A special showing of this film in response to numerous requests from younger viewers.
For 150 years, since the first dinosaur was discovered, more and more fossils have been found.
Today palaeontologists are looking at these extraordinary creatures and asking: How could they possibly have worked? Where did they come from? Why did they become extinct?
To answer these questions Horizon followed two scientists across the plains of Utah in the United States.

"Fascinating trail across the plains of Utah to find out how these ungainly reptiles managed to dominate the earth." (Sunday Telegraph)