Myledaphus

Myledaphus; Temporal range: Turonian-Maastrichtian (possible Paleogene occurrences) PreꞒ Ꞓ O S D C P T J K Pg N
	Myledaphus bipartitus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Order:	Rhinopristiformes
Family:	Rhinobatidae
Genus:	†Myledaphus; Cope, 1876
Type species
	†Myledaphus bipartitus; Cope, 1876
Other species
	†Myledaphus tritus ; Nessov in Nessov & Udovitschenko, 1986; †Myledaphus pustulosus ; Cook, Newbrey, Brinkman, & Kirkland, 2014; †Myledaphus araucanus ; Otero, 2019;

Myledaphus is an extinct genus of guitarfish. It currently contains four valid species found in North America (M. bipartitus, M. pustulosus), South America (M. araucanus), and Central Asia (M. tritus).^[4] It is confirmed to have lived during the Late Cretaceous, with possible occurrences in the Paleocene and early Eocene.^[3]^[5] While the genus is mostly known from teeth, two partial skeletons of M. bipartitus have been found in the Dinosaur Park Formation of Alberta.^[6]

Biology

Close up of *Myledaphus bipartitus* jaws.

Myledaphus remains have been found both in marine and fluvial (freshwater) deposits, suggesting it could tolerate a range of salinity.^[7] In the Hell Creek Formation, composed predominantly of floodplain and riverine deposits, Myledaphus teeth are very common, accounting for a significant fraction of vertebrate remains found in microsites.^[7]

Myledaphus has a durophagus dentition with blunt, polygonal-shaped (hexagonal to rhombic) teeth tessellated into a pavement suited for crushing and grinding hard-bodied prey. Many of their teeth show wear consistent with feeding on mollusks, which were common in the rivers of North America during the Late Cretaceous.^[7]

References

^ Cope, E.D. (1876). "Descriptions of some vertebrate remains from the Fort Union beds of Montana". Proceedings of the Academy of Natural Sciences of Philadelphia. 28: 248–261.
^ Nessov, L.A.; Udovitschenko, N.I. (1986). "Novyye nakhodki ostatkov pozvonochnykh mela i paleogena Sredney Azii [New findings of vertebrate remains from the Cretaceous and Paleogene of Central Asia]". Voprosy Paleontologii. 9: 129–136.
^ ^a ^b Cook, T.D.; Newbrey, M.G.; Brinkman, D.B.; Kirkland, J.I. (2014). "Euselachians from the freshwater deposits of the Hell Creek Formation of Montana". Geological Society of America Special Paper. 503: 229–246. doi:10.1130/2014.2503(08). ISBN 978-0-8137-2503-1.
^ ^a ^b Otero, R.A. (2019). "Myledaphus araucanus sp. nov. (Batomorphi, Rajiformes incertae sedis), a new Late Cretaceous ray from the austral Pacific, and first occurrence of the genus in the Southern Hemisphere". Cretaceous Research. 100: 82–90. Bibcode:2019CrRes.100...82O. doi:10.1016/j.cretres.2019.03.025.
^ Cappetta, H. (2012). Handbook of Paleoichthyology. Volume 3E. Chondrichthyes. Mesozoic and Cenozoic Elasmobranchii: Teeth. Munich: Verlag Dr. Friedrich Pfeil. ISBN 978-3-89937-148-2.
^ Neuman, A.G.; Brinkman, D.B. (2005). "Fishes of the fluvial beds". In Currie, P.J.; Koppelhus, E.B. (eds.). Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed. Bloomington, IN: Indiana University Press. pp. 167–185. ISBN 978-0253345950.
^ ^a ^b ^c Hoffman, Brian L. et al. “Dental Structure of the Late Cretaceous (Maastrichtian) Guitarfish (Neoselachii: Batoidea) Myledaphus pustulosus from the Hell Creek Formation of Garfield County, Montana.” Transactions of the Kansas Academy of Science 121 (2018): 279 - 296.

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[Cope_1876-1] Cope, E.D. (1876). "Descriptions of some vertebrate remains from the Fort Union beds of Montana". Proceedings of the Academy of Natural Sciences of Philadelphia. 28: 248–261.

[Nessov_&_Udovitschenko_1986-2] Nessov, L.A.; Udovitschenko, N.I. (1986). "Novyye nakhodki ostatkov pozvonochnykh mela i paleogena Sredney Azii [New findings of vertebrate remains from the Cretaceous and Paleogene of Central Asia]". Voprosy Paleontologii. 9: 129–136.

[Cook_et_al._2014-3] Cook, T.D.; Newbrey, M.G.; Brinkman, D.B.; Kirkland, J.I. (2014). "Euselachians from the freshwater deposits of the Hell Creek Formation of Montana". Geological Society of America Special Paper. 503: 229–246. doi:10.1130/2014.2503(08). ISBN 978-0-8137-2503-1.

[Otero_2019-4] Otero, R.A. (2019). "Myledaphus araucanus sp. nov. (Batomorphi, Rajiformes incertae sedis), a new Late Cretaceous ray from the austral Pacific, and first occurrence of the genus in the Southern Hemisphere". Cretaceous Research. 100: 82–90. Bibcode:2019CrRes.100...82O. doi:10.1016/j.cretres.2019.03.025.

[Cappetta_2012-5] Cappetta, H. (2012). Handbook of Paleoichthyology. Volume 3E. Chondrichthyes. Mesozoic and Cenozoic Elasmobranchii: Teeth. Munich: Verlag Dr. Friedrich Pfeil. ISBN 978-3-89937-148-2.

[Neuman_&_Brinkman_2005-6] Neuman, A.G.; Brinkman, D.B. (2005). "Fishes of the fluvial beds". In Currie, P.J.; Koppelhus, E.B. (eds.). Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed. Bloomington, IN: Indiana University Press. pp. 167–185. ISBN 978-0253345950.

[:0-7] Hoffman, Brian L. et al. “Dental Structure of the Late Cretaceous (Maastrichtian) Guitarfish (Neoselachii: Batoidea) Myledaphus pustulosus from the Hell Creek Formation of Garfield County, Montana.” Transactions of the Kansas Academy of Science 121 (2018): 279 - 296.

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