Myledaphus

Myledaphus
Temporal range: Turonian-Maastrichtian (possible Paleogene occurrences)
Myledaphus bipartitus
Scientific classification Edit this classification
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 contains four valid species found in North America (M. bipartitus, M. pustulosus), South America (M. araucanus), and Central Asia (M. tritus). It is confirmed to have lived during the Late Cretaceous, with possible occurrences in the Paleocene and early Eocene. While the genus is mostly known from teeth, two partial skeletons of M. bipartitus have been found in the Dinosaur Park Formation of Alberta.

Biology

Life restoration of M. bipartitus

Myledaphus remains have been found both in marine and fluvial (freshwater) deposits, suggesting it could tolerate a range of salinity. This genus was able to move into the North American continent due to an intercontinental seaway flood that happened later on in the cretaceous period. 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.

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. Their tooth shape are commonnly described as ray teeth. Many of their teeth show wear consistent with feeding on mollusks, which were common in the rivers of North America during the Late Cretaceous.

Myledaphus also have other traits aside from their teeth that can help identify them. Many of their fossils exhibit very similar shapes such as having "large pectoral fins that do not expand anterior to the eyes" but actually they serve to " form an angular disk that expands caudually".

References

  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.
  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.
  3. 1 2 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.{{cite journal}}: CS1 maint: periodical has ISBN (link)
  4. 1 2 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.
  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.
  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.
  7. 1 2 3 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.
  8. ↑ Gates, Terry A.; Gorscak, Eric; Makovicky, Peter J. (2019-01-22). "New sharks and other chondrichthyans from the latest Maastrichtian (Late Cretaceous) of North America". Journal of Paleontology. 93 (3): 512–530. doi:10.1017/jpa.2018.92. ISSN 0022-3360.
  9. ↑ Otero, Rodrigo A. (August 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. ISSN 0195-6671.
  10. ↑ Wilson, Alycia E.; Newbrey, Michael G.; Brinkman, Donald B.; Cook, Todd D.; Neuman, Andrew G. (September 2013). "Age and growth in Myledaphus bipartitus, a Late Cretaceous freshwater guitarfish from Alberta, Canada". Canadian Journal of Earth Sciences. 50 (9): 930–944. doi:10.1139/cjes-2013-0001. ISSN 0008-4077.