Myledaphus

Life-forms

Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Classis: Chondrichthyes
Subclassis: Elasmobranchii
Infraclassis: Euselachii
Division/Cohort: Neoselachii
Subdivision/Subcohort: Batoidea
Superordo: Batomorphii
Ordo: Rhinopristiformes

Familia: Rhinobatidae
Genus: †Myledaphus

Species: †M. bipartitus – †M. pustulosus – †M. tritus
Name

†Myledaphus Cope, 1876

Type species: †Myledaphus bipartitus Cope, 1876

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. Reference page.

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
Tooth of Myledaphus bipartitus
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]
Skeleton of M. bipartitus

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.
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).
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. 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.
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.