 Corythosaurus / <unk> / is a genus of hadrosaurid " duck @-@ billed " dinosaur from the Upper Cretaceous Period , about 77 – 75 @.@ 7 million years ago . It lived in what is now North America . Its name means " helmet lizard " , derived from Greek <unk> . It was named and described in 1914 by Barnum Brown . Corythosaurus is now thought to be a lambeosaurine , related to <unk> , <unk> , Hypacrosaurus , and Olorotitan . Corythosaurus has an estimated length of 9 metres ( 30 ft ) , and has a skull , including the crest , that is 70 @.@ 8 centimetres ( 27 @.@ 9 in ) tall . 
