they are widely spaced apart; their cheek teeth are triangular and serrated for grasping and cutting. Due to the efficiency of their primitive dentition squalodontids could have a diverse variety of prey. Another ancestral quality of the Squalodontidae is their necks. Squalodontid necks are more compressed than their ancestors, the Archaeoceti. Compared to toothed whales at that time, the squalodontids were likely more mobile. Paleontologists also believe that the dorsal fins were reduced but larger than that of the ancestors.^[5] Shark toothed whales also possess many modern features. Their crania were well compressed, their rostrums were telescoped outward, and their skulls show proof of the origin of echolocation.^[6] InS. grateloupii, the rostrum made up more than 60% of the total length of its skull.^[7]

Fossil record and classification

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Fossils of this genus are identified mainly by the teeth but several different species have been named based on skull characteristics and size (the biggest being S. whitmorei). Most of the fossil record consists of teeth. These odontocete fossils have been discovered in Europe, eastern North America, New Zealand, and Argentina. Because isolated teeth are insufficient for species identification, most specimens lacking the skull can only be identified to genus.^[8] The fossils of squalodontids indicate that this species is more closely related to endangered species of dolphins and not to most of the living dolphins today.^[9]

The systematic placement ofSqualodon within Odontoceti was long unclear. For a long time, it was thought to be close of the ancestry of modern dolphins and porpoise.^[10] Many of the fresh-water dolphins are differentiated phylogenetically very well, while the argument of some of the species has been going on for more than a century. The taxon is characterized during the Oligocene and Miocene in which heterodont teeth are standard amongst the family. Some modern features of the scapula, however, contradict with current phylogenetic relationships. Squalodontids were believed to be the last common ancestor of the odontocetes until 1984. Muizon came to the conclusion that rather than to any of the living species this family is closer related to the endangered species. Therefore, the ancestry of today's dolphins has little to do with the squalodontids.^[9]

Species

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As the type genus of Squalodontidae,Squalodon has become a repository for various squalodontids or even taxa that were once thought to belong to Squalodontidae. However, there has been no revision ofSqualodon.

Species currently recognized as valid

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Squalodon grateloupii Meyer, 1843 (type species)
Squalodon antverpiensis van Beneden, 1861
Squalodon barbarus Mchedlidze and Aslanova 1968
Squalodon calvertensis Kellogg 1923
Squalodon whitmorei Dooley 2005
Squalodon catulli Molin 1859

Questionably or originally assigned toSqualodon

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Arionus servatus Meyer, 1841 =Squalodon meyeri Brandt, 1873
Pachyodon mirabilis Meyer, 1838
Rhytisodon tuberculatus Costa, 1852
Smilocamptus burgueti Gervais, 1859
Phocodon melitensis (Blainville, 1840) =Phoca melitensis Blainville, 1840 =Phocodon scillae Agassiz, 1841
"Squalodon" kelloggi Rothausen, 1968
Squalodon bariensis Jourdan 1861^[7]
Squalodon bellunensis Dal Piaz, 1901
Squalodon peregrinus Dal Piaz, 1971
Squalodon imperator Cigala-Fulgosi & Pilleri, 1985
Squalodon gambierensisGlaessner 1955^[11]

References

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^Grateloup,Description d'un fragment de mâchoire fossile, d'un genre nouveau de reptile (Saurien), de taille gigantesque, voisin de l'Iguanodon..., Bordeaux 1840.
^^a ^bFordyce, R Ewan (June 2018)."Shark-toothed dolphins (Family Squalodontidae)". University of Otago, Department of Geology. Retrieved28 September 2020.
^Braulik, Gill T.; I. Archer, Frederick; Khan, Uzma; Imran, Mohammad; Sinha, Ravindra K.; Jefferson, Thomas A.; Donovan, Carl; Graves, Jeff A. (2021)."Taxonomic revision of the South Asian River dolphins ( Platanista ): Indus and Ganges River dolphins are separate species".Marine Mammal Science.37 (3):1022–1059.Bibcode:2021MMamS..37.1022B.doi:10.1111/mms.12801.hdl:10023/21691.ISSN 0824-0469. Retrieved8 January 2026 – via Wiley Online Library.
^Nobile, F.; Collareta, A.; Perenzin, V.; Fornaciari, E.; Giusberti, L.; Bianucci, G. (2024)."Dawn of the Delphinidans: New Remains ofKentriodon from the Lower Miocene of Italy Shed Light on the Early Radiation of the Most Diverse Extant Cetacean Clade".Biology.13 (2). 114.doi:10.3390/biology13020114.PMC 10887126.PMID 38392334.
^^a ^bMarine Mammal Biology: An Evolutionary Approach By A. Rus Hoelzel. Published 2002 Blackwell Publishing.ISBN 0-632-05232-5
^Whitmore, Jr., F.C., and Sanders, A.E. 1977. Review of the Oligocene Cetacea. Systematic Zoology, 25(4):304–320.
^^a ^bNelson, Margot D.; Lambert, Olivier; Uhen, Mark D. (27 February 2025)."Reassessment of the iconic Oligo‐Miocene heterodont dolphin Squalodon : a redescription of the type species S. grateloupii".Papers in Palaeontology.11 (2).doi:10.1002/spp2.70003.ISSN 2056-2799. Retrieved8 January 2026 – via Wiley Online Library.
^A. C. Dooley. 2003. A review of the eastern North American Squalodontidae (Mammalia: Cetacea). Jeffersoniana 11:1–26
^^a ^bC. Muizon. 1984. Les vertebres fossiles de la Formation Pisco (Perou) II: Les Odontocetes (Cetacea, Mammalia) du Pliocene inferieur de Sud-Sacaco. Institut Francais d'Etudes Andines Editions Recherche sur les Civilizations Memoire 50:1–188
^K. Rothausen. 1968. Die systematische Stellung der europäischen Squalodontidae (Odontoceti, Mamm.). Paläontologische Zeitschrift 42(1–2):83–104
^"†family Kekenodontidae Mitchell 1989".PBDB.

