A multiscale view of the Phanerozoic fossil record reveals the three major biotic transitions

The hypothesis of the Great Evolutionary Faunas is a foundational concept of macroevolutionary research postulating that three global mega-assemblages have dominated Phanerozoic oceans following abrupt biotic transitions. Empirical estimates of this large-scale pattern depend on several methodological decisions and are based on approaches unable to capture multiscale dynamics of the underlying Earth-Life System. Combining a multilayer network representation of fossil data with a multilevel clustering that eliminates the subjectivity inherent to distance-based approaches, we demonstrate that Phanerozoic oceans sequentially harbored four global benthic mega-assemblages. Shifts in dominance patterns among these global marine mega-assemblages were abrupt (end-Cambrian 494 Ma; end-Permian 252 Ma) or protracted (mid-Cretaceous 129 Ma), and represent the three major biotic transitions in Earth's history. Our findings suggest that gradual ecological changes associated with the Mesozoic Marine Revolution triggered a protracted biotic transition comparable in magnitude to the end-Permian transition initiated by the most severe biotic crisis of the past 500 million years. Overall, our study supports the notion that both long-term ecological changes and major geological events have played crucial roles in shaping the mega-assemblages that dominated Phanerozoic oceans. Rojas et al. present a new multi-scale model that reveals the three major biotic transitions of the Phanerozoic fossil record. This new model supports the hypothesis that both long-term ecological changes and major geological events played crucial roles in shaping ocean mega-assemblages through the Phanerozoic.

Automated summary

The study reveals the presence of four global benthic mega-assemblages in Phanerozoic oceans since the Cambrian period, with patterns of transition between these mega-assemblages being either abrupt or protracted, representing the three major biotic transitions in Earth's history. It also suggests that gradual ecological changes associated with the Mesozoic Marine Revolution triggered a protracted biotic transition comparable in magnitude to the end-Permian transition initiated by the most severe biotic crisis in the past 500 million years.