PALEOGEOGRAPHIC BOUNDARY CONDITIONS FOR PHANEROZOIC BIODIVERSITY ANALYSIS: A QUANTITATIVE FRAMEWORK

The geographic arrangement of continental and oceanic lithosphere exerts a first-order control on the Earth’s surface environment by influencing the circulation structure of the ocean-atmosphere system, the connectivity of the biosphere, and planetary albedo. It has consequently been hypothesized, beginning with Valentine and Moores (1970), that long-term patterns of global and regional biodiversity during the Phanerozoic reflect evolving paleogeographic boundary conditions and associated climatic and eustatic effects. Testing the explanatory power of this hypothesis requires quantitative data on the distribution and taxonomic classification of fossil occurrences as well as data on the shifting global paleogeographic landscape. Because the former have been readily available via the Paleobiology Database (http://paleobiodb.org) for almost two decades, most studies to date have focused on measuring the paleogeographic dispersion of fossil occurrences (e.g., maximum great circle distances or convex hull relationships) and on estimating global biogeographic patterns, such as latitudinal diversity gradients, in the fossil record. Here we combine newly developed cyberinfrastructure provided by GPlates (www.gplates.org) with the geographic analysis capabilities of PostGIS to quantitatively summarize global physical paleogeography and its relationship to PaleoBioDB fossil occurrences and biodiversity at one million year time increments for the past 550 million years. As predicted by Valentine and Moores, there is evidence for a positive relationship between continental dispersion and between-plate biodiversity during the Phanerozoic. This relationship is modulated by the supercontinental coalescence and breakup cycle, which manifests in all quantitative expressions of Phanerozoic paleogeography, most notably as lows in continental fragmentation during the Triassic and Neogene and highs in fragmentation during the early Paleozoic and Cretaceous. Although paleogeographic reconstructions often utilize paleontological data, particularly in time intervals predating the oldest surviving seafloor, the ability to readily analyze global physical paleogeography provides an important framework for generating null biological models and for testing paleobiological hypotheses.