Maiasaura

Maiasaura was a large hadrosaurid dinosaur that roamed the coastal plains of what is now Montana and Alberta during the Late Cretaceous, roughly 76-80 million years ago. Growing up to 9 meters long, these duck-billed herbivores traveled in massive herds that may have numbered in the thousands, leaving behind one of the most spectacular fossil assemblages ever discovered.

The discovery of Maiasaura in 1978 by paleontologist Jack Horner and amateur fossil hunter Marion Brandvold fundamentally changed our understanding of dinosaur behavior. At a site called Egg Mountain in Montana, they found nesting colonies containing eggs, embryos, juveniles, and adults — evidence that these dinosaurs returned to the same nesting grounds year after year and cared for their young until they were large enough to leave the nest. The babies' leg bones weren't fully developed at hatching, meaning they couldn't walk well and depended on parental care.

Maiasaura fed on low-growing vegetation using its distinctive duck-like bill to crop plants, then processed them with hundreds of tightly packed teeth arranged in dental batteries. These teeth were continuously replaced throughout life, allowing efficient grinding of tough plant material. Bone analysis suggests these dinosaurs grew remarkably fast — reaching near-adult size in about eight years.

In 1985, Maiasaura became Montana's official state fossil, and in 1996, a piece of Maiasaura bone was carried into space aboard the Space Shuttle, making it one of the few dinosaurs to leave Earth — even if only as a fossil.