Period: Late Cretaceous
Order, Suborder, Family: Ornithischia, Ornithopoda, Hadrosauridae
Location: North America (Canada, United States)
Length: 30 feet (9 meters)
The head of Hypacrosaurus looked much like Corythosaurus. The snout was somewhat ducklike, although the nostrils were in slightly different places. The crest of Hypacrosaurus was shaped like a corinthian helmet, but more pointed at the top. The back of the skull was also similar.
The striking differences between the two were in the skeleton, especially the backbone. Corythosaurus had moderate-size spines on its vertebrae (back bones). But Hypacrosaurus had very tall spines on its vertebrae. This is how it got its name, which means "high-spined reptile." These tall spines may have allowed for extra back muscles, but they also formed a sail. This sail would have captured the heat of the sun in the morning or released heat to cool the animal off on a hot day. In any case, these long spines would have made the animal look larger.
Like all other lambeosaurines, the crest of Hypacrosaurus contained a complex nasal cavity on top of its head. When it breathed, air was drawn in and out of the crest through a series of tubes and chambers that connected the nostrils to the back of the throat. The animal could also make sounds with its crest. Because of the size and shape of the crest, the sounds produced would have been low notes. It probably used these sounds to communicate with other members of its troupe or herd.