Duck-billed dinosaur or hadrosaur
Edmontosaurus annectens
(Cretaceous, Hell Creek Formation, Faith, South Dakota)
Hadrosaurus, or duck-billed dinosaurs, such as Edmontosaurus were among the most abundant of Late Cretaceous dinosaurs. Edmontosaurus fossils have been found in sedimentary formations of the Western Interior of North America including Alberta, Saskatchewon, North and South Dakota, Wyoming, Colorado and Montana. These animals probably lived in herds on the eastern flanks of the Cordilleran Mountains, an ancient mountain located approximately where the Rockies are today, and west of the Late Cretaceous Interior Seaway which extended from the Arctic to the Gulf of Mexico. Duck-billed dinosaurs were peacable herbivores whose natural enemies probably included the giant predator Tyrannosourius rex.