Hypacrosaurus
hi-PAK-roh-SORE-us
"near the highest lizard"
- Lived
- 84 to 66 million years ago, Late Cretaceous
- Diet
- Herbivore
- Length
- about 9 m (30 ft)
- Group
- Ornithopods, Hadrosauridae
- Found in
- Canada and United States
- Named by
- Brown 1913
Size comparison
To scale
Scale in metersOutline: typical ornithopod shape
Where its fossils were found
The evidence
Today
75 million years ago
Habitat
It lived among rivers and floodplains in Alberta and Montana. Daspletosaurus, Euoplocephalus and Struthiomimus were among the dinosaurs of its wider world.
Field notes
About Hypacrosaurus
What it was like
Hypacrosaurus was a duck-billed plant eater about 9 meters (30 feet) long. It had a rounded, hollow crest on top of its head, a little like that of its close relative Corythosaurus, and a tall ridge of spines along its back.
The hollow crest held long air passages that may have helped it make loud, low calls. Like other duckbills, it ground tough plants with rows of tightly packed teeth.
Its world
It lived in the Late Cretaceous in what is now Alberta in Canada and Montana in the United States. Its bones come from rocks such as the Horseshoe Canyon and Two Medicine formations. Predators such as Daspletosaurus shared its world, along with the smaller hunter Troodon and the ostrich-like Struthiomimus.
How it was found
Brown named Hypacrosaurus in 1913. There are 34 recorded finds, including nests, eggs and hatchlings from Montana. These babies have helped scientists study how duckbills grew up, and how their crests developed as they aged.
Field gallery
More views of Hypacrosaurus
Scenes reconstructed from the available fossil evidence.
1 of 3
Lived alongside
Found in the same rock formations
A rock formation can hold fossils laid down millions of years apart, so not every animal here met Hypacrosaurus.
The evidence
The science behind Hypacrosaurus
Which parts of the picture come from its own bones, and which come from its relatives.
From its own fossils
- Skulls of different ages show a rounded, hollow crest developing from a crestless young head.
- Eggs preserve embryos with tiny teeth that contain daily growth lines.
- Growth rings inside its leg bones record rapid growth toward adult size.
Borrowed from relatives
- Its head shape and growth are known from its own skulls; Corythosaurus provides the closest comparison for crest development.
- Corythosaurus and Lambeosaurus help explain how a hollow crest may have worked in communication.
Still unknown
- The exact sound of its calls.
- Its color and whether the crest looked different in males and females.
- How much care adults gave their hatchlings.
Discovery timeline
- 1913Named itBrown
- 2008Growing upCooper et al.
- 2009SkullEvans, Ridgely & Witmer
- 2010SkullEVANS
- 2017Growing upErickson et al.
Key papers
The research behind what we know of Hypacrosaurus
Named it
Named Hypacrosaurus from a partial skeleton with unusually tall spines along the back.
A new trachodont dinosaur, Hypacrosaurus, from the Edmonton Cretaceous of Alberta. Bulletin of the American Museum of Natural History 32: 395-406
No link available
Growing up
Used growth rings in leg bones to reconstruct rapid growth in Hypacrosaurus and compare it with the growth of predators.
Relative growth rates of predator and prey dinosaurs reflect effects of predation. Proceedings of the Royal Society B: Biological Sciences 275: 2609-2615
Read the paper : Relative growth rates of predator and prey dinosaurs reflect effects of predation (opens in a new tab)Skull
Compared brains and inner ears in crested duckbills, supporting a role for their crests in communication.
Endocranial Anatomy of Lambeosaurine Hadrosaurids (Dinosauria: Ornithischia): A Sensorineural Perspective on Cranial Crest Function. The Anatomical Record 292: 1315-1337
Read the paper : Endocranial Anatomy of Lambeosaurine Hadrosaurids (Dinosauria: Ornithischia): A Sensorineural Perspective on Cranial Crest Function (opens in a new tab)Skull
Compared young and adult skulls, showing how the hollow crest developed and how its growth resembled that of Corythosaurus.
Cranial anatomy and systematics of Hypacrosaurus altispinus, and a comparative analysis of skull growth in lambeosaurine hadrosaurids (Dinosauria: Ornithischia). Zoological Journal of the Linnean Society 159: 398-434
Read the paper : Cranial anatomy and systematics of Hypacrosaurus altispinus, and a comparative analysis of skull growth in lambeosaurine hadrosaurids (Dinosauria: Ornithischia) (opens in a new tab)Growing up
Counted daily lines in embryonic teeth, finding that the eggs took months to hatch rather than developing as quickly as bird eggs.
Dinosaur incubation periods directly determined from growth-line counts in embryonic teeth show reptilian-grade development. Proceedings of the National Academy of Sciences 114: 540-545
Read the paper : Dinosaur incubation periods directly determined from growth-line counts in embryonic teeth show reptilian-grade development (opens in a new tab)
Close relatives
Other members of Hadrosauridae
Sources: Wikidata