Say it: MY-ah-SORE-ah · Name means: “Good mother lizard”
Key facts about Maiasaura
⏳ Lived
77–75 million years ago Late Cretaceous
🌿 Diet
Herbivore (plant-eater)
📏 Length
7–9 m (23–30 ft)
↕️ Height
2–2.5 m (7–8 ft)
⚖️ Weight
2,500–4,000 kg (5,510–8,820 lb)
📍 Found in
North America
🔎 Discovered
1978 by Marion Brandvold (named by Jack Horner and Robert Makela, 1979)
About Maiasaura
Maiasaura was a duck-billed dinosaur that built nests and looked after its babies. Its name means 'good mother lizard'.
Maiasaura peeblesorum was a saurolophine hadrosaurid from the Campanian Two Medicine Formation of Montana. Nesting colonies with eggs, hatchlings and juveniles provided some of the first strong evidence that dinosaurs cared for their young.
Drawn to scale next to a 1.7 m adult and a 12 m school bus.
Did you know?
Maiasaura made nests out of mud and laid about 30 to 40 eggs in each one!
Its babies were small enough to fit in your arms, but grew to the length of a bus.
The nests were built close together, like a big dinosaur neighbourhood.
A piece of Maiasaura bone and eggshell was taken into space by an astronaut in 1985!
Nests at Egg Mountain were spaced about 7 m apart, less than an adult's body length, similar to colonies of modern seabirds.
Hatchlings had poorly formed leg joints and worn teeth, which Horner and Makela interpreted as evidence that babies stayed in the nest and were fed by parents; some researchers think the worn teeth could have formed before hatching.
A 2015 study of 50 shin bones found that Maiasaura grew very fast as youngsters and that about 90% died in their first year; survivors faced much lower risk until death rates rose again from about age eight.
Bonebeds in the Two Medicine Formation suggest herds of thousands, with one estimate of up to 10,000 animals buried together, possibly after a volcanic ash event.
Cropped plants with a wide, toothless beak and ground them down with dental batteries of hundreds of packed teeth; adults may have brought food to babies in the nest.
Clues scientists use: dental batteries with grinding surfaces; tooth wear; coprolites full of decayed conifer wood from the same rock layers; worn teeth in nestlings, hinting they were already eating plants.
Who might have hunted it: Daspletosaurus, Troodontids (eggs and babies).
🗺️ Where fossils were found
Egg Mountain, near Choteau, Montana, USA (North America)
Two Medicine Formation, Glacier County, Montana, USA (North America)
Oldman Formation, Alberta, Canada (North America)
Skeleton / museum mount of Maiasaura: Maiasaura peeblesorum skeletal mount, Brussels Natural History museum…
Myth or fact?
✗ Myth: All dinosaurs laid their eggs and walked away, like turtles.
✓ Fact: Maiasaura nesting grounds, with babies of different ages still in and around nests, show that at least some dinosaurs cared for their young.
✗ Myth: Duck-billed dinosaurs lived mainly in water.
✓ Fact: Maiasaura nested on dry upland ground and ate tough land plants, including rotting wood.
✏️ Quick quiz
Circle the right answer. Name: ______________________
What does 'Maiasaura' mean?
A Fast runner
B Big egg
C Duck lizard
D Good mother lizard
What did Maiasaura build for its eggs?
A Nests
B Caves
C Treehouses
D Underwater burrows
In which US state was Maiasaura discovered?
A Texas
B Florida
C Montana
D Alaska
Answers: 1–D 2–A 3–C
Sources and picture credits
Natural History Museum London — Maiasaura — www.nhm.ac.uk/discover/dino-directory/maiasaura.html
Wikipedia — Maiasaura — en.wikipedia.org/wiki/Maiasaura
DinoVerse · Dinosaur fact sheet
