 The synonymization of Kritosaurus and Gryposaurus that lasted from the 1910s to 1990 led to a distorted picture of what the original Kritosaurus material represented . Because the Canadian material was much more complete , most representations and discussions of Kritosaurus from the 1920s to 1990 are actually more applicable to Gryposaurus . This includes , for example , James Hopson 's discussion of hadrosaur cranial ornamentation , and the adaptation of this for the public in The Illustrated Encyclopedia of Dinosaurs . 
