Description and Classification

Maiasaura was a large, plant-eating dinosaur, growing up to 9 meters (about 30 feet) long and weighing around 2 to 3 metric tons. It belonged to the Hadrosauridae family, a group known for their distinctive broad, flat snouts that resembled a duck’s bill. Specifically, Maiasaura is classified within the Saurolophinae subfamily (also known as hadrosaurines), which are generally characterized by lacking large, hollow crests, although some, like Maiasaura, had small, solid crests.

Like other hadrosaurs, Maiasaura could walk on its two strong hind legs (bipedally) or on all fours (quadrupedally), perhaps to graze on low-lying plants. Its mouth was equipped with hundreds of tightly packed teeth, forming “dental batteries” perfect for grinding tough plant material. It had a small, solid bony crest located on its snout, just in front of its eyes. This crest might have been used for display to attract mates or for head-butting contests within the species. It shared many features with other hadrosaurs like Edmontosaurus and Hadrosaurus.

Distinguishing Features

Maiasaura is distinguished by several key features, most notably its inferred parental care:

• Evidence of complex nesting behavior, including nests built in colonies and suggestions that adults cared for their young until they were large enough to leave the nest.
• A broad, duck-like beak used for cropping vegetation.
• Dental batteries composed of many rows of teeth designed for efficiently grinding plant matter.
• A small, solid, spiky crest on the top of its head, between and slightly in front of the eyes.
• Relatively large size compared to some other hadrosaurines.
• Fossil discoveries at “Egg Mountain” in Montana revealed large nesting grounds.

Paleoenvironment and Diet

Maiasaura lived in North America during the Late Cretaceous period. Its fossils are primarily found in the Two Medicine Formation of Montana. This area was an inland floodplain with a seasonal climate, characterized by forests and more open areas. Maiasaura shared this environment with a variety of other dinosaurs. Predators included tyrannosaurids like Daspletosaurus and smaller theropods like Bambiraptor. Other plant-eaters in the region included ceratopsians such as Einiosaurus and armored ankylosaurs.

Maiasaura was strictly a herbivore. It used its beak to snip off leaves, twigs, berries, and seeds from plants like conifers and flowering plants. The powerful dental batteries then ground this tough food. Evidence suggests that Maiasaura lived in large herds and migrated to nesting sites.

Significance and Ongoing Research

The discovery of Maiasaura and its nesting grounds was a landmark in paleontology. It dramatically changed scientists’ understanding of dinosaur behavior, providing some of the first strong evidence that some dinosaurs were not just egg-layers but also caring parents. The “Egg Mountain” site showed that these dinosaurs nested in colonies, much like some modern birds. This finding highlighted that some dinosaurs were social animals that lived in groups.

Ongoing research on Maiasaura continues to explore various aspects of its biology. Scientists study the growth rates of Maiasaura from hatchling to adult using bone histology (the study of bone tissue). Other research focuses on the biomechanics of how Maiasaura moved and chewed, the precise function of its small cranial crest, and its exact placement within the hadrosaur family tree. The study of Maiasaura continues to offer valuable insights into the lives of these fascinating prehistoric animals.