Paleoecologic Megatrends in Marine Metazoa

Since their appearance in the Neoproterozoic, marine metazoan ecosystems have increased in ecological diversity, complexity, energy use, motility, predation, infaunality, and biological disturbance. A common theme is an increase in organismal control over internal physiology and the external environment. Often, these changes have been examined in the context of discrete events (e.g., the Cambrian Explosion, Mesozoic Marine Revolution), but they may represent linked, ongoing megatrends. This review examines changes in ecological composition in the context of changes in taxonomic composition, as represented by a more detailed version of Sepkoski's evolutionary fauna analysis. Ecological change occurred during major radiations and extinctions, as well as between them. Due to its ecological selectivity, the Permian-Triassic extinction had particularly significant ecological effects on the biota. Recoveries from mass extinctions may be important episodes of ecological change. Further research could help elucidate the fundamental causes of long-term ecological change, including any role played by the environment.