Hadrosaurus is a genus of hadrosaurid ornithopod dinosaurs that lived in North America during the Late Cretaceous Period in what is now the Woodbury Formation about 80 million to 78 million years ago. The holotype specimen was found in fluvial marine sedimentation, meaning that the corpse of the animal was transported by a river and washed out to sea.
They were large animals ranging from 7 to 8 m (23 to 26 ft) and 2 to 4 t (2.2 to 4.4 short tons). Most of the preserved elements are very robust, unusual traits in hadrosaurs. Hadrosaurus were ponderously-built animals equipped with keratinous beaks for cropping foliage and a specialized and complex dentition for food processing.