Ischyodus

Ischyodus; Temporal range: 176–23 Ma PreꞒ Ꞓ O S D C P T J K Pg N Middle Jurassic to Miocene
	Nearly complete specimen of Ischyodus quenstedti from the Solnhofen Limestone
	Life restoration of Ischyodus quenstedti (sometimes considered a synonym of I. egertoni)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Holocephali
Order:	Chimaeriformes
Family:	Callorhinchidae
Genus:	†Ischyodus; Egerton, 1843
Species
	Ischyodus bifurcatus; Ischyodus brevirostris; Ischyodus dolloi; Ischyodus gubkini; Ischyodus incisus; Ischyodus latus; Ischyodus lonzeensis; Ischyodus minor; Ischyodus mortoni; Ischyodus planus; Ischyodus rayhaasi; Ischyodus thurmanni; Ischyodus townsendi; Ischyodus williamsae; Ischyodus yanshini; Ischyodus zinsmeisteri;

Ischyodus (from Greek: ισχύς ischýs, 'power' and Greek: ὀδούς odoús 'tooth') is an extinct genus of chimaera. It is the most diverse and long-lived chimaera genus, with over 39 species found worldwide spanning over 140 million years from the Middle Jurassic to the Miocene.^[1] Almost all species are only known from tooth plates, with the exception of the Jurassic species I. quenstedti.^[2] Complete specimens of I. quenstedti from the Late Jurassic of Germany most closely resemble the genus Callorhinchus amongst living chimaera genera.^[3] It is sometimes placed in the "Edaphodontidae", a unclearly defined group of chimaera with an uncertain position within the clade,^[1] while other authors place it into Callorhinchidae along with Callorhinchus,^[4] a position that has been supported by at least some phylogenetic analyses.^[5] It is suggested therefore to probably have had a similar ecology to living Callorhinchus.^[2]

Based on complete specimens from the Solnhofen Limestone of Germany, the total length is assumed to be 21 times larger than mesiodistal length of mandibular tooth plate. For example, I. bifurcatus with mandibular plate length of 3.2 in (8.2 cm) possibly belongs 5 ft 8 in (1.72 m) long specimen.^[6] The front of the head of I. quenstedti has an elongate tapering snout, with the body having a long, unornamented dorsal fin spine, as well as a heterocercal tail fin.^[2]

References

^ ^a ^b Johnson-Ransom, Evan D.; Popov, Evgeny V.; Deméré, Thomas A.; Shimada, Kenshu (October 2018). "The Late Cretaceous Chimaeroid Fish, Ischyodus bifurcatus Case (Chondrichthyes: Holocephali), from California, USA, and Its Paleobiogeographical Significance". Paleontological Research. 22 (4): 364–372. doi:10.2517/2018PR004. ISSN 1342-8144. S2CID 133941390.
^ ^a ^b ^c Villalobos-Segura, Eduardo; Stumpf, Sebastian; Türtscher, Julia; Jambura, Patrick L.; Begat, Arnaud; López-Romero, Faviel A.; Fischer, Jan; Kriwet, Jürgen (March 2023). "A Synoptic Review of the Cartilaginous Fishes (Chondrichthyes: Holocephali, Elasmobranchii) from the Upper Jurassic Konservat-Lagerstätten of Southern Germany: Taxonomy, Diversity, and Faunal Relationships". Diversity. 15 (3): 386. doi:10.3390/d15030386. ISSN 1424-2818. PMC 7614348. PMID 36950327.
^ Popov, E. V., Duffin, C. J., Tischlinger, H. and Atuchin, A., 2013: Reconstructions of the German Plattenkalk (Late Jurassic) chimaeroid fishes (Holocephali, Chimaeroidei). In, Schwarz, C. and Kriwet, J. eds., Sixth International Meeting on Mesozoic Fishes: Diversification and Diversity Patterns. Abstracts, p. 56. Verlag Friedrich Pfeil, Munich
^ Otero, Rodrigo; Figueroa Bravo, Constanza; Soto Huenchuman, Paula; Fernández-Collemann, Sara; Valenzuela Toro, Ana; Gutstein, Carolina (2021). "First record of Ischyodus (Chondrichthyes, Holocephali) from the Upper Jurassic of southwestern Gondwana". Acta Palaeontologica Polonica. 66. doi:10.4202/app.00859.2020. ISSN 0567-7920.
^ Brownstein, Chase D.; Near, Thomas J.; Dearden, Richard P. (October 2024). "The Palaeozoic assembly of the holocephalan body plan far preceded post-Cretaceous radiations into the ocean depths". Proceedings of the Royal Society B: Biological Sciences. 291 (2033). doi:10.1098/rspb.2024.1824. ISSN 0962-8452. PMC 11521621. PMID 39471859.
^ Johnson-Ransom, Evan D.; Popov, Evgeny V.; Deméré, Thomas A.; Shimada, Kenshu (2018-10-01). "The Late Cretaceous Chimaeroid Fish, Ischyodus bifurcatus Case (Chondrichthyes: Holocephali), from California, USA, and Its Paleobiogeographical Significance". Paleontological Research. 22 (4): 364–372. doi:10.2517/2018PR004. ISSN 1342-8144. S2CID 133941390.

