Claorhynchus

The holotype specimen, AMNH 3978, was described by American paleontologist Edward Drinker Cope in 1892, who interpreted it as the rostral bone and predentary of a member of Agathaumidae from the Laramie Formation of Colorado.^[1] It was reinterpreted as a hadrosaurid, though, by American paleontologist John Bell Hatcher in 1902 and removed as a ceratopsid.^[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]