Corythosaurus is an extinct genus of hadrosaurid dinosaur that lived in North America during the Late Cretaceous period. It is known as Hollowhorns in the Land Before Time series, along with other large-crested hadrosaurs (lambeosaurines). They are seen in many Land Before Time movies and episodes, starting with The Land Before Time V: The Mysterious Island. The opening of 'The Big Freeze reveals that they use their crests to whistle. Most Corythosaurus in the Land Before Time are colored in shades of brown and gray with light underbellies, varying from rich to dull. It appeared in Jurassic Park III.