LATE CRETACEOUS
HELL CREEK FORMATION
Hadrosaurs
At the Hell Creek formation ornithopods reached their apex in the duck-bills. These were unarmored, they development of a horny beak, complex dentle batteries, an elongated pubis and were adapted to eating while bent over. They became semi-quadruped; still running on two legs, and comfortable reaching up into trees; but spending most of their time walking or grazing while on all fours. Ornithopods became larger, the very largest were as heavy as medium sized sauropods.
mouse over diorama pics for figure information.
Hadrosaurus was the first dinosaur discovered in America and the first specimen mounted in a museum. The partial skeleton discovered in 1859 indicated that some dinosaurs were bipedal, 
and it has been made the fossil emblem of New Jersey and a noted tourist attraction. The lack of a skull means that it cannot be classified other than as a hadrosaurid of indeterminate genus. The name has been retained for historical reasons. It is one of the most compete fossils found in the eastern North America. The fossil was distintly bipedal and the reconstruction used Kangaroos as the template.
Trachodon was orignially named based on the crown of a large tooth. It may turn out to be the senior synonym of either Prosaurolophus or Corythosaurus, or possibly a ceratopsian, depending on the tooth structure.
Originally all Hell Creek hadrosaur species were associated with Trachodon, no longer considered a vaild species.
As a hadrosaurid, Trachodon would have been a large, bipedal/quadruped herbivore traditionally modeled with a kangaroo posture. Many of the fossils asigned to Trachodon were reassigned to Edmontosaurus, Anatotian and Anatosaurus. These were consolidated into edmontosaur species.
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