Hexanchus microdon

Hexanchus microdon; Temporal range: Cenomanian–Danian PreꞒ Ꞓ O S D C P T J K Pg N Possible Aptian to Ypresian record
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Division:	Selachii
Order:	Hexanchiformes
Family:	Hexanchidae
Genus:	Hexanchus
Species:	†H. microdon
Binomial name
	†Hexanchus microdon; (Agassiz, 1835)
Synonyms
	Notidanus microdon Agassiz, 1835;

Hexanchus microdon is an extinct species of sixgill shark that was found worldwide from the mid-Cretaceous to the Paleocene.^[1]^[2]^[3]

Taxonomy

One of the earliest known sixgill sharks in the fossil record, it was described by Louis Agassiz in 1835, but was originally identified by Gideon Mantell in 1822 as a Squalus tooth.^[3] The name has been often applied to any shark teeth from the Late Cretaceous of Europe with a small morphology reminiscent of the modern bigeye sixgill shark, and taxonomic revisions are likely necessary, especially due to the non-informative nature of the type specimens. Teeth from as late as the Early Eocene of Morocco have also been referred to this species, even while concurrent Hexanchus species in other regions are known by different names.^[4]^[5]^[6]^[7] In contrast, at some areas such as the Late Cretaceous of Germany, it appears to be the only Hexanchus species confidently present.^[8] Hexanchus gracilis, a species known from complete fossil skeletons from the Sahel Alma site in Lebanon, may be potentially synonymous with it.^[4]^[6]

Occurrences

Based on the Paleobiology Database:^[1]

Early Cretaceous

?Aptian of Iwate, Japan (Hiraiga Formation)

Late Cretaceous

Europe

Cenomanian of Germany (Hesseltal Formation)^[9]
Cenomanian of England (Cambridge Greensand)^[3]
Cenomanian of Lithuania (Labguva Formation)
Turonian of Germany (Salder Formation)
Coniacian of France (Lezennes Chalk)
Santonian of Germany (Burgsteinfurt Formation)
Campanian of England (upper English Chalk)
Campanian of Belgium (Trivières Chalk)
Campanian of Germany (Beckum Formation)
Maastrichtian of Saratov, Russia (Karsun Formation)^[10]
Maastrchtian of Austria (Gerhartsreit Formation)

North America

Campanian of British Columbia, Canada (Northumberland Formation)^[11]

Asia

Cenomanian of Hokkaido, Japan
Coniacian of Fukushima, Japan (Ashizawa Formation)
Santonian of Kumamoto, Japan (Hinoshima Formation)
Campanian of Ehime, Japan (Izumi Group)
Campanian of Israel (Mishash Formation)
Maastrichtian of Israel (Ghared Formation)

Africa

Coniacian of Angola (Itombe Formation)
Campanian of Angola
Maastrichtian of Egypt
Maastrichtian of Morocco (Ganntour Basin)^[12]

Paleogene

Europe

Danian of Denmark (Rødvig Formation)^[5]

North America

Danian of New Jersey, US (Hornerstown Formation)^[13]
?Thanetian of California, US (Lodo Formation)