External links

Image of a ratfish, Ischyodus rayhaasi, mandible

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[:0-1] Johnson-Ransom, Evan D.; Popov, Evgeny V.; Deméré, Thomas A.; Shimada, Kenshu (October 2018). "The Late Cretaceous Chimaeroid Fish, Ischyodus bifurcatus Case (Chondrichthyes: Holocephali), from California, USA, and Its Paleobiogeographical Significance". Paleontological Research. 22 (4): 364–372. doi:10.2517/2018PR004. ISSN 1342-8144. S2CID 133941390.

[:2-2] Villalobos-Segura, Eduardo; Stumpf, Sebastian; Türtscher, Julia; Jambura, Patrick L.; Begat, Arnaud; López-Romero, Faviel A.; Fischer, Jan; Kriwet, Jürgen (March 2023). "A Synoptic Review of the Cartilaginous Fishes (Chondrichthyes: Holocephali, Elasmobranchii) from the Upper Jurassic Konservat-Lagerstätten of Southern Germany: Taxonomy, Diversity, and Faunal Relationships". Diversity. 15 (3): 386. doi:10.3390/d15030386. ISSN 1424-2818. PMC 7614348. PMID 36950327.

[3] Popov, E. V., Duffin, C. J., Tischlinger, H. and Atuchin, A., 2013: Reconstructions of the German Plattenkalk (Late Jurassic) chimaeroid fishes (Holocephali, Chimaeroidei). In, Schwarz, C. and Kriwet, J. eds., Sixth International Meeting on Mesozoic Fishes: Diversification and Diversity Patterns. Abstracts, p. 56. Verlag Friedrich Pfeil, Munich

[4] Otero, Rodrigo; Figueroa Bravo, Constanza; Soto Huenchuman, Paula; Fernández-Collemann, Sara; Valenzuela Toro, Ana; Gutstein, Carolina (2021). "First record of Ischyodus (Chondrichthyes, Holocephali) from the Upper Jurassic of southwestern Gondwana". Acta Palaeontologica Polonica. 66. doi:10.4202/app.00859.2020. ISSN 0567-7920.

[:1-5] Brownstein, Chase D.; Near, Thomas J.; Dearden, Richard P. (October 2024). "The Palaeozoic assembly of the holocephalan body plan far preceded post-Cretaceous radiations into the ocean depths". Proceedings of the Royal Society B: Biological Sciences. 291 (2033). doi:10.1098/rspb.2024.1824. ISSN 0962-8452. PMC 11521621. PMID 39471859.

[6] Johnson-Ransom, Evan D.; Popov, Evgeny V.; Deméré, Thomas A.; Shimada, Kenshu (2018-10-01). "The Late Cretaceous Chimaeroid Fish, Ischyodus bifurcatus Case (Chondrichthyes: Holocephali), from California, USA, and Its Paleobiogeographical Significance". Paleontological Research. 22 (4): 364–372. doi:10.2517/2018PR004. ISSN 1342-8144. S2CID 133941390.

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