Gryposaurus (meaning "hooked-nosed (Greek grypos) lizard"; sometimes incorrectly translated as "griffin (Latin gryphus) lizard") was a genus of duckbilled dinosaur that lived about 83 to 74 million years ago, in the Late Cretaceous (late Santonian to late Campanian stages) of North America. Named species of Gryposaurus are known from the Dinosaur Park Formation in Alberta, Canada, and two formations in the United States: the Lower Two Medicine Formation in Montana and the Kaiparowits Formation of Utah.
Gryposaurus is similar to Kritosaurus, and for many years the two were thought to be synonyms. It is known from numerous skulls, some skeletons, and even some skin impressions that show it to have had pyramidal scales projecting along the midline of the back. It is most easily distinguished from other duckbills by its narrow arching nasal hump, sometimes described as similar to a "Roman nose," and which may have been used for species or sexual identification, and/or combat with individuals of the same species. A large bipedal/quadrupedal herbivore around 9 meters long (30 ft), it may have preferred river settings.
Gryposaurus was a hadrosaurid of typical size and shape; one of the best specimens of this genus, the nearly complete type specimen of Kritosaurus incurvimanus (now regarded as a synonym of Gryposaurus notabilis) came from an animal about 8.2 meters long (27 feet). This specimen also has the best example of skin impressions for Gryposaurus, showing this dinosaur to have had several different types of scalation: pyramidal, ridged, limpet-shaped scutes upwards of 3.8 centimeters long (1.5 inches) on the flank and tail; uniform polygonal scales on the neck and sides of the body; and pyramidal structures, flattened side-to-side, with fluted sides, longer than tall and found along the top of the back in a single midline row.
The three named species of Gryposaurus differ in details of the skull and lower jaw. The prominent nasal arch found in this genus is formed from the paired nasal bones. In profile view, they rise into a rounded hump in front of the eyes, reaching a height as tall as the highest point of the back of the skull. The skeleton is known in great detail, making it a useful point of reference for other duckbill skeletons.