Maiasaura

Maiasaura (from , and , the feminine form of saurus, ) is a large herbivorous saurolophine hadrosaurid ("duck-billed") dinosaur genus that lived in the area currently covered by the state of Montana and the Canadian province of Alberta, in the Upper Cretaceous (mid to late Campanian), from 86.3 to 70.6 million years ago. Maiasaura is the state fossil of Montana.

The first remains of Maiasaura were discovered in the Two Medicine Formation near Choteau, Montana in 1978 by Bynum, Montana resident Laurie Trexler. This holotype specimen was later described by Horner and Makela in 1979 as the new genus and species Maiasaura peeblesorum. The given genus name refers to the finding of eggs, embryos, and juveniles in a nest-like structure by Marion Brandvold in 1978 relatively close to the holotype specimen. This discovery of fifteen juvenile dinosaurs in close proximity to an adult showed the first instance of parental and social behavior in dinosaurs. It allowed for interpretations such as that Maiasaura fed its young while they were in the nest. Further work in this area led to the discovery of more dinosaur eggs, leading to the area being named "Egg Mountain". Hundreds of bones of Maiasaura have been discovered. Maiasaura was about long. Young animals walked on their hind legs, adults on all fours. Maiasaura was probably closely related to Brachylophosaurus.