Maiasaura << MAY uh sawr uh >> was a large, plant-eating dinosaur noted for its nesting behavior. Its name means good mother lizard, though dinosaurs were not lizards. Evidence suggests that its hatchlings were completely dependent on their parents for food and protection. Maiasaura lived about 75 to 80 million years ago in the area of what is now Montana. It belonged to a group of dinosaurs called hadrosaurs.
Maiasaura reached about 23 to 30 feet (7 to 9 meters) long. It weighed about 2 to 4 tons (1.3 to 3.6 metric tons). Like other hadrosaurs, it could walk on two legs or four.
Maiasaura had a large gut. It also had powerful jaws lined with hundreds of teeth. These features enabled it to grind up large amounts of low-growing ground plants. It could stand on its hind legs to reach higher vegetation. Fossils suggest that it might also have eaten decaying wood, which could have provided nutrition from fungi and insects.
Maiasaura lived in large herds that may have migrated with the changing seasons. Fossils show that these herds could have thousands of members. The migrations likely helped Maiasaura find fresh plants to eat.
Maiasaura also nested in large colonies. They scooped nests out of the ground that were about 6 1/2 feet (2 meters) across. Each nest probably held as many as 15 to 20 young. Nesting colonies contained Maiasaura at various stages of growth, including juveniles. Fossils suggest that the young grew to at least about a quarter of adult length before leaving the nest. Young may have reached adult size in as little as five years.
See also: Dinosaur (Ornithopods); Hadrosaur.
