Dinosaurs - Hadrosaurs jaw (Edmontosaurus annectens). Cretaceous, Montana, USA, and Alberta, Canada. The photograph shows the tooth battery of a Hadrosaur (plant eating dinosaurs). They were self-sharpening teeth; new teeth emerged through the life of the animal as worn ones were dropped out.Specimen from Collections of the Black Hills Institute of Geological Research, Hill City, South Dakota, USA.