It’s called the good mother lizard because the bones of juvenile Maiasaura dinosaurs as well as broken eggshells were found in the vicinity of adult dinosaur remains. In fact, 14 nests were found in one area! These discoveries led paleontologists to believe that Maiasaura dinosaurs cared for their young including protecting them from predators like Troodons.
This discovery was especially notable because paleontologists weren’t sure whether dinosaur parents cared for their young.