Maiasaura (pronounced MY-ah-SORE-ah) was a duck-billed dinosaur that grew about 30 feet long, 8 feet tall, and weighed up to 4 tons. It had a flat skull and small crests in front of its eyes. This plant-eater had a toothless beak, cheek pouches, and many self-sharpening cheek teeth. Hard enamel was found on both the outer surface of the upper teeth and the inner surface of the lower teeth.

Maiasaura’s hands each had four fingers, and its feet had hoof-like claws. Maiasaura walked on four legs, and was a moderately fast dinosaur. Its front legs were much shorter than the rear legs. When Maiasaura ran, it probably only used the back legs, with the tail providing balance. Running was this dinosaur’s only means of escaping carnivores like Albertosaurus and Troodon.


Maiasaura was a large, plant-eating dinosaur. An adult would need to eat about 200 pounds of leaves, berries and seeds per day.


This dinosaur was first discovered in Montana. Since then, thousands of Maiasaura fossils (adults, hatchlings, juveniles, nests, eggs and embryos) have been found in western Canada and the United States. Marion Brandvold and her son David Trexler found one huge bone bed in Montana dubbed Egg Mountain. Jack R. Horner & Robert Makela named Maiasaura in 1979.


Maiasaura lived during the late Cretaceous period. It was among the last of the dinosaur species to evolve before the Cretaceous-Tertiary extinction 65 million years ago. Other dinosaurs of this time were Velociraptor, Albertosaurus and Troodon (carnivores that probably preyed upon Maiasauras), Tyrannosaurus rex (a larger version of Albertosaurus), Ankylosaurus (an armored herbivore), Parasaurolophus, Corythosaurus (a crested dinosaur), and Dryptosaurus (a meat-eating dinosaur).

Birth & Offspring

Maiasaura was the first dinosaur found alongside its young, eggs, and nests. This suggests that Maiasaura nurtured its young. The nests were holes scooped out of the ground, about 6-7 feet in diameter, and they contained up to 25 grapefruit-sized eggs each. Newly hatched Maiasaura babies were about 1 foot long.

In Montana, Maiasaura fossils were found in a huge group of about 10,000, strongly suggesting herding behavior. The nests were grouped in colonies, most likely for better protection against predators. The existence of herds might also suggest the necessity to migrate for food.


On the intelligence scale, Maiasaura was midway among the dinosaurs.

Archiwum: wrzesień 2022

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