You might think that it is easy to put a skeleton together. But even if you do put it together correctly – and remember there may be many bones missing, so you may have to guess how many the animal had– you then have to think about how the animal used its skeleton.

If you are puzzled by this, then do this activity. Raise one arm above your head. It's easy to do because your arm fits into a socket that lets it move about.

Now suppose someone comes across your skeleton and who has no knowledge of people. He has an arm, but he does not know how you use it or how you held it. So he decides that you held your arms above your head..

Now try this other activity. Bend over and touch your toes. Another scientist is working on another human skeleton in a separate laboratory. He sees that your legs will bend around because you have a ball and socket joint in your hips. So he decides that you walked on your legs and your hands and you walked about bent double, much like many other animals..

Both of these scientists have put the skeletons back together correctly, but each has decided differently how humans moved about. One thinks humans held their arms above their heads as they walked. Another decides they walked on all fours. .

You know that both are wrong. How stupid, you might think. But this is exactly the problem scientists have had with dinosaurs. How did they move about? How did they hold their heads? There are no dinosaurs round to tell them. So, with the best will in the world, they can get it wrong..

And they did. T. rex, for example, was reconstructed in a standing upright pose for a century. You see this in many pictures. But more recently scientists have begun to think it held its neck level with its tail, so its head stuck out forwards, rather than being held high. But looking at ourselves, you can see how easy it is to get things wrong when you don't have much to go on.
This is what makes finding out about dinosaurs even more interesting. It is also likely that we shall, in time, learn other things that will change our views on how dinosaurs moved, ate and lived. Perhaps you will be the scientist to find out!