2007 Schools Wikipedia Selection. Related subjects: Dinosaurs

iMaiasaura peeblesorum
Fossil range: Late Cretaceous
Maiasaur with hatchlings, at the Wyoming Dinosaur Center
Maiasaur with hatchlings, at the Wyoming Dinosaur Centre
Conservation status
Extinct (fossil)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Superorder: Dinosauria
Order: Ornithischia
Suborder: Ornithopoda
Infraorder: Iguanodontia
Superfamily: Hadrosauroidea
Family: Hadrosauridae
Subfamily: Hadrosaurinae
Tribe: Maiasaurini
Genus: Maiasaura
Horner & Makela, 1979
Species: M. peeblesorum
Binomial name
Maiasaura peeblesorum
Horner & Makela, 1979

Maiasaura peeblesorum ("Peebles' good mother lizard") is a large duck-billed dinosaur species that lived in Montana in the Upper Cretaceous Period ( Campanian), about 74 million years ago.


Maiasaura was discovered by dinosaur paleontologist Jack Horner (paleontologic advisor for the Jurassic Park movies). He named the dinosaur after finding a series of nests with remains of eggshells and hatchlings. This was the first proof of giant dinosaurs raising and feeding their young. Over 200 specimens, in all age ranges, have been found.


Right femur of Maiasaura.
Right femur of Maiasaura.

Maiasaura had a strange appearance. It was large (about 7 meters long) and it had the typical hadrosaurid flat beak and a thick nose. It had a small, spiky crest in front of its eyes. The form of the head resembled that of a horse.

This dinosaur was herbivorous. It walked both on two ( bipedal) or four ( quadrupedal) legs and appeared to have no defense against predators, except, perhaps, its heavy muscular tail and its herd behaviour.

It lived in herds and it raised its young in nesting colonies. The nests, containing 30 to 40 eggs, were made of earth and were guarded by the parents (parental care). The eggs were about the size of ostrich eggs, so the hatchlings had to grow fast.

Maiasaura lived alongside the ceratopsid Centrosaurus, the tank-like Euoplocephalus and an earlier relative of Tyrannosaurus rex, Daspletosaurus torosus. It was among the latest dinosaur species to evolve, prior to the Cretaceous-Tertiary extinction of 65 million years ago.

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