Gryposaurus

Gryposaurus (meaning "hooked-nosed (Greek grypos) lizard";[1] sometimes incorrectly translated as "griffin (Latin gryphus) lizard"[2]) was a genus of duckbilled dinosaur that lived about 83 to 75.5 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 the Lower Two Medicine Formation in Montana and the Kaiparowits Formation of Utah in the United States.

Gryposaurus is similar to Kritosaurus, and for many years was regarded as the same genus. It is known from numerous skulls, some skeletons, and even some skin impressions that show it to have had pyramidal scales pointing out 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,"[1] 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.

Description
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).[3] 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.[4]

The three named species of Gryposaurus differ in details of the skull and lower jaw.[2] 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.[5] The skeleton is known in great detail,[6] making it a useful point of reference for other duckbill skeletons.

Classification
Gryposaurus was a hadrosaurine hadrosaurid, a member of the duckbill subfamily without hollow head crests.[7] The general term "gryposaur" is sometimes used for duckbills with arched nasals.[8] Tethyshadros was once thought to fall into this group as well, before it was described (then known under the nickname "Antonio").[9] A subfamily, Gryposaurinae, was coined by Jack Horner for it as part of a larger revision that promoted Hadrosaurinae to family status,[10] but is not in use. The issue of its relationships to other hadrosaurs is equivocal anyway due to the lack of resolution on how it compares to Kritosaurus. At this time, the main differences between the two are location (Alberta and Montana for Gryposaurus, New Mexico for Kritosaurus) and age (Kritosaurus comes from slightly younger rocks than Gryposaurus). Otherwise, the skull of Kritosaurus is incompletely known, lacking most of the bones in front of the eyes, but very similar to that of Gryposaurus.[11]

The following is a cladogram based on the phylogenetic analysis conducted by Prieto-Márquez and Wagner in 2012, showing the relationships of Gryposaurus among the other Kritosaurini: