Dinosaurs

Updated: February 3, 2026

Dinosaurs lived on Earth for more than 160 million years, from about 230 million years ago until around 66 million years ago. During the Late Cretaceous period, what is now Montana lay along the edge of a shallow inland sea, with broad river plains and forests that made excellent habitat for many kinds of dinosaurs.

Maiasaura, Montana's State Fossil

Montana's official state fossil is Maiasaura peeblesorum, a plant-eating "duck-billed" dinosaur whose name means "good mother lizard" or "caring mother lizard." Scientists chose this name because fossils from Montana show that Maiasaura nested in groups and cared for their babies. At sites in the Two Medicine Formation, researchers have found bowl-shaped nests, eggs, and the bones of hatchlings and juveniles together, sometimes with plant material that may have been used as food or nesting material.

At one nesting ground, there are many nests close together with young at different growth stages, which tells scientists that adult dinosaurs probably returned to the same area and raised their young in colonies. Studies of Maiasaura bones show that the babies grew very quickly, from tiny hatchlings to two-ton adults in less than ten years, so they likely depended on parents for protection and food when they were small. These discoveries helped change the old picture of dinosaurs by showing that at least some species were active, social animals and attentive parents, not just slow, lonely reptiles.

Egg Mountain and Dinosaur Nests

One of the world's most important dinosaur nesting sites is Egg Mountain, near Choteau, Montana. In the late 1970s and early 1980s, paleontologists working there uncovered some of the first well-documented dinosaur nests, eggs, and baby skeletons in North America, including several Maiasaura nests all preserved in the same rock layers. The site also preserves tiny fossils of mammals, insects, and plants that help scientists reconstruct the ancient environment.

Because Egg Mountain and the nearby Willow Creek area provided the first strong evidence that some dinosaurs built nests, lived in nesting colonies, and cared for their young, these Cretaceous nesting grounds are now recognized internationally as a geoheritage site-meaning they are considered scientifically important to the whole world. Ongoing research there continues to improve what scientists know about dinosaur growth, behavior, and ecosystems.

Learning About Dinosaurs in Montana Today

Montana is still one of the best places to explore dinosaur science. The Montana Dinosaur Trail connects museums and discovery centers across the state; it currently includes about 14 official stops, with additional sites being added over time. These stops stretch from the Rocky Mountain Front to the prairies of eastern Montana.

Along the trail, visitors can see real fossils, life-size skeletons, and interactive exhibits that explain how dinosaurs lived, moved, and grew. Some museums and field stations offer summer digs, talks by working paleontologists, and hands-on activities where kids can try "excavating" replica fossils. If you are fascinated by dinosaurs-or you want to stand where major discoveries about dinosaur families and parenting were made-Montana is still one of the best places in the world to visit.

• Dinosaur Facts
• Maiasaur
• Jack Horner
• Montana Dinosaur Activities
• Montana Dinosaurs
• Montana Dinosaur Trail

Updated: February 3, 2026