Maiasaura

Maiasaura peeblesorum, whose name translates to 'good mother lizard,' is a large hadrosaurid (duck-billed) dinosaur that lived during the Late Cretaceous period. Discovered in Montana in 1978 by paleontologist Jack Horner and Robert Makela, Maiasaura revolutionized our understanding of dinosaur behavior. The fossils were found in a remarkable context: a massive nesting ground, now famously known as 'Egg Mountain,' containing nests, eggs, and the remains of individuals from hatchlings to adults. This provided the first clear evidence that some dinosaurs cared for their young. Physically, Maiasaura was a typical hadrosaur, reaching up to 9 meters (30 feet) in length. It possessed a distinctive flat, broad snout or 'duck-bill' and a small, solid crest in front of its eyes. It was bipedal when running but likely moved on all fours while grazing on tough plant material like conifers and ferns, which it ground with complex batteries of cheek teeth. The discovery of Maiasaura was a landmark event in paleontology. The nesting colonies, with nests spaced roughly the length of an adult female apart, suggested complex social and herding behaviors. Fossilized hatchlings found within the nests had underdeveloped leg joints, indicating they were altricial—unable to leave the nest immediately after birth and thus requiring parental care for food and protection. This contrasted sharply with the prevailing image of dinosaurs as solitary, reptilian brutes. Maiasaura demonstrated that sophisticated behaviors like parental care and social nesting strategies evolved long before modern birds, providing a crucial window into the life and ecology of these fascinating prehistoric animals.