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Maiasaura adults were about 30 feet (9.1 meters) long, and weighed 3 to 4 tons. The creature could walk on two or four legs, and had no obvious defenses against predators except for its heavy muscular tail, and the fact that it lived in large herds (some herds many have consisted of as many as 10,000 individuals).
When Maiasaura was first discovered in western Montana in 1978 by "Jack" Horner and Robert Makela, a complete nesting site was found, where the dinosaurs laid their eggs, and nutured their young. The nests were mounds of mud, with a depression in the center of each mound. The eggs had been laid with great care, arranged in circles and layers within the depression, each nest containing 30 to 40 eggs, each about the size of an ostrich egg. Scientists believe that Maiasaura would probably have covered each layer of eggs with sand or earth, to protect them from predators, and to keep the eggs warm. Although the parents are not believed to have sat on the nests, it is highly likely that heat generated by rotting vegetation in the nest, contributed to warming the eggs.
The name Maiasaura means "Good Mother Lizard", and was chosen in honor of the fact that it was the first dinosaur species discovered with clear and convincing evidence that it cared for its young. This includes the fact that fossils of baby Maiasaura show that the hatchlings' legs were not fully developed, and were incapable of walking, yet also show partially worn teeth, indicating that the adults brought food to the nest.
Maiasaura has been designated the official state fossil of Montana, since 1985.
Maiasaura was the first dinosaur in space. A Maiasaura egg-shell, and a piece of bone from a baby Maiasaura, were taken into space by NASA in 1985.
Maiasaura was a herbivore (plant-eater) that lived from 80 to 65 million years ago
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