Hadrosaur fossils

Hadrosaurs

The Hadrosauridae, also known as the duck-billed dinosaurs, were members of the ornithischian ("bird-hipped") dinosaurs. They were herbivorous (plant eating), and could probably switch easily from walking bipedally (on two legs), to walking quadrupedally (on all four legs) depending on whether they were feeding or running from predators. 

The hadrosaur dinosaurs became the most common and well-adapted group of the ornithopod dinosaurs throughout the world. They probably first appeared in central Asia during the Cretaceous Period. By the late Cretaceous Period, they had spread all over the Northern Hemisphere, migrating into North America across the Bering Land Bridge. From North America, they travelled into South America. The southern landmass of Gondwanaland had broken up by this time, so hadrosaur dinosaur bones have not been found in Africa, Asia, or the Indian subcontinent.
The most noticeable feature of the hadrosaur dinosaurs was their broad, flattened snout which resembled the bill of a duck, resulting in their being called the duck-billed dinosaurs. Hadrosaurs did not have dinosaur teeth in the front of their mouths, but they had batteries of dinosaur teeth arranged in their upper and lower jaws in such a way as to form a grinding surface.

One of the factors that led to the success of the hadrosaurs was that they developed at the same time as the angiosperms (flowering plants). This meant that in addition to ferns, horsetails, cycads, and conifers (evergreen plants), the hadrosaurs were also able to feed on flowering plants. Grasses, however, did not appear until the late Eocene Epoch. The success of the hadrosaurs may have been a factor in the decline of other herbivorous dinosaurs, such as the iguanodonts (such as Iguanodon) and the sauropods.

In hadrosaur dinosaur teeth, you can see a part of the dinosaur tooth that is black, while the rest of the tooth is brown. The black part of the teeth is the chewing surface. The teeth then come together in off-set positions, to form a grinding surface.

Hadrosaurs had long hind dinosaur bones and shorter forelegs, with hoof-like dinosaur claws for walking on. Some species may have had skin between their toes that would have resembled the webbing of a duck's foot. This webbing, along with the duck-bill shape of their mouths, and their laterally compressed tails, has led many people to believe that the hadrosaurs may have been at least semi-aquatic. The small amount of webbing between their toes, however, probably would not have improved their swimming ability much.

Edmontosaurus (originally called Anatosaurus) was one of the first hadrosaur dinosaur fossils to be discovered. The name Anatosaurus means "duck lizard", and came from the duck-bill shape of its mouth.

Edmontosaurus is also important because two dessicated or "mummified" dinosaur fossils specimens were found. Such preservation of dinosaur skeletons is extremely rare, and can tell us a lot about the lives of these extinct animals. The stomach contents of these animals were also preserved, their last meal consisted of pine needles, twigs, seeds, and fruits. Although their skin had decomposed, impressions of their skin had been left in the surrounding sediment, and this shows us that Edmontosaurus had a thick, leathery hide. These dinosaur skeletons seemed to have webbing between their toes, but paleontologists believe that they were actually the dehydrated remains of weight-bearing walking pads, similar to the foot pads of modern camels.

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