Maiasaura peeblesorum MY-uh-SOR-uh
"Good mother lizard"
You 1.8 m (5.9 ft) tall
Maiasaura 9 m (29.5 ft) long
6 people holding hands
- Length
- 9 m (29.5 ft) — About 9 m long, ~2.5 tonnes — known from nesting colonies.
- Period
- Late Cretaceous (76–74 Mya)
- Place
- North America · Montana
- Food
- Herbivore — Tough plants chewed up first by parents, then probably regurgitated to feed hatchlings.
Maiasaura got its name — ‘good mother lizard’ — from a discovery that changed how we think about dinosaurs. Jack Horner and Bob Makela found a nesting colony in Montana in the late 1970s, with dozens of nests laid out in rows. Each nest contained eggs and bones of babies too big to be newborns but with unworn teeth, meaning the parents were bringing food back to them.
What we know
- First dinosaur with strong evidence of parental care — found in a nesting colony.
- Nests laid out in rows, each one body-length apart.
- Babies grew from 45 cm to ~1.5 m in one year — extremely fast growth.
- Lived in vast herds — bonebeds preserve thousands of individuals together.
What we guess
- How long the young stayed at the nest — months, based on tooth wear.
- What the parents fed them — chewed plant material is the leading guess.
- Whether the nesting colony was annual or just a one-time event.