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

By Alexis Rojas, Joaquin Calatayud, Michal Kowalewski, Magnus Neuman, Martin Rosvall

Posted 06 Dec 2019
bioRxiv DOI: 10.1101/866186

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 are 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. This finding suggests that the mid-Cretaceous radiation of the so-called Modern evolutionary Fauna, concurrent with gradual ecological changes associated with the Mesozoic Marine Revolution, triggered a biotic transition comparably to the transition following the largest extinction event in the Phanerozoic. Overall, our study supports the notion that both long-term ecological changes and major geological events have played crucial roles in shaping mega-assemblages that dominated Phanerozoic oceans. ### Competing Interest Statement The authors have declared no competing interest.

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