External links

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Odontocete genera

Kingdom:Animalia
Phylum:Chordata
Class:Mammalia
Order:Artiodactyla
Infraorder:Cetacea

Odontoceti

†Agorophius †Ankylorhiza †Archaeodelphis †Argyrocetus †Ashleycetus †Caolodelphis †Chilcacetus †Enigmatocetus †Eoplatanista †Inticetus †Macrodelphinus †Microcetus †Mirocetus †Neosqualodon †Olympicetus †Papahu †Patriocetus †Phoberodon †Phococetus †Prosqualodon †Sachalinocetus †Simocetus †Sulakocetus †Tangaroasaurus
†Xenorophidae	Albertocetus Cotylocara Echovenator Inermorostrum Xenorophus
†Waipatiidae	Awamokoa Ediscetus Nihohae Nihoroa Otekaikea Urkudelphis Waipatia
†Squalodontidae	Eosqualodon Squalodon
†Squaloziphiidae	Crisocetus? Squaloziphius Yaquinacetus
†Eurhinodelphinidae	Ceterhinops Eurhinodelphis Iniopsis Mycteriacetus Phocaenopsis Schizodelphis Vanbreenia Xiphiacetus Ziphiodelphis
Crown-Odontoceti	see below↓

Crown-Odontoceti

Physeteroidea

†Acrophyseter †Albicetus †Brygmophyseter †Eudelphis †Hoplocetus †Livyatan †Miophyseter †Rhaphicetus †Scaldicetus †Zygophyseter
Kogiidae	†Aprixokogia Kogia †Koristocetus †Nanokogia †Platyscaphokogia †Pliokogia †Praekogia †Scaphokogia †Thalassocetus?
Physeteridae	†Aulophyseter †Cozzuoliphyseter †Diaphorocetus †Idiophyseter †Idiorophus †Orycterocetus Physeter †Physeterula †Placoziphius †Thalassocetus?

Platanistoidea

†Aondelphis †Dolgopolis †Ensidelphis †Perditicetus †Eurhinodelphinidae? †Squalodontidae? †Waipatiidae?
†Allodelphinidae?	Allodelphis Arktocara Goedertius Ninjadelphis Zarhinocetus
†Squalodelphinidae?	Furcacetus Huaridelphis Macrosqualodelphis Medocinia Notocetus Phocageneus Squalodelphis
Platanistidae	†Araeodelphis †Dilophodelphis †Grimadelphis †Pachyacanthus? †Pebanista Platanista †Pomatodelphis †Prepomatodelphis †Zarhachis?

Ziphiidae

†Aporotus †Beneziphius †Caviziphius †Chavinziphius †Chimuziphius †Choneziphius †Dagonodum †Globicetus †Imocetus †Messapicetus †Nazcacetus †Nenga †Ninoziphius †Notoziphius †Pterocetus Tasmacetus †Tusciziphius †Xhosacetus †Ziphirostrum
Berardiinae	†Archaeoziphius Berardius †Microberardius
Ziphiinae	†Izikoziphius Ziphius
Hyperoodontinae	†Africanacetus Hyperoodon †Ihlengesi Indopacetus Mesoplodon

Delphinida	see below↓

Delphinida

†Albireo †Atocetus †Brevirostrodelphis †Cammackacetus †Delphinodon †Hadrodelphis †Herbeinodelphis †Liolithax †Lophocetus †Macrokentriodon †Miminiacetus †Odobenocetops †Pictodelphis †Pithanodelphis †Tagicetus †Westmorelandelphis
†Kentriodontidae	Belonodelphis? Kampholophos Kentriodon Platysvercus Sophianacetus Rudicetus Wimahl
Lipotidae	Lipotes †Parapontoporia †Prolipotes

Inioidea

†Awadelphis
Iniidae	†Brujadelphis †Goniodelphis Inia †Ischyrorhynchus †Isoninia? †Isthminia †Kwanzacetus †Meherrinia †Plicodontinia †Saurocetes
Pontoporiidae	†Atocetus? †Auroracetus †Brachydelphis †Piscorhynchus †Pliopontos †Pontistes †Protophocaena †Samaydelphis †Scaldiporia †Stenasodelphis Pontoporia

Delphinoidea

Monodontidae	†Bohaskaia †Casatia Delphinapterus †Denebola †Haborodelphis Monodon
Phocoenidae	†Archaeophocaena †Australithax †Haborophocoena †Lomacetus †Miophocaena Neophocaena †Numataphocoena Phocoena Phocoenoides †Piscolithax †Pterophocaena? †Semirostrum †Septemtriocetus

Delphinidae

†Arimidelphis †Australodelphis †Eodelphinus †Etruridelphis †Hemisyntrachelus Lagenorhynchus Leucopleurus †Norisdelphis Orcinus †Platalearostrum †Pliodelphis †Pterophocaena?
Lissodelphininae	Aethalodelphis Cephalorhynchus Lissodelphis
Delphininae	Delphinus Lagenodelphis Sotalia Sousa Stenella Tursiops
Globicephalinae	Feresa Globicephala Grampus Orcaella Peponocephala Pseudorca Steno

Taxon identifiers
Squalodon	Wikidata:Q774918 Wikispecies:Squalodon BioLib:1118147 EoL:4526484 GBIF:3240248 IRMNG:1052198 Open Tree of Life:4942313 Paleobiology Database:36852

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Description

Fossil record and classification

Species

Species currently recognized as valid

Questionably or originally assigned toSqualodon

See also

References

External links