Hadrosaurus, “sturdy lizard” was found in a marl pit in Haddonfield, New Jersey, in 1858 and was the first dinosaur in North America that was known from more than isolated teeth, and it became the first mounted dinosaur skeleton ten years later. It was discovered by William Parker Foulke and described by Joseph Leidy in the same year of its discovery. Though it is known only from incomplete remains–comprised of a pelvis, an arm, a leg, a piece of the jaw, and some vertebrae–it is still considered a valid genus of dinosaur. Hadrosaurus lived during the Late Cretaceous period, approximately 75 million years ago. It was a relatively large dinosaur, measuring 8 m (26 ft) in length, over 2 m (6.5 ft) in height, and weighing in at 3 tons.
Dr. Alan Grant and the kids saw hadrosaurs in the Apatosaurus paddock, and escaped being trampled by them and the Maiasaura herd. Hadrosaurus did not have any fragments of amphibian DNA and were therefore never observed as breeding; their expected and actual population stayed at eleven until equilibrium dropped their population to five. The hadrosaurs’ last logged version was 3.1.