Biology:Gyrodus

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Gyrodus (from Greek: γύρος gyros, 'curved' and Greek: ὀδούς odoús 'tooth')[1] is an extinct genus of marine pycnodontiform ray-finned fish that lived from the Middle Jurassic (Bajocian) to the Early Cretaceous (Aptian). It is the only member of the family Gyrodontidae.[2]

With a stratigraphic range from the middle Jurassic to the early-mid Cretaceous, it was one of the longest-surviving and most successful pycnodont genera. It was most abundant in Europe during the Late Jurassic, and was also found off the coast of East Asia and southern regions of the Americas. It saw a precipitous decline in abundance at the start of the Cretaceous, and only a few remains are known from parts of Europe and South America from this period.[3]

Taxonomy

Gyrodus is the only member of the pycnodont family Gyrodontidae, which can be distinguished by certain traits such as a depressed pit in the occlusal surface of the teeth[4], and four dentary teeth.[5] The sister group to this family is thought to be the hypercarnivorous Serrasalmimidae, of which one genus (Polygyrodus) was previously placed in the Gyrodontidae.[6]

The following species are known:[3]

  • †G. circularis Agassiz, 1834 - Late Jurassic (Kimmeridgian to Tithonian) of Germany (Nusplingen Limestone & Solnhofen Formation)
  • †G. hexagonus (de Blainville, 1818) - Middle Jurassic (Oxfordian) of Cuba (Jagua Formation, ssp. cubensis Gregory, 1923), Tithonian of Germany (Solnhofen Formation) (=G. macrophthalmus)
  • †G. huiliches Gouiric-Cavalli, Remírez & Kriwet, 2019 - early Valanginian to early Hauterivian of Neuquen, Argentina[7]
Life restoration of G. hexagonus

In the past, many other species were known, but almost all were synonymized with G. circularis and G. hexagonus.[8] The earliest definite record of Gyrodus is from the Middle Jurassic (Bajocian) of Scotland, which was initially assigned to the species G. goweri, but is likely too fragmentary for a species description. They become much more common during the Late Jurassic, and fossils of Gyrodus are common throughout Europe, including France (including the Cerin Lagerstatte), Germany, Switzerland (Reuchenette Formation), Italy, and Spain. From the Americas, it is known from the Late Jurassic of Chile and the Kimmeridgian of Mexico. In Asia, it is known from the Tithonian of Japan and Siberia.[3]

During the Early Cretaceous, indeterminate Gyrodus remains are known from the Barremian & Hauterivian of Germany, with the final known record of Gyrodus being remains assigned to the species "G. minor" from the Aptian of England.[3]

Palaeobiology

Dental microwear indicates that Gyrodus planidens closed its jaw in a propalinal motion with the prearticular shearing against the vomer during the powerstroke rather than through purely vertical jaw movement.[9]

References

  1. ↑ Roberts, George (1839) (in English). An etymological and explanatory dictionary of the terms and language of geology. London: Longman, Orme, Brown, Green, & Longmans. p. 74. https://archive.org/details/anetymologicala00robegoog. Retrieved 30 December 2021. 
  2. ↑ Ebert, Martin (2019-10-21). "A new genus of Pycnodontidae (Actinopterygii) from the Upper Jurassic of France and Germany, included in a phylogeny of Pycnodontiformes" (in en). Zoological Journal of the Linnean Society. doi:10.1093/zoolinnean/zlz087. ISSN 0024-4082. https://academic.oup.com/zoolinnean/advance-article/doi/10.1093/zoolinnean/zlz087/5601911. 
  3. ↑ 3.0 3.1 3.2 3.3 Kriwet, Jürgen; Schmitz, Lars (2005). "New insight into the distribution and palaeobiology of the pycnodont fish Gyrodus". Acta Palaeontologica Polonica 50 (1): 49–56. https://www.app.pan.pl/article/item/app50-049.html. 
  4. ↑ Cawley, John J.; Kriwet, Jürgen (2024-04-09). "The Fossil Record and Diversity of Pycnodontiform Fishes in Non-Marine Environments" (in en). Diversity 16 (4): 225. doi:10.3390/d16040225. ISSN 1424-2818. Bibcode: 2024Diver..16..225C. 
  5. ↑ Ebert, Martin (2019-10-21). "A new genus of Pycnodontidae (Actinopterygii) from the Upper Jurassic of France and Germany, included in a phylogeny of Pycnodontiformes" (in en). Zoological Journal of the Linnean Society. doi:10.1093/zoolinnean/zlz087. ISSN 0024-4082. https://academic.oup.com/zoolinnean/advance-article/doi/10.1093/zoolinnean/zlz087/5601911. 
  6. ↑ Vullo, Romain; Cavin, Lionel; Khalloufi, Bouziane; Amaghzaz, Mbarek; Bardet, Nathalie; Jalil, Nour-Eddine; Jourani, Essaid; Khaldoune, Fatima et al. (2017-07-28). "A unique Cretaceous–Paleogene lineage of piranha-jawed pycnodont fishes" (in en). Scientific Reports 7 (1): 6802. doi:10.1038/s41598-017-06792-x. ISSN 2045-2322. PMID 28754956. Bibcode: 2017NatSR...7.6802V. 
  7. ↑ Gouiric-Cavalli, Soledad; Remírez, Mariano; Kriwet, Jürgen (2019-02-01). "New pycnodontiform fishes (Actinopterygii, Neopterygii) from the Early Cretaceous of the Argentinian Patagonia". Cretaceous Research 94: 45–58. doi:10.1016/j.cretres.2018.10.003. ISSN 0195-6671. PMID 30996506. Bibcode: 2019CrRes..94...45G. 
  8. ↑ Lambers, Paul H. (1991-12-16). "The Upper Jurassic actinopterygian fish Gyrodus dichactinius Winkler 1862 (Gyrodus hexagonus [Blainville 1818) from Solnhofen, Bavaria and anatomy of the genus Gyrodus Agassiz"] (in en). Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen 94 (4): 489–544. http://hdl.handle.net/1874/420977. 
  9. ↑ Baines, David Christian (31 October 2010). Tooth Microwear in Fishes (PhD thesis). University of Leicester. Retrieved 18 March 2026.

Further reading

  • Fossils (Smithsonian Handbooks) by David Ward

Template:Pycnodontiformes Wikidata ☰ Q1092164 entry



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