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Temporal range: Late Cretaceous
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Clade: Genasauria
Clade: Neornithischia
Clade: Cerapoda
Genus: Claorhynchus
Cope, 1892
C. trihedrus
Binomial name
Claorhynchus trihedrus
Cope, 1892

Claorhynchus (meaning "broken beak", as it is based on broken bones from the snout region) is a dubious genus of cerapodan dinosaur with a confusing history behind it. It has been considered to be both a hadrosaurid and a ceratopsid, sometimes the same as Triceratops, with two different assignments as to discovery formation and location, and what bones make up its type remains.


The holotype specimen, AMNH 3978, was described by paleontologist and naturalist Edward Drinker Cope, who interpreted it as the rostral bone and predentary of an "agathaumid" (ceratopsid) dinosaur, which he said came from the Laramie Formation of Colorado.[1] It was soon thought to be a hadrosaurid, though.[2][3] In 1904, Franz Baron Nopcsa reclassified it as a ceratopsid.[4] In their influential monograph, Richard Swann Lull and Nelda E. Wright regarded the genus as a dubious type of hadrosaurid, based on premaxillae and a predentary.[5]

This opinion stood until the work of Michael K. Brett-Surman, who stated in his dissertation that, having rediscovered and reexamined the material with Douglas A. Lawson, it was most likely part of a ceratopsid's neck frill, probably part of the squamosal of Triceratops.[6] This information reached Donald F. Glut's series of dinosaur encyclopedias in a confusing form; its entry states that a squamosal and tooth from South Dakota were referred to the genus, and these are what Brett-Surman and Lawson identified, keeping the supposed beak remains separate.[7] Additionally, other major reviews have left the genus as an indeterminate hadrosaurid.[8][9]


  1. ^ Cope, E.D. (1892). Fourth note on the Dinosauria of the Laramie. The American Naturalist 26:756-758.
  2. ^ Hatcher, J.B. (1902). The genus and species of the Trachodontidae (Hadrosauridae, Claosauridae) Marsh. Annals of the Carnegie Museum 14(1):377-386.
  3. ^ Hatcher, J.B., Marsh, O.C., and Lull, R.S. (1907). The Ceratopsia. Government Printing Office:Washington, D.C., 300 pp. ISBN 0-405-12713-8
  4. ^ Nopcsa, F (1904). "Dinosaurierreste aus Siebenbürgen III (Weitere Schädelreste von Mochlodon)". Denkschriften der Mathematisch-Naturwissenschaftlichen Classe der Kaiserlichen Akademie der Wissenschaften. LXXIV: 229–263.
  5. ^ Lull, R.S., and Wright, N.E. (1942). Hadrosaurian Dinosaurs of North America. Geological Society of America Special Paper 40:1-242.
  6. ^ Brett-Surman, M.K. 1989(1988). A revision of the Hadrosauridae (Reptilia: Ornithischia) and their evolution during the Campanian and Maastrichtian. Ph.D. dissertation, George Washington University:Washington, D.C.. pp.1-272.
  7. ^ Glut, D.F. (1997). "Claorhynchus". Dinosaurs: The Encyclopedia. McFarland & Company. p. 299. ISBN 978-0-89950-917-4.
  8. ^ Weishampel, D.B., and Horner, J.R. (1990). Hadrosauridae. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). The Dinosauria. University of California Press:Berkeley, 534-561. ISBN 0-520-24209-2
  9. ^ Horner, J.R., Weishampel, D.B., and Forster, C.A. (2004). Hadrosauridae. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). The Dinosauria (second edition). University of California Press:Berkeley, 438-463. ISBN 0-520-06727-4.