A COMPARATIVE ESTIMATE OF DIFFERENT BIODIVERSITY CURVES AND COMMENTS ON THE LINK BETWEEN ROCK AVAILABILITY AND BIODIVERSITY

Time-series estimates of Phanerozoic biodiversity may be criticized on the grounds that they use an inaccurate geochronology, are conducted at an inappropriate spatial scale, or inadequately address covariant changes in the availability of fossiliferous rock. Here, we present four different Phanerozoic marine diversity curves designed to comparatively assess each of the aforementioned concerns. We begin by contrasting Phanerozoic North American biodiversity when estimated using Macrostrat’s (macrostrat.org) new continuous-time-age model against the traditional binned-age model of the Paleobiology database (paleobiodb.org). We demonstrate that the overall pattern of ancient North American biodiversity is comparable between the two geochronologies, but that several distinct discrepancies emerge. Second, we compare both North American curves to a global biodiversity curve calculated from the entirety of the Paleobiology Database. We discuss two prominent periods when the curves diverge (i.e., the Ordovician and Jurassic), and comment on possible causes. Third, we present a variant North American biodiversity curve using a “sampled-in-bin” approach. All three North American biodiversity curves are broadly similar to time-series analyses of North American sedimentary rock. Of these, the “sampled-in-bin” curve is the most strongly correlated with rock availability, which is not unexpected given that stratigraphic hiatuses are the most likely cause of a Lazarus effect. North American rock availability and global biodiversity share less of a common signal. If North American strata are a suitable proxy for global rock availability, then the lack of a correlation between global biodiversity and quantities of North American rock suggests that global biodiversity is not strictly a function of stratigraphic preservation.