Hadrosaur Rib Bone, from Lance Creek Formation, Weston County, Wyoming, U.S.A. (REF:HDB16)

Hadrosaurs ("duck billed’ dinosaur) were a group of herbivorous dinosaurs from the Cretaceous period.  Descended from Iguanodon-like ancestors, these dinosaurs as the name suggests had a duck-bill like mouth, which varied in shape depending on their diet, they had multiple rows of cheek teeth, which were used as a grinding surface. 

Some had crests on top of their heads, this is much discussed as to its purpose. Its use as a social function being widely accepted, possibly in courtship or communication such as warnings and through some fossil finds it thought that Hadrosaurs had good eye sight and hearing. With a lack of obvious defences it’s generally considered to be living in large herds, running at speed from large carnivores, such as T-Rex. 

Hadrosaurs could range from 10ft - 65ft long and lived in the Late Cretaceous with fossils found in North America, Europe and Asia.