Maiasaura was large, attaining an adult length of about 9 meters (30 feet) and had the typical hadrosaurid flat beak and a thick nose. It had a small, spiky crest in front of its eyes. The crest may have been used in headbutting contests between males during the breeding season.
This dinosaur was herbivorous. It walked both on two (bipedal) or four (quadrupedal) legs and appeared to have no defense against predators, except, perhaps, its heavy muscular tail and its herd behaviour. These herds were extremely large and could have comprised as many as 10,000 individuals Maiasaura was discovered by dinosaur paleontologist Jack Horner (paleontologic advisor for the Jurassic Park movies) and Robert Makela. He named the dinosaur after finding a series of nests with remains of eggshells and hatchlings at "Egg Mountain", in rocks of the Two Medicine Formation near Choteau in western Montana. This was the first proof of giant dinosaurs raising and feeding their young. Over 200 specimens, in all age ranges, have been found.