 Hypacrosaurus ( meaning " near the highest lizard " [ Greek υπο- , hypo- = less + ακρος , akros , high ] , because it was almost but not quite as large as Tyrannosaurus ) was a genus of duckbill dinosaur similar in appearance to Corythosaurus . Like Corythosaurus , it had a tall , hollow rounded crest , although not as large or as tall as Corythosaurus 's. Unterscheidung Hypacrosaurus-Corythosaurus. Hypacrosaurus is a genus of hadrosaurid dinosaurs. Hypacrosaurus is a genus of hadrosaurid dinosaurs. Hypacrosaurus