IS THE MESO-CENOZOIC MARINE REVOLUTION AN ANALOG FOR BIODIVERSIFICATION DURING THE LATE NEOPROTEROZOIC?

We suggest that the quantity and, especially, quality of food were critical to marine biodiversification. During the Meso-Cenozoic, rising oxygen levels, continued nutrient input from land (as reflected by increases of the Sr isotope curve), and increasing rates of bioturbation (and nutrient recycling) all enhanced nutrient availability, increasing the macro- and micro- (trace element) nutrient content of phytoplankton. Consequently, marine metazoans had to expend less energy to “burn off” (respire) excess carbon to obtain inorganic nutrients necessary for growth, leaving more energy available for reproduction and, potentially, micro- and macroevolution. By contrast, the absence of well-developed terrestrial floras and low bioturbation rates may have limited nutrient availability during the early-to-middle Paleozoic. Diversification of early-to-middle Paleozoic metazoans would have been limited by having to expend energy to “burn off” the excess carbon of more nutrient-poor phytoplankton. Limited nutrient availability may have delayed the appearance of more advanced and “energetic” taxa such as advanced carnivores until the Permo-Carboniferous, when widespread orogeny, falling sea level, the spread of forests and greater weathering rates, enhanced ocean circulation, oxygenation, and upwelling all combined to increase nutrient availability in the oceans. Given the apparent role of nutrient availability in biodiversification during the Phanerozoic and the sharp increase of Sr ratios during the Neoproterozoic, we ask: 1) Is the steep rise of the fossil record of biodiversity during the Meso-Cenozoic more real than apparent (despite possible preservational and sample bias)? 2) Is the steep rise of biodiversity during the Meso-Cenozoic an analog for initial biodiversification during the late Neoproterozoic (despite differences in genetic constraints)? 3) Are intervals of (apparent) biodiversification prolonged “trophic cascades” of community reorganization?