An American herbivorous dinosaur of great size, allied to the iguanodon. It is found in the Cretaceous formation.

any of numerous large bipedal ornithischian dinosaurs having a horny duck-like bill and webbed feet; may have been partly aquatic

(pronounced HAD-roh-SAWR-us) Hadrosaurus ( meaning "bulky lizard" ) was a duck-billed dinosaur, a 23 to 32 feet (7 to 10 m) long ornithischian from the late Cretaceous period. Hadrosaurus was discovered by W. P. Foulke and excavated and named by anatomist J. Leidy in 1858 from a skull-less skeleton and hundreds of teeth found in New Jersey. It was the first American dinosaur to be described and the first nearly-complete dinosaur skeleton. Although the Hadrosaurids are named for this genus, Hadrosaurus is a doubtful genus because there is so little fossil information about it (including no skull). The type species is H. foulkii; it was named by paleontologist J. Leidy in 1858.