Claosaurus, meaning “˜broken lizard’, is a genus of hadrosaurid dinosaur from the Late Cretaceous Period (Santonian age). It got its name due to the odd display of its fossils in the bone bed, which appeared to be broken. It was first discovered near the Smokey Hill River in Kansas, USA in 1872. It was originally named Hadrosaurus agilis in 1872, but was changed to Claosaurus agilis in 1890 when major differences between the specimen and Hadrosaurus were discovered. A second species was named in 1892 by O.C. Marsh, but was later reassigned to Anatosaurus and then Edmontosaurus. A third species was named in 1903 by G.R. Wieland.
Claosaurus was slender built with slim feet, long legs, small arms, and a long stiff tail. It was most likely between 12 and 16 feet long and weighed about 1050 pounds. It walked upright on its hind legs, but dropped on all fours to graze. Like other hadrosaurs, it was a herbivorous dinosaur.