This illustration shows what was probably a common scene during the late Jurassic Period, 150 million years ago - an allosaurus, the apex predator of the time, attacking a stegosaurus. These animals coexisted in the same part of North America so it is likely that they had a predator-prey relationship. The allosaurus is shown with wounds inflicted by the stegosaurus' tail spikes - its so-called thagomizer.