Abstract: Palaeodiversity curves are constructed from counts of fossils collected at outcrop and thus potentially biased by variation in the rock record, specifically by the amount of sedimentary rock representative of different time intervals that has been preserved at outcrop. To investigate how much of a problem this poses we have compiled a high-resolution record of marine rock outcrop area in Western Europe for the Phanerozoic and use this to generate a model that predicts the sampled diversity curve. We find that we can predict with high accuracy the variance of the marine genus diversity curve (itself dominated by European taxa) from rock outcrop data and a three-step model of diversity that tracks supercontinent fragmentation, coalescence and fragmentation. The size and position of two of the five major mass extinction spikes are largely predicted by rock outcrop data. We conclude that the long-term trends in taxonomic diversity and the end-Cretaceous extinction are not the result of rock area bias, but cannot rule out that rock outcrop area bias explains many of the short-term rises and falls in sampled diversity that palaeontologists have previously sought to explain biologically.