Dr David Norman, Director of the Sedgwick Museum of Earth Sciences, Cambridge University
David - I work on dinosaurs, but it's not geeky dinosaurs - it's the science of dinosaurs. This means that I look at things like their anatomy and their physiology. In order to do this, you really have to take the approach of a forensic scientist at the scene of a crime. What you have is a dead body and we have to some extent to try and bring it back to life. This can help you find out many interesting things about the history of life on earth.
Chris - The earth is very old: about 4500 million years! Where do dinosaurs fit into this?
David - The very first dinosaurs we know of were found in rocks that are 225 million years old during the late Triassic. The last ones (if you exclude birds, which are technically dinosaurs) lived about 65 million years ago. They fit into a period of time known as the Mesozoic.
Chris - When we watch films we ascribe to dinosaurs sounds, colours and ability to hear. Do we know if they could make sounds?
David - Yes we do, but only in a limited range of species; particularly those from North America known as duck-billed dinosaurs. These have very peculiar hollow crests on the top of their heads. It was thought at first that because they were connected to nasal passages they might be to do with an exaggerated sense of smell. That might have been the case, but acoustic analyses show that they are much more likely to be resonators. Indeed some are actually shaped like the tube of a trombone, which would certainly amplify sound. There are one or two skulls that have been very well preserved in three dimensions. CAT scan images of these skulls create a 3-D restoration. The internal cavities can be modelled and air can metaphorically be blown through them. Using this mechanism we see how it would have resonated. Obviously that's ignoring the fact that there would have been soft tissues too that would have modified the sound, but it at least gives us an idea. These types of dinosaurs make understandable sounds: that is understandable in terms of the biology of these creatures. The types of sound that they would make would have been very low frequencies, like a fog horn. These low frequencies can be transmitted across long distances and, unlike high frequencies, cannot be identified. These are animals that would have been preyed upon by things like Tyrannosaurus. By making a warning signal at a low frequency, the T-rex wouldn't know where the sound was coming from but all his mates would know that there was danger nearby.
Kat - What is your favourite dinosaur and why?
David - It would have to be a creature called the iguanodon. It's a very British dinosaur and it's also the reason that I'm a dinosaur expert. I started off as a dinosaur PhD student and was given the topic of this dinosaur. It was one of the first ever discovered in the 1820s and was studied by many people over the years. My research showed that there was quite a lot that we still didn't know about it.
Kat - Where in the UK is good for budding fossil hunters to start?
David - There actually aren't that many places. A good place is the Isle of Wight. The cliffs on the south coast yield dinosaur bones quite frequently. Please do it carefully though. If you find something, please take it to your local museum: it could be important.