Maiasaura was a duck-billed dinosaur that lived in what is now Montana about 76.7 million years ago during the Late Cretaceous Period. Its name means good mother lizard because fossils suggest adults cared for eggs and young in large nesting colonies. Maiasaura is important because it gives paleontologists rare evidence about dinosaur growth, social behavior, and reproduction.
The discovery of nests, eggs, hatchlings, juveniles, and adults in one region makes it one of the best-studied dinosaurs.
Key Facts
- Maiasaura lived about 76.7 million years ago in the Late Cretaceous Period.
- Adult Maiasaura were about 9 m long and may have weighed roughly 3,000 kg.
- Maiasaura was a hadrosaur, a plant-eating duck-billed dinosaur with grinding teeth.
- Growth rate can be estimated with change in length per time: growth rate = Δlength / Δtime.
- Fossil nests were found in colonies, suggesting repeated nesting behavior and social organization.
- Hatchlings had underdeveloped limb bones, which suggests they may have stayed in the nest and received care.
Vocabulary
- Maiasaura
- Maiasaura was a large plant-eating hadrosaur dinosaur known for fossil evidence of nesting colonies and possible parental care.
- Hadrosaur
- A hadrosaur is a duck-billed herbivorous dinosaur with specialized teeth for grinding plants.
- Nesting colony
- A nesting colony is a place where many animals build nests close together, often returning to the same area to reproduce.
- Fossil bed
- A fossil bed is a layer of rock that contains many preserved remains or traces of ancient organisms.
- Ontogeny
- Ontogeny is the growth and development of an organism from embryo to adult.
Common Mistakes to Avoid
- Calling Maiasaura a carnivore is wrong because its beak, teeth, and body plan show it was adapted for eating plants.
- Assuming good mother lizard proves modern-style parenting is wrong because the name reflects evidence-based interpretation, not direct observation of behavior.
- Thinking all dinosaur eggs in a nest belonged to one species is wrong because paleontologists must compare eggs, embryos, bones, and rock layers before making that conclusion.
- Treating fossil size as exact body size is wrong because fossils can be incomplete, distorted, or from individuals of different ages.
Practice Questions
- 1 An adult Maiasaura is estimated to be 9 m long. If a juvenile fossil is 3 m long, what fraction of the adult length is the juvenile?
- 2 A young Maiasaura grows from 1.0 m to 4.0 m in 3 years. What is its average growth rate in meters per year?
- 3 Fossils of eggs, hatchlings, juveniles, and adults are found together in repeated nest layers. Explain how this evidence supports the idea that Maiasaura lived in nesting colonies and may have cared for young.