References

1 2 "PBDB". paleobiodb.org. Archived from the original on 2022-02-06. Retrieved 2026-08-02.
↑ "Hexanchus microdon | Shark-References". shark-references.com. Retrieved 2026-08-02.
1 2 3 Geology, British Museum (Natural History) Department of; Woodward, Arthur Smith (1889). Catalogue of the Fossil Fishes in the British Museum (Natural History). order of the Trustees.
1 2 Cione, Alberto L.; Reguero, Marcelo (January 1994). "New records of the sharks Isurus and Hexanchus from the Eocene of Seymour Island, Antarctica". Proceedings of the Geologists' Association. 105 (1): 1–14. Bibcode:1994PrGA..105....1C. doi:10.1016/S0016-7878(08)80134-4.
1 2 Adolfssen, Jan; Ward, David (2013). "Neoselachians from the Danian (Early Paleocene) of Denmark". Acta Palaeontologica Polonica. doi:10.4202/app.2012.0123.
1 2 Adolfssen, Jan S.; Ward, David J. (May 2014). "Crossing the boundary: an elasmobranch fauna from S tevns K lint, D enmark". Palaeontology. 57 (3): 591–629. Bibcode:2014Palgy..57..591A. doi:10.1111/pala.12079.
↑ Kanno, Shiori; Tokumaru, Sayaka; Nakagaki, Shuhei; Nakajima, Yasuhisa; Misaki, Akihiro; Hikida, Yoshinori; Sato, Tamaki (May 2022). "Santonian-Campanian neoselachian faunas of the Upper Cretaceous Yezo Group in Nakagawa Town, Hokkaido, Japan". Cretaceous Research. 133 105139. Bibcode:2022CrRes.13305139K. doi:10.1016/j.cretres.2022.105139.
↑ Ladwig, Joachim. "Zu welcher Spezies gehören die Zähne der Gattung Hexanchus (Chondrichthyes, Hexanchiformes) aus der nordwestdeutschen Oberkreide?" (PDF). Arbeitskreis Paläontologie Hannover. 40: 42–56.
↑ Hunt, Adrian P.; Milàn, Jesper; Lucas, Spencer G.; Spielmann, Justin A. (2012). Vertebrate Coprolites: Bulletin 57. New Mexico Museum of Natural History and Science.
↑ Popov, Evgeniy Valerievich; Валериевич, Попов Евгений; Lopyrev, Vladimir Alekseevich; Алексеевич, Лопырев Владимир; Seltzer, Vladimir Borukhovich; Борухович, Сельцер Владимир (2024-12-15). "О находке зуба многожаберной акулы (Neoselachii, Hexanchidae) в верхнем мелу Саратовского Поволжья" [On a record of cow shark’ tooth (Neoselachii, Hexanchidae) from the Upper Cretaceous of Saratov Volga region]. Известия Саратовского Университета. Новая Серия. Серия: Науки О Земле [Izvesiiya of Saratov University. Earth Sciences] (in Russian). 24 (4): 286–293. doi:10.18500/1819-7663-2024-24-4-286-293. Archived from the original on 6 December 2024.
↑ Cappetta, Henri; Morrison, Kurt; Adnet, Sylvain (3 August 2021). "A shark fauna from the Campanian of Hornby Island, British Columbia, Canada: an insight into the diversity of Cretaceous deep-water assemblages". Historical Biology. 33 (8): 1121–1182. Bibcode:2021HBio...33.1121C. doi:10.1080/08912963.2019.1681421.
↑ Cappetta, Henri; Bardet, Nathalie; Pereda Suberbiola, Xabier; Adnet, Sylvain; Akkrim, Driss; Amalik, Mohamed; Benabdallah, Aziza (September 2014). "Marine vertebrate faunas from the Maastrichtian phosphates of Benguérir (Ganntour Basin, Morocco): Biostratigraphy, palaeobiogeography and palaeoecology". Palaeogeography, Palaeoclimatology, Palaeoecology. 409: 217–238. Bibcode:2014PPP...409..217C. doi:10.1016/j.palaeo.2014.04.020.
↑ Case, Gerard R. (19 December 1996). "A new Selachian Fauna from the Lower Hornerstown Formation (Early Paleocene/Montian) of Monmouth County, New Jersey". Palaeontographica Abteilung A. 242 (1–3): 1–14. Bibcode:1996PalAA.242....1C. doi:10.1127/pala/242/1996/1.

[:0-1] 1 2 "PBDB". paleobiodb.org. Archived from the original on 2022-02-06. Retrieved 2026-08-02.

[2] "Hexanchus microdon | Shark-References". shark-references.com. Retrieved 2026-08-02.

[:1-3] 1 2 3 Geology, British Museum (Natural History) Department of; Woodward, Arthur Smith (1889). Catalogue of the Fossil Fishes in the British Museum (Natural History). order of the Trustees.

