Open Paleo

Claorhynchus

Cope, 1892 Nomen dubium

From Greek 'klao' ('to break') and 'rhynchos' ('beak'), for the broken condition of the beak bones on which the genus was founded.

Claorhynchus 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.

Under dispute

Which group the type specimen belongs to is unresolved. Cope (1892) founded the genus on what Cope took to be a rostral and predentary of a ceratopsian, referring it to the Agathaumidae. Hatcher (1907) removed it from the Ceratopsia on the strength of Cope's description alone, supposing it to be a trachodontid, and Lull and Wright (1942) read the material as a hadrosaur premaxilla and dentary, a placement followed by White (1973), Horner and colleagues (2004) and Jones (2026). Against that, Brett-Surman (1989) relocated the type in the collections and examined it, concluding that it is part of a ceratopsian frill, probably the lateral edge of a Triceratops squamosal, and that it is certainly not a hadrosaurid. Because that re-examination has not been answered, the genus is placed at Ornithischia incertae sedis, the least inclusive clade common to both readings. Every treatment cited for this taxon agrees the specimen is too incomplete to diagnose.

Species

Claorhynchus trihedrus Cope, 1892 Nomen dubium

Type species

Holotype
AMNH 3978 , American Museum of Natural History
Material
Beak-region bones found together with fragments of a massive supratemporal bone, described by Cope as a rostral and predentary.
Notes
What the specimen actually is has been read three ways. Cope (1892) described a ceratopsian rostral and predentary, Lull and Wright (1942) a hadrosaur premaxilla and dentary, and Brett-Surman (1989), who relocated the specimen and examined it, part of a ceratopsian frill.
Horizon
Late Cretaceous
Locality
United States Cope gives no locality and no horizon beyond "the Laramie", and Hatcher (1902) records the type as "locality and horizon not given". Lull and Wright (1942) give a hedged "?Judith River" in Montana, which later work repeats while dropping their question mark and adding a county that none of them sources.

References

  1. Cope, E. D. (1892). Fourth note on the Dinosauria of the Laramie. The American Naturalist 26(310): 756-758. University of Chicago Press. doi:10.1086/275585

    Erects the genus on beak bones found with fragments of a supratemporal, referring it to the ceratopsian family Agathaumidae.

    cope1892a
  2. Hatcher, J. B. (1902). The genera and species of the Trachodontidae (Hadrosauridae, Claosauridae) Marsh. Annals of the Carnegie Museum 1(3): 377-386. doi:10.5962/p.331063

    Records the type's "locality and horizon not given", and supposes from Cope's description that it is a trachodontid.

    hatcher1902a
  3. Lull, R. S.; Wright, N. E. (1942). Hadrosaurian Dinosaurs of North America. Geological Society of America Special Papers 40: 1-272. Geological Society of America. doi:10.1130/spe40-p1

    Gives the provenance as "?Judith River", Montana, with the query.

    lull1942a
  4. Hatcher, J. B.; Marsh, O. C.; Lull, R. S. (1907). The Ceratopsia. Monographs of the United States Geological Survey 49: 1-300. United States Geological Survey.

    Removes the genus from the Ceratopsia, supposing from Cope's description that it belongs with the trachodontids, and gives the type as AMNH 3978.

    hatcher1907a
  5. White, T. E. (1973). Catalogue of the genera of dinosaurs. Annals of Carnegie Museum 44: 117-155. doi:10.5962/p.243870

    Records the type as a premaxillary tip and predentary and assigns the genus to Hadrosauridae, with a Judith River Formation provenance in Fergus County, Montana.

    white1973a
  6. Brett-Surman, M. K. (1989). A revision of the Hadrosauridae (Reptilia: Ornithischia) and their evolution during the Campanian and Maastrichtian. 1-272. Doctoral thesis, The George Washington University.

    Relocated and examined the type, identifying it as part of a ceratopsian frill and rejecting the hadrosaur reading.

    brett-surman1989a
  7. Olshevsky, G. (1991). A revision of the parainfraclass Archosauria Cope, 1869, excluding the advanced Crocodylia. Mesozoic Meanderings 2: 1-196.

    Lists the genus as a nomen dubium under Triceratops.

    olshevsky1991a
  8. Horner, J. R.; Weishampel, D. B.; Forster, C. A. (2004). Hadrosauridae. The Dinosauria, Second Edition (Weishampel, D. B.; Dodson, P.; Osmólska, H., eds.) 438-463. University of California Press, Berkeley.

    Lists the species among hadrosaurid nomina dubia, with the material given as fragmentary premaxillae and predentary.

    horner2004a
  9. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Records that the genus has been considered both hadrosaurid and ceratopsid, and treats it as an indeterminate hadrosaurid.

    jones2026a