Dinosaurs with almost complete fossil skeletons give us clues about what they were like. We get a good idea of the dinosaurs' size, weight, and appearance in life. The cell structure of fossilized dinosaur bones can tell us about the biology of a dinosaur. We then have information about how rapidly they grew, and perhaps about whether they were warm-blooded or cold-blooded. Fossilized bones sometimes leave evidence of bone diseases and the tooth marks of predators. Muscle tissue is almost never preserved (only two good "dinosaur mummies," with soft parts intact, have been discovered). But we can still tell how dinosaurs moved from the traces of ligaments and muscle scars on the bones.
Dinosaurs' teeth can tell us what kinds of foods they ate. Occasionally the actual stomach contents are preserved, so scientists can study what a dinosaur had for its last meal. The smooth "stomach stones" with which some dinosaurs ground up their food are sometimes preserved, and even fossilized dinosaur droppings, which are known as coprolites, have been found. All this gives us more information on dinosaur diets.
Fossilized skin impressions can be seen on very well preserved skeletons. The fine-grained sandy rocks of Dinosaur Provincial Park in Alberta, Canada, have preserved the skin impressions of duckbilled and horned dinosaurs. These provide an idea of what dinosaur skin looked like. No dinosaur has ever been found with feather traces, so there is no evidence that any dinosaur had feathers.
Scientists study locations and distribution of dinosaur bones for information about the dinosaurs' environments. The direction in which bones are pointed and the way they are arranged in dinosaur bone beds are clues about the size and strength of rivers dinosaurs had to wade through. Scientists compare the number of different types of dinosaurs from one location to find out about dinosaur habits and lifestyles. For example, if there were few predators and many animals that would have been their prey, it would show that the predatory dinosaurs had a quick metabolism and were probably warm-blooded.