[:5-4] 1 2 Cione, Alberto L.; Reguero, Marcelo (January 1994). "New records of the sharks Isurus and Hexanchus from the Eocene of Seymour Island, Antarctica". Proceedings of the Geologists' Association. 105 (1): 1–14. Bibcode:1994PrGA..105....1C. doi:10.1016/S0016-7878(08)80134-4.

[:2-5] 1 2 Adolfssen, Jan; Ward, David (2013). "Neoselachians from the Danian (Early Paleocene) of Denmark". Acta Palaeontologica Polonica. doi:10.4202/app.2012.0123.

[:4-6] 1 2 Adolfssen, Jan S.; Ward, David J. (May 2014). "Crossing the boundary: an elasmobranch fauna from S tevns K lint, D enmark". Palaeontology. 57 (3): 591–629. Bibcode:2014Palgy..57..591A. doi:10.1111/pala.12079.

[7] Kanno, Shiori; Tokumaru, Sayaka; Nakagaki, Shuhei; Nakajima, Yasuhisa; Misaki, Akihiro; Hikida, Yoshinori; Sato, Tamaki (May 2022). "Santonian-Campanian neoselachian faunas of the Upper Cretaceous Yezo Group in Nakagawa Town, Hokkaido, Japan". Cretaceous Research. 133 105139. Bibcode:2022CrRes.13305139K. doi:10.1016/j.cretres.2022.105139.

[8] Ladwig, Joachim. "Zu welcher Spezies gehören die Zähne der Gattung Hexanchus (Chondrichthyes, Hexanchiformes) aus der nordwestdeutschen Oberkreide?" (PDF). Arbeitskreis Paläontologie Hannover. 40: 42–56.

[9] Hunt, Adrian P.; Milàn, Jesper; Lucas, Spencer G.; Spielmann, Justin A. (2012). Vertebrate Coprolites: Bulletin 57. New Mexico Museum of Natural History and Science.

[10] Popov, Evgeniy Valerievich; Валериевич, Попов Евгений; Lopyrev, Vladimir Alekseevich; Алексеевич, Лопырев Владимир; Seltzer, Vladimir Borukhovich; Борухович, Сельцер Владимир (2024-12-15). "О находке зуба многожаберной акулы (Neoselachii, Hexanchidae) в верхнем мелу Саратовского Поволжья" [On a record of cow shark’ tooth (Neoselachii, Hexanchidae) from the Upper Cretaceous of Saratov Volga region]. Известия Саратовского Университета. Новая Серия. Серия: Науки О Земле [Izvesiiya of Saratov University. Earth Sciences] (in Russian). 24 (4): 286–293. doi:10.18500/1819-7663-2024-24-4-286-293. Archived from the original on 6 December 2024.

[11] Cappetta, Henri; Morrison, Kurt; Adnet, Sylvain (3 August 2021). "A shark fauna from the Campanian of Hornby Island, British Columbia, Canada: an insight into the diversity of Cretaceous deep-water assemblages". Historical Biology. 33 (8): 1121–1182. Bibcode:2021HBio...33.1121C. doi:10.1080/08912963.2019.1681421.

[12] Cappetta, Henri; Bardet, Nathalie; Pereda Suberbiola, Xabier; Adnet, Sylvain; Akkrim, Driss; Amalik, Mohamed; Benabdallah, Aziza (September 2014). "Marine vertebrate faunas from the Maastrichtian phosphates of Benguérir (Ganntour Basin, Morocco): Biostratigraphy, palaeobiogeography and palaeoecology". Palaeogeography, Palaeoclimatology, Palaeoecology. 409: 217–238. Bibcode:2014PPP...409..217C. doi:10.1016/j.palaeo.2014.04.020.

[:3-13] Case, Gerard R. (19 December 1996). "A new Selachian Fauna from the Lower Hornerstown Formation (Early Paleocene/Montian) of Monmouth County, New Jersey". Palaeontographica Abteilung A. 242 (1–3): 1–14. Bibcode:1996PalAA.242....1C. doi:10.1127/pala/242/1996/1.

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Hexanchus microdon

Taxonomy

Occurrences

Early Cretaceous

Late Cretaceous

Europe

North America

Asia

Africa

Paleogene

Europe

North America

References