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.

Microfossil assemblages and geochemistry for interpreting the incidence of the Jenkyns Event (early Toarcian) in the south-eastern Iberian Palaeomargin (External Subbetic, SE Spain)

By studying the facies, geochemistry, and microfossil assemblages of the uppermost Pliensbachian and lower Toarcian of the Cueva del Agua section, I was able to appraise the impact of the Jenkyns Event in the eastern part of the South Iberian Palaeomargin (Western Tethys). Depleted oxygen conditions are envisaged for the Polymorphum–Serpentinum Zone boundary (lower Toarcian), represented by dark marls, precisely in a laminated interval. The decrease in the α diversity of foraminifera and ostracods, along with greater proportions of opportunists such as Lenticulina, Eoguttulina, and Cytherella just before the negative carbon isotopic excursion (CIE), would indicate a disturbance of the environmental conditions during the initial phase of the biotic crisis. The peak of the biotic crisis is characterized by an absence of trace fossils, increased organic matter content, an increased Mo∕Al ratio, and negative CIE and δ18O, as well as fewer specialist forms and more opportunists. This biotic crisis peak is related to oxygen-depleted conditions in the bottom waters and in the sediment pore water, while warming negatively affected microfauna – to the point of leaving a barren benthic horizon in the record. Recovery is evidenced by the occurrence of carbonate layers with hummocky cross-stratification and a decrease in organic matter content, the Mo∕Al ratio, and the trace fossil record. In terms of microfauna, the first phase of recovery shows highly abundant foraminifera, ostracods, and microgastropods, mainly opportunist forms. After the proliferation of opportunist forms, a second phase of recovery is marked by a progressive increase in α diversity.

Extinct and extant Pacific Trogossitidae and the evolution of Cleroidea (Coleoptera) after the Late Triassic biotic crisis

A new subgenus of Tenebroides, Polynesibroides subgen. nov., is established for six potentially extinct beetles, Tenebroides atiu, T. moorea, T. raivavae, T. rimatara, T. tubuai and T. mihiura spp. nov., described from the Cook, Austral and Society Islands based on subfossil fragments, and the extant T. tahiti sp. nov. from the island of Tahiti, Society Islands. Here we present the first detailed time-scaled phylogeny of the superfamily Cleroidea inferred from our four-gene dataset, including T. tahiti. Bayesian tip-dating, incorporating 17 fossils, estimated that Cleroidea appeared at the end of the Triassic (~210 Mya). The split of Biphyllidae + Byturidae + Phloiophilidae was reconstructed at ~204 Mya, followed by Early Jurassic separation of Trogossitidae (~200 Mya), Acanthocnemidae (~197 Mya), stem Cleridae–Thanerocleridae–Chaetosomatidae (~194 Mya), Peltidae, Lophocateridae, Decamerinae and the melyrid lineage (~191 Mya). Trogossitidae diversified by separation of Kolibacia (~136 Mya) in the Cretaceous, followed by parting Temnoscheila + Nemozoma and Airora + Tenebroides lineages (~113 Mya). Tenebroides radiated ~75 Mya and T. tahiti diverged from Panamanian taxa in the Middle Eocene (~40 Mya). Fourteen morphological characters of Pacific trogossitids were analysed. Parallelodera, including the Panamanian species, is nested within Tenebroides being sister to Polynesibroides. Therefore, Parallelodera is classified as a subgenus of Tenebroides. Tenebroides fairmairei is placed in the