Low-Latitude Origins of the Four Phanerozoic Evolutionary Faunas

Sepkoski’s hypothesis of Three Great Evolutionary Faunas that dominated Phanerozoic oceans represents a foundational concept of macroevolutionary research. However, the hypothesis lacks spatial information and fails to recognize ecosystem changes in Mesozoic oceans. Using a multilayer network representation of fossil occurrences, we demonstrate that Phanerozoic oceans sequentially harbored four evolutionary faunas: Cambrian, Paleozoic, Mesozoic, and Cenozoic. These mega-assemblages all emerged at low latitudes and dispersed out of the tropics. The Paleozoic–Mesozoic transition was abrupt, coincident with the Permian mass extinction, whereas the Mesozoic–Cenozoic transition was protracted, concurrent with gradual ecological shifts posited by the Mesozoic Marine Revolution . These findings support the notion that long-term ecological changes, historical contingencies, and major geological events all have played crucial roles in shaping the evolutionary history of marine animals. One Sentence Summary Network analysis reveals that Phanerozoic oceans harbored four evolutionary faunas with variable tempo and underlying causes.