Claosaurus
From Greek klao (κλάω) meaning 'broken' and Greek sauros (σαῦρος) meaning 'lizard'. Full meaning: 'broken lizard', referring to the unusual position of the fossils when discovered.
Claosaurus is a genus of hadrosauroid dinosaur that lived during the Late Cretaceous Period (Santonian-Campanian) of what is now North America. The type and only known valid species is Claosaurus agilis. Traditionally classified as an early member of the family Hadrosauridae, a 2008 analysis found Claosaurus to be outside of the clade containing Hadrosaurus and other hadrosaurids, making it the closest non-hadrosaurid relative of true hadrosaurids within the clade Hadrosauromorpha.
Under dispute
Claosaurus agilis has been called a basal hadrosaurid (Carpenter and colleagues, 1995), but later work consistently places it outside Hadrosauridae, among the non-hadrosaurid hadrosauromorphs (Prieto-Márquez, 2011; Tsogtbaatar and colleagues, 2019).
Diagnosis
- Only a single row of teeth in use at one time (unlike Hadrosaurus-type multiple rows)
- Cervical vertebrae very short and strongly opisthocolian
- Fore limbs very small
- Seven vertebrae in the sacrum, firmly coossified
- Caudal vertebrae longer than wide, tail quite elongate
- Ilium intermediate in form between Hadrosaurus and Stegosaurus, with very slender and elongate portion in front of acetabulum
Species
Claosaurus agilis Marsh, 1890
Type species
From Latin 'agilis' meaning 'agile', referring to the inferred agility of this hadrosauroid dinosaur.
- Holotype
- YPM 1190 , Yale Peabody Museum of Natural History
- Material
- Partial skeleton including vertebrae, ilium, fibula, astragalus, metatarsals, and phalanges.
- Horizon
- Smoky Hill Chalk Member, Niobrara Chalk Formation, Coniacian–Campanian, Late Cretaceous , 89.8–72.2 million years ago
- Locality
- Smoky Hill River, Kansas, United States Carpenter and colleagues (1995) date the Smoky Hill Chalk along the Smoky Hill River in Logan County "near the Santonian–Campanian boundary"; Prieto-Márquez (2011) gives the holotype's beds as late Coniacian.
References
-
Carpenter, K.; Dilkes, D.; Weishampel, D. B. (1995). The Dinosaurs of the Niobrara Chalk Formation (Upper Cretaceous, Kansas). Journal of Vertebrate Paleontology 15(2): 275-297. Informa UK Limited. doi:10.1080/02724634.1995.10011230
Gives the holotype as collected on the north side of the Smoky Hill River, 26 miles east of Fort Wallace, in the Smoky Hill Chalk Member.
carpenter1995a -
Prieto-Márquez, A. (2011). Revised diagnoses of Hadrosaurus foulkii Leidy, 1858 (the type genus and species of Hadrosauridae Cope, 1869) and Claosaurus agilis Marsh, 1872 (Dinosauria: Ornithopoda) from the Late Cretaceous of North America. Zootaxa 2765(1): 61-68. Magnolia Press. doi:10.11646/zootaxa.2765.1.6
Gives the holotype's beds as "Late Coniacian in age according to Everhart and Ewell (2006)".
prieto-márquez2011b - Marsh, O. C. (1890). Additional characters of the Ceratopsidae, with notice of new Cretaceous dinosaurs. American Journal of Science s3-39(233): 418-426. American Journal of Science (AJS). doi:10.2475/ajs.s3-39.233.418 marsh1890a
-
Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.
Source of the body length, mass, and hip height estimates.
jones2026a -
Tsogtbaatar, K.; Weishampel, D. B.; Evans, D. C.; Watabe, M. (2019). A new hadrosauroid (Dinosauria: Ornithopoda) from the Late Cretaceous Baynshire Formation of the Gobi Desert (Mongolia). PLOS ONE 14(4): e0208480. Public Library of Science (PLoS). doi:10.1371/journal.pone.0208480
New hadrosauroid description's phylogeny placed Claosaurus among derived hadrosauromorphs outside Hadrosauridae.
tsogtbaatar2019a -
Everhart, M. J.; Ewell, K. (2006). Shark-bitten dinosaur (Hadrosauridae) caudal vertebrae from the Niobrara Chalk (Upper Coniacian) of western Kansas. Transactions of the Kansas Academy of Science 109: 27-35. doi:10.1660/0022-8443(2006)109[27:sdhcvf]2.0.co;2
Cited by Prieto-Márquez (2011) for the Late Coniacian age of the holotype's beds.
everhart2006a