The hadrosaurs, or “duck-billed” dinosaurs, were some of the most peculiar dinosaurs that thrived during the Cretaceous period, as well as the last ornithopod group to ever appear. Amazingly, these dinosaurs were similar to modern ducks: they had beaks, webbed feet, and a pelvis like a duck. Hadrosaurs also had stiff tails supported by strong, bone-like tendons, and their lost teeth were rapidly replaced. These dinosaurs probably spent most of their lives close to bodies of water, feeding on tough plants; they apparently bore their young on higher ground in large nesting areas.

Most of the duck-billed dinosaurs are found in Late Cretaceous rocks in Europe, Asia, and North America. They are close relatives—and some say descendants—of the earlier iguanodontid dinosaurs. The two subfamilies of the hadrosaurs were the Lambeosaurinae and the Hadrosaurinae.