CONICET | Buscador de Institutos y Recursos Humanos

The Mesozoic Marine Revolution (MMR) was a major evolutionary episode involving thelarge-scale restructuring of shallow-marine benthic communities and the rise to dominanceof the Modern Evolutionary Fauna. Although the majority of studies published on theMMR have been based on the body-fossil record, the ichnologic record yields valuableinsights into this evolutionary event, most notably regarding the degree of infaunalization,complexity of infaunal tiering structures, and predation intensity. The main groups ofbioturbators involved in the MMR were crustaceans, bivalves, echinoids, and ?worms,?whereas the most important bioeroders were sponges, gastropods, bivalves, echinoids, and?worms.?The Triassic, encapsulated between two major mass extinctions, can be regarded as settingthe stage for the MMR. The sparse ichnologic information available suggests that fullrecovery from the end-Permian mass extinction had taken place in equatorial carbonatesettings by the Middle Triassic, although ichnofaunas show limited infaunalization andrelatively simple tiering structures. However, a few key players, most notably some decapodcrustaceans, were already dominant in carbonate settings. Jurassic ichnofaunas reveala compositional turnover, signaling the rise to dominance of the Modern EvolutionaryFauna. This faunal turnover occurred by the Early Jurassic, as indicated by the taxonomiccomposition and increased diversity of bioturbation structures and the complexityof infaunal tiering. During the Cretaceous, a continuation of the trends establishedin the Jurassic was recorded. However, by the end of the Cretaceous, a modern-stylebenthic?pelagic coupling pattern was established, accompanied by an increase in globalichnodiversity. Rapid development of coccolithophores provided a new substrate (chalk)and an increasing flux of organic matter to the seafloor, enabling establishment of complextiering structures, unknown in older deposits. The degree of macrobioerosion indicatesan increasing participation of some players typical of modern communities. Paleogenebioturbation structures are similar to those of the late Mesozoic. Macrobioerosion stylesalso persisted across the Cretaceous?Paleogene boundary, albeit with an increased role forbioerosion by sponges and fishes later in the Paleogene. Predation pressures (drilling anddurophagy) increased during the Eocene. Ichnofaunas in shallow-marine sediments recordcontinued expansion of diversity during the Neogene, as well as more complex tieringstructures. Predation pressure continued to rise, involving primarily marine mammals.Although the MMR for the most part took place in shallow, fully marine settings, thetrace-fossil record also provides evidence for its expression in the deep sea and marginal-marine,brackish-water settings. Irregular echinoids and decapod crustaceans apparentlyhad migrated to the deep sea by the Late Jurassic, whereas most of the main players ofthe MMR in fully marine settings (e.g., decapod crustaceans, bivalves, worms) werealso dominant in brackish-water settings since the beginning of this major evolutionaryevent. Trace-fossil data indicate that infaunalization predates an increase of predationpressures by approximately 50 Myr, suggesting a complex set of feedback mechanismsbetween predation and infaunalization rather than simple cause and effect between thetwo. Turnover in ichnofaunal composition and the increased infaunalization that tookplace during the MMR strongly supports the ?bulldozing hypothesis? (the notion thatbiological disturbance increased through the Phanerozoic), indicating a dramatic rise inbioturbational sediment processing by elements of the Modern Evolutionary Fauna.