Hypacrosaurus (meaning "almost the largest lizard") was a large, plant-eating, hollow-crested duck-billed dinosaur similar to Corythosaurus. It was about 30 feet (9 m) long, had almost 40 rows of cheek teeth, and a short toothless beak. A row of long spines from its vertebrae formed a high fin along its back. The fossils are dated as 75 to 67 million years ago.
Temporal range: Upper Cretaceous 75–67 mya
It is known from the remains of two species in the Upper Cretaceous of Alberta, Canada, and Montana, United States. It is the latest hollow-crested duckbill known from good remains in North America. It was an obscure genus until the discovery in the 1990s of nests, eggs, and hatchlings belonging to one of the species.
- Horner, John R.; Currie, Phillip J. (1994). "Embryonic and neonatal morphology and ontogeny of a new species of Hypacrosaurus (Ornithischia, Lambeosauridae) from Montana and Alberta". In Carpenter, Kenneth; Hirsch, Karl F.; Horner John R. (eds.) (eds.). Dinosaur Eggs and Babies. Cambridge: Cambridge University Press. pp. 312–336. ISBN 0-521-56723-8.CS1 maint: extra text: editors list (link)