Edmontosaurus (Ed-mont-oh-soar-us) is the classic example of the duck-billed dinosaur (hadrosaur). It was 40 feet in length and lived during the Late Cretaceous Period. It was one of the very last dinosaurs.
Edmontosaurus lacked the bizarre cranial crest that is characteristic of so many hadrosaurs and had a particularly broad and flat beak, enhancing its duck-like appearance. There was, evidently, a frill that ran down the spine from the neck to the tail, a characteristic that may have been common to all duck-bills.
Edmontosaurus is known from numerous excellently preserved skeletons, including two rather remarkable "mummified" specimens. These specimens apparently represent dinosaurs whose carcasses lay undisturbed for a considerable period of time, exposed to the sun and dry air.
Edmontosaurus "mummy" at the American Museum of Natural History
The dinosaur's tissues dried out and hardened, and the skin was drawn tightly over the bones. The mummy was then quickly buried in mud or fine-grained silt, perhaps due to a sudden flood. The fine-grained sediment produced an exact impression of the skin, but the skin itself was not preserved. These specimens clearly show that the skin was covered with bump-like scales or tubercles that did not overlap and formed definite patterns across the body. It is possible that these patterns were reflected by differences in body coloration on the living animal, but that is pure speculation.
The fingers of the forelimb were evidently encased in flesh, giving the hand a peculiar "mitten"-like appearance. When seen on the mummies, this was originally interpreted as webbing between the fingers and contributed to a long-standing belief that duck-bills were aquatic.
Edmontosaurus is sometimes known by the name Trachodon (Track-oh-don) or Anatosaurus (A-nat-oh-soar-us).