Claosaurus
| Claosaurus Temporal range: Late Cretaceous,  | |
|---|---|
| Type specimen in the Peabody Museum, with restored skull | |
| Scientific classification | |
| Domain: | Eukaryota | 
| Kingdom: | Animalia | 
| Phylum: | Chordata | 
| Clade: | Dinosauria | 
| Clade: | †Ornithischia | 
| Clade: | †Ornithopoda | 
| Clade: | †Hadrosauromorpha | 
| Genus: | †Claosaurus Marsh, 1890 | 
| Type species | |
| †Hadrosaurus agilis (Marsh, 1872a) Marsh, 1890 | |
| Synonyms | |
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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).
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 Hadrosauromorpha.