Corythosaurus started developing its crest when half the size of adults , but Parasaurolophus juveniles grew crests when only 25 % as long as adults . Juvenile Corythosaurus , along with adults , had a premaxilla @-@ nasal fontanelle . Young and adult Corythosaurus are similar to Lambeosaurus and Hypacrosaurus but dissimilar to Parasaurolophus in that the sutures of the skull are sinuous , and not smooth and straight . This feature help differentiate parasaurolophins from lambeosaurins . Generally , the crests of juveniles of lambeosaurines like Corythosaurus , Lambeosaurus , Hypacrosaurus stebingeri , parasaurolophines like Parasaurolophus , and primitive lambeosaurines like Kazaklambia are quite alike , although other features can be used to distinguish them .