What is the best and most reliable way to tell the age of dinosaur bones?
Paul Taylor: You don’t date the bones directly. Instead you make an estimate of the age of the rocks surrounding them. Often it isn’t even the surrounding rock, you can just test rocks that can be a correlated with them. The best rocks for dating fossils are igneous. Imagine you have a sedimentary rock with dinosaur bones in it and igneous rock above and below it. You may not be able to date the sedimentary rock directly but you can date the igneous rocks above and below. That’s how most fossil dating in general is done.
What is radiometric dating?
Taylor: Elements often have stable and unstable isotopes, which occur in known proportions. For example, when carbon is fixed inside the rocks, its isotopes are in a particular proportion. As the rock gets older, more of the unstable isotope disappears so you’re getting a higher proportion of stable isotopes and very little of the unstable. It’s like a clock. The rate is constant so the relative amount of unstable isotope that is left tells you the age. A good mineral to use as a measurement is glauconite in sedimentary rock, which contains the unstable isotope potassium-40.
Tell us about the discovery of soft tissue on bones. How important or even surprising was this?
Taylor: Some claims of soft tissues are quite controversial. However, what does quite often happen during fossilisation is permineralisation of soft tissues. Bacteria can coat the surface of soft tissue and precipitate calcium phosphate, which can replace the soft tissue. There are also imprints in the sediment of dinosaur skin.
Where is the best place to find dinosaur fossils in the world?
Taylor: There are several places. Wyoming and Utah in the USA have a lot, as does Alberta in Canada. Also, many dinosaurs have been found in China and Patagonia recently, and even the Isle of Wight is sometimes known as Dinosaur Island! Part of the reason is that fossils are most easily collected where the rocks are best exposed – it is much easier to find dinosaurs and other fossils in deserts than vegetated regions.
Dr Paul D. Taylor studies Bryozoan Research in the Department of Earth Sciences at the Natural History Museum