Back in the mists of prehistory, when I was eight, dinosaur films followed a set pattern. The dinosaurs themselves would be cheerfully unpalaeontological; women would wear improbable outfits; volcanoes would explode. Then, in 1993, courtesy of Steven Spielberg, came a sea-change. Jurassic Park was that cinematic rarity: a science fiction film that succeeded in influencing the science it was fictionalising.