Maiasaura (from the Greek "μαία" and the feminine form of Latin saurus, meaning "good mother reptile" or "good mother lizard") is a large herbivorous hadrosaurid ("duck-billed") dinosaur genus that lived in the area currently covered by the state of Montana in the Upper Cretaceous Period (mid to late Campanian), about 76.7 million years ago.[1] The first fossils of Maiasaura were discovered in 1978. The genus was named in 1979. The name refers to the find of nests with eggs, embryos and young animals, in a nesting colony. These showed that Maiasaura fed its young while they were in the nest, the first time such evidence was obtained for a dinosaur. Hundreds of bones of Maiasaura have been dug up. Maiasaura was about 9 metres (30 ft) long. Young animals walked on their hind legs, adults on all fours. Maiasaura was probably closely related to Brachylophosaurus.