Claosaurus

Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Megaclassis: Osteichthyes
Cladus: Sarcopterygii
Cladus: Rhipidistia
Cladus: Tetrapodomorpha
Cladus: Eotetrapodiformes
Cladus: Elpistostegalia
Superclassis: Tetrapoda
Cladus: Reptiliomorpha
Cladus: Amniota
Classis: Reptilia
Cladus: Eureptilia
Cladus: Romeriida
Subclassis: Diapsida
Cladus: Sauria
Infraclassis: Archosauromorpha
Cladus: Crurotarsi
Divisio: Archosauria
Cladus: Avemetatarsalia
Cladus: Ornithodira
Subtaxon: Dinosauromorpha
Cladus: Dinosauriformes
Cladus: Dracohors
Cladus: Dinosauria
Ordo: †Ornithischia
Cladus: †Genasauria
Cladus: †Neornithischia
Cladus: †Cerapoda
Subordo: †Ornithopoda
Cladus: †Iguanodontia
Cladus: †Dryomorpha
Cladus: †Ankylopollexia
Superfamilia: †Hadrosauroidea
Genus: Claosaurus
Species (1): C. agilis
Name

Claosaurus Marsh, 1890

References

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: 61–68. Preview

Claosaurus (/ˌkleɪəˈsɔːrəs/ KLAY-ə-SOR-əs; Greek κλάω, klao meaning 'broken' and σαῦρος, sauros meaning 'lizard'; "broken lizard", referring to the odd position of the fossils when discovered) is a genus of hadrosauroid dinosaur that lived during the Late Cretaceous Period (Santonian-Campanian).[2]

Traditionally classified as an early member of the family Hadrosauridae, a 2008 analysis found Claosaurus agilis to be outside of the clade containing Hadrosaurus and other hadrosaurids, making it the closest non-hadrosaurid relative of true hadrosaurids within the clade Hadrosauria.[3]
Description

Because of the insufficient fossil remains ("minority of skull and partial skeleton"), the size of an adult Claosaurus remains uncertain.[4] However, Thomas Holtz gave a length estimate of 3.7 m (12 ft) and a mass estimate as that of a lion.[5] Like other hadrosaurs, it was an herbivore.[3]
History
A Cretoxyrhina and two Squalicorax circling around a dead Claosaurus in the Western Interior Seaway

Evidence of its existence was first found in the Niobrara Formation near the Smoky Hill River in Kansas, United States in the form of partial skull fragments and as an articulated postcranial skeleton. Originally named Hadrosaurus agilis (Marsh, 1872), it was placed in a new genus and renamed Claosaurus agilis in 1890 when major differences between the specimen and Hadrosaurus came to light.[6]

In 1892, Marsh named a second species, C. annectens. It was later reassigned to Anatosaurus and then Edmontosaurus, where it is currently.[7] G. R. Wieland named third species C. affinis in 1903, which he compared to C. annectens. C. affinis was founded on remains from the Pierre Shale of South Dakota, found in association with remains of the giant sea turtle Archelon. At some point after its description, the fragmentary remains were mixed up with the original remains of C. agilis, and a toe bone from C. agilis was accidentally thought to be the only part of the holotype remains that could be located. This was corrected by Joseph Gregory in 1948, who found three toe bones from the right foot of a large hadrosaur in the Yale collections that had comparable preservation to the Pierre Shale turtle remains and were associated with labels in Wieland's handwriting. Gregory found the toe bones to be very similar in size to the corresponding bones of Marsh's Claosaurus annectens, but did not reassign the species due to its much older age and fragmentary remains.[8] C. affinis was considered a dubious hadrosaur in the 2004 review by Jack Horner and colleagues. They reported its type material as lost, although they also reported the remains as only including a single toe bone, instead of the three toe bones described by Gregory.[7]

Reports of gastroliths, or stomach stones, in Claosaurus are actually based on a probable double misidentification. The specimen though to have gastroliths is actually of Edmontosaurus annectens. Barnum Brown, who discovered the specimen in 1900, referred to it as Claosaurus, because E. annectens was thought to be a species of Claosaurus at the time. Additionally, it is more likely that the supposed gastroliths represent gravel washed in during burial.[9]
See also

Dinosaurs portal

Timeline of hadrosaur research

Notes

^ * This species is not accepted as representing Claosaurus in reviews of the genus, but has not been given its own genus and is unlikely to receive one.
References

"Claosaurus agilis".
Doran, Brownstein C. (2021). Dinosaurs from the Santonian–Campanian Atlantic coastline substantiate phylogenetic signatures of vicariance in Cretaceous North America. R. Soc. Open Sci. 8: 210127. https://doi.org/10.1098/rsos.210127
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: 61–68. doi:10.11646/zootaxa.2765.1.6.
Paul, Gregory S. (2010). "Ornithischians". The Princeton Field Guide to Dinosaurs. Princeton: Princeton University Press. pp. 214–316. doi:10.1515/9781400836154.214.
Holtz, Thomas R. Jr. (2012). Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages (PDF). "Winter 2011 Appendix"
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. https://doi.org/10.1080/02724634.1995.10011230
Horner, John R.; Weishampel, David B.; Forster, Catherine A. (2004). "Hadrosauridae". In Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 438–463. ISBN 0-520-24209-2.
Gregory, Joseph T. (1948). "The type of Claosaurus (?) affinis Wieland". American Journal of Science. 246: 29–30. doi:10.2475/ajs.246.1.29.
Creisler, Benjamin S. (2007). "Deciphering duckbills: a history in nomenclature". In Carpenter, Kenneth (ed.). Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs. Bloomington and Indianapolis: Indiana University Press. pp. 185–210. ISBN 978-0-253-34817-3.