 Corythosaurus is currently classified as a hadrosaurid , in the subfamily <unk> . It is related to other hadrosaurs such as Hypacrosaurus , Lambeosaurus and Olorotitan , with the exception of Olorotitan they all share similar looking skulls and crests . However , research published in 2003 has suggested that even though it possesses a unique crest , Olorotitan is Corythosaurus closest known relative . Benson et al . ( 2012 ) found that Corythosaurus was closely related to <unk> , <unk> , and Hypacrosaurus , and said that they formed a group of fan @-@ crested lambeosaurines . 
