Hadrosaurids get their common name, "duck-billed dinosaurs," from their broad, flattened snouts, but the resemblance to a duck ends there. Behind that beak sat one of the most sophisticated chewing systems of any dinosaur: a dental battery of hundreds of interlocking teeth, constantly replaced, that ground tough Late Cretaceous vegetation the way a millstone grinds grain. Hadrosaurids walked on two or four legs depending on speed and activity, and many species carried elaborate hollow crests on the skull -- some tube-shaped, some fan-like -- that likely functioned as resonating chambers for species-specific calls as much as visual signals.
The family was overwhelmingly successful in its final 20-odd million years, radiating into dozens of genera across North America and Asia, with additional finds in Europe and South America. Crested genera like Parasaurolophus, Lambeosaurus, and Corythosaurus lived alongside crestless forms such as Edmontosaurus and Maiasaura -- the latter one of the first dinosaurs directly linked to nesting colonies and parental care. Shantungosaurus, from China, ranks among the largest ornithopods ever found.