Claorhynchus

Claorhynchus (meaning "broken beak", as it is based on broken bones from the snout region) is a dubious genus of extinct, ornithischian 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.

History
Paleontologist and naturalist Edward Drinker Cope described what he interpreted as an "agathaumid" (horned dinosaur)'s rostral bone and predentary AMNH 3978, which he said came from the Judith River Formation of Montana, and probably had a horny sheath. It was soon thought to be a hadrosaurid, though. 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.

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 ceratopid's neck frill, probably part of the sqamosal of Triceratops. This information reached Donald F. Glut's series of dinosaur encyclopedias in a confusing, garbled 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. Additionally, other major reviews have left the genus as an indeterminate hadrosaurid.

Thus, there are two views: one that this genus represents a piece of Triceratops frill, and one that it is a dubious hadrosaurid. The photograph of the specimen in Glut's encyclopedia shows a mass of thick polygonal fragments. The provenance data given by Cope suggests an older age than that of Triceratops, but mistakes have been made in the past. At any rate, no modern sources consider its material to permit classification farther than to family, and so it is mostly a historical curiosity at this point.