Geological Museum KIGAM

Maasaura is a herbivorous ornithopod dinosaur that became famous in the 1970s in Montana, USA, with the discovery of large scale spawning grounds buried in volcanic ash. So-called the 'Egg Mountain', there are many nests, numerous eggs, and more than 200 skeletal fossils from juveniles to adults, and the growth stages of these dinosaurs have been studied in great detail. However, during the dry season of the floodplain around the rivers, a large group of about 10,000 Maiasaura came to the area periodically to nest and lay eggs, juveniles were hatched for a certain period, and it was revealed that the juveniles were cared for. This dinosaur's scientific name, Maiasaura, reflects the habits of those who have looked after their offsprings, like birds and mammals, like a good mother (maia in Greek).

The first scholar to study Maiasaura's collective spawning grounds and fossils was J. R. Horner, a curator of paleontology at the Museum of the Rockies in the United States. He discovered that the juveniles were cared for by their mother staying at the nest until the juvenile of about 30 cm grew up to be about one meter. The reason for his 'nursing dinosaur theory' was that the younger legs were not strong enough to travel a long distance, but their teeth were partly worn from eating food (Horner & Makela 1979, Horner 1982, Horner & Gorman 1988, Horner & Weishampel 1988, Horner & Dobb 1997, Morell 1987).