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Gyroptychius is an extinct genus of freshwater osteolepiform tetrapodomorphs from the middle to late Devonian period. It is the only known member of the family Gyroptychiidae.[1] They were found throughout much of what is now northern Europe and Greenland, with more dubious records from Canada, Australia & Antarctica.

The following species are known:[1][2]

The following, more dubious species are also known: G.? kiaeri Jarvik, 1949 (Devonian of Norway), G.? taylori Jessen, 1968 (Devonian of Canada), G.? australis Young & Gorter, 1981 (Early Devonian of Australia), and G.? antarcticus (Woodward, 1921) (Famennian-aged Aztec Siltstone of Antarctica). Of these, G.? australis may potentially be referable to the East Asian genus Kenichthys[9], while G. antarcticus is a nomen nudum.[10]

Life restoration of G. agassizi

Gyroptychius was a fast riverine predator with an elongated body about 30 centimetres (12 in) long. As its eyes were relatively small, it is presumed to have hunted by smell rather than sight. Gyroptychius had short jaws which gave it a powerful bite. All its fins except the pectorals were moved to the back to the body, increasing the power of the tail while swimming.[11]

References

  1. ^ a b Borgen, Ulf J.; Nakrem, Hans A. (2016), “Morphology, phylogeny and taxonomy of osteolepiform fish”, Fossils and Strata, Wiley-Blackwell, pp. 1–481, doi:10.1002/9781119286448.ch1, ISBN 978-1-119-28643-1, archived from the original on 2023-02-14, retrieved 2026-04-12{{citation}}: CS1 maint: work parameter with ISBN (link)
  2. ^ “†Gyrolepis M’Coy 1848 (lobe-finned fish)”. The Paleobiology Database.
  3. ^ “Gyroptychius agassizi”. Landscapes of Orkney. Retrieved 2026-04-12.
  4. ^ Newman, Michael (2010-01-01). “Middle Devonian fish from the Orcadian Basin of Scotland. IPC3 pre-conference field trip guide”. IPC3 Pre-conference Field Trip.
  5. ^ Geology, British Museum (Natural History) Department of; Woodward, Arthur Smith (1891). Catalogue of the Fossil Fishes in the British Museum (Natural History): Elasmobranchii (Acanthodii), Holocephali, ichthyodorulites, Ostracodermi, Dipnoi, and Teleostomi (Crossopterygii and chondrostean Actinopterygii). order of the Trustees.
  6. ^ Jarvik, Erik (1985-12-31). “Devonian osteolepiform fishes from East Greenland”. Meddelelser om Grønland. Geoscience. 13: 52 pp.–52 pp. doi:10.7146/moggeosci.v13i.139674. ISSN 1600-4590.
  7. ^ a b Blom, H.; Clack, J.; Ahlberg, P.; Friedman, M. (2007). “Devonian vertebrates from East Greenland: A review of faunal composition and distribution”. Geodiversitas. 29 (1). ISSN 1280-9659.
  8. ^ Newman, Michael J.; Mark-Kurik, Elga; Den Blaauwen, Jan L.; Zupiņš, Ivars (2015). “Scottish Middle Devonian fishes in Estonia”. Scottish Journal of Geology. 51 (2): 141–147. Bibcode:2015ScJG…51..141N. doi:10.1144/sjg2014-006. ISSN 0036-9276.
  9. ^ Young, Gavin Charles; Lu, Jing (2020-04-07). “Asia–Gondwana connections indicated by Devonian fishes from Australia: palaeogeographic considerations”. Journal of Palaeogeography. 9 (1): 8. Bibcode:2020JPalG…9….8Y. doi:10.1186/s42501-020-00057-x. ISSN 2524-4507.
  10. ^ Young, G. C. (1989). “The Aztec fish fauna (Devonian) of Southern Victoria Land: Evolutionary and biogeographic significance”. Geological Society, London, Special Publications. 47 (1): 43–62. Bibcode:1989GSLSP..47…43Y. doi:10.1144/GSL.SP.1989.047.01.05.
  11. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 43. ISBN 1-84028-152-9.