20.2" Hadrosaur (Edmontosaurus) Radius - South Dakota

Hadrosaurs are frequently referred to as duck-billed dinosaurs and are members of the Ornithischian family Hadrosauridae. They were fairly common herbivores that roamed Asia, Europe, and North America during the Upper Cretaceous Period. Many species of Hadrosaurs had distinctive crests on their heads, some of which had air-filled chambers that may have produced a distinct sound. These crests may have been used for both audio and visual display purposes.

Because of its age and sedimentary composition, the Hell Creek Formation has become one of the most paleontologically studied areas in the world. 158 genera of animals and 64 genera of plants are known from the formation and new discoveries are made frequently. In addition to Tyrannosaurs, Ceratopsids, and Hadrosaurs, the formation has yielded remains of amphibians, reptiles, lizards, snakes and turtles, fish and sharks, avian and non-avian dinosaurs, and mammals. The Hell Creek Formation gives the most complete understanding of the environment just before the Cretaceous-Paleogene extinction.