Hypacrosaurus

Hypacrosaurus was a large crested duck-billed dinosaur that lived during the Late Cretaceous period in what is now western North America. Discovered in Alberta and Montana, it is closely related to Corythosaurus but distinguished by its prominent high-spined vertebrae, which supported a muscular or fatty ridge along its back. Adults grew to around nine metres in length, possessing a hollow helmet-shaped crest that connected to the nasal passages. This crest was likely used for display as well as producing low-frequency vocal calls to communicate across ancient coastal lowlands. Hypacrosaurus is also remarkable for the exceptional preservation of its nesting sites, including fossilised eggs, embryos, and hatchlings. These discoveries have provided palaeontologists with crucial insights into the rapid growth rates and nesting habits of lambeosaurine dinosaurs.

It possessed extraordinarily tall neural spines along its back, forming a shallow ridge or sail above its hips.

Where and when

Hypacrosaurus lived in the Late Cretaceous, from 75 to 67 million years ago (Campanian-Maastrichtian age). Its remains come from Canada and United States, in the Horseshoe Canyon Formation.

The numbers

Length 8.6 m (estimates run from 8 to 9.1 m). Mass about 3.7 t. Hip height about 3.2 m. That is 5.1 human-lengths, or 0.77 of a double-decker bus. These are estimates from near-complete skeleton; fields marked estimated by the site are length, mass, hip height.

Compare Hypacrosaurus with a bus Place on the timeline