Maiasaura

Maiasaura was a large duck-billed dinosaur famous for revolutionising our understanding of dinosaur parenting. Discovered in the Late Cretaceous rocks of Montana, it lived roughly seventy-six million years ago along lush river floodplains. Growing up to nine metres long and weighing several tonnes, it possessed a small solid crest above its eyes and a broad beak backed by tightly packed dental batteries designed for grinding coarse plants. The discovery of Egg Mountain revealed vast nesting colonies containing fossilised nests, eggs, and developing young. Because the wear on hatchling teeth showed they had been eating plant matter while their leg joints remained too undeveloped to walk, scientists concluded parents actively tended and fed their young. Maiasaura lived in huge herds, relying on safety in numbers to protect their colonies from predators.

Nesting colonies of Maiasaura provided the first clear evidence that dinosaurs nurtured and fed their hatchlings.

Where and when

Maiasaura lived in the Late Cretaceous, from 77 to 75.5 million years ago (Campanian age). Its remains come from United States, in the Two Medicine Formation.

The numbers

Length 8.5 m (estimates run from 8 to 9 m). Mass about 3 t. Hip height about 2.5 m. That is 5 human-lengths, or 0.76 of a double-decker bus. These are estimates from near-complete skeleton; fields marked estimated by the site are length, mass, hip height.

Compare Maiasaura with a bus Place on the timeline