Open Paleo

Choyrodon

Gates et al., 2018 kwa-yuh-row-don

Named for the city of Choyr in Mongolia, where the fossils were found, combined with Greek 'odon' meaning 'tooth'.

113.2–100.5 million years ago Albian, Early Cretaceous
Early Cretaceous stages

Choyrodon is a genus of hadrosauroid dinosaur from the Early Cretaceous (Albian) Khuren Dukh Formation of Mongolia. The type and only species is Choyrodon barsboldi. The generic name is derived from the city of Choyr, and -odon, from Latin for tooth; the specific name barsboldi honors paleontologist Rinchen Barsbold. The material consists of a holotype partial skull and cervical ribs, with two other partial skulls both with associated postcranial material. It was found to be the sister taxon of Eolambia.

Under dispute

Choyrodon barsboldi is an early-diverging hadrosauroid whose position within the group is poorly resolved. Gates and colleagues (2018), describing the genus, recovered it as the sister taxon of the North American Eolambia under the Norman (2015) matrix, but under the Wu and Godefroit (2012) matrix it fell into a large unresolved polytomy with other basal hadrosauroids.

Diagnosis

  1. Anterodorsal process of maxilla dorsoventrally broad with length-to-height ratio of 1, dorsal margin reaching and extending along ventral bony naris
  2. Nasal possessing a low rise on dorsal surface positioned at posterior extent of nasal fenestra, with dorsoventrally thickened bone on posterior surface below the dorsal rise
  3. Elongate, hypertrophied external narial fenestra with nasals comprising only a small portion of posteroventral margin
  4. Lacrimal bearing rounded anterior margin and lobate shape in lateral view
  5. Predentary with series of paired foramina below oral margin throughout lateral length of element, and flattened articulation surface across entire ventral margin
  6. Surangular displays two deep osteological folds on lateral surface ventral to second foramen

Species

Choyrodon barsboldi Gates et al., 2018

Type species

Named for Mongolian paleontologist Rinchen Barsbold for contributions to Mongolian paleontology.

Holotype
MPC-D 100/801 , Paleontological Center, Mongolian Academy of Sciences
Material
Partial disarticulated skull with premaxillae, maxilla, ectopterygoid, palatine, pterygoid, jugals, lacrimals, nasal, skull roof, quadratojugals, quadrate, dentaries, predentary, surangulars, angulars, metacarpals, and cervical ribs.
Horizon
lower Khuren Dukh Formation, Albian, Early Cretaceous , 113.2–100.5 million years ago
Locality
Khuren Dukh, Dundgovi, Mongolia

References

  1. Gates, T. A.; Tsogtbaatar, K.; Zanno, L. E.; Chinzorig, T.; Watabe, M. (2018). A new iguanodontian (Dinosauria: Ornithopoda) from the Early Cretaceous of Mongolia. PeerJ 6: e5300. PeerJ. doi:10.7717/peerj.5300

    Erected Choyrodon and recovered it as sister taxon to Eolambia under the Norman (2015) matrix, unresolved under an alternative matrix.

    gates2018a
  2. Paul, G. S. (2024). The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton University Press.

    Source of the appearance features.

    paul2024a
  3. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Classifies Choyrodon as a hadrosauroid of uncertain precise position.

    jones2026a
  4. Norman, D. B. (2015). On the history, osteology, and systematic position of the Wealden (Hastings group) dinosaur Hypselospinus fittoni (Iguanodontia: Styracosterna). Zoological Journal of the Linnean Society 173: 92-189. doi:10.1111/zoj.12193 norman2015a
  5. Wu, W. H.; Godefroit, P. (2012). Anatomy and relationships of Bolong yixianensis, an Early Cretaceous iguanodontoid dinosaur from western Liaoning, China. Bernissart Dinosaurs and Early Cretaceous Terrestrial Ecosystems (Godefroit, P., ed.). Indiana University Press, Bloomington. wu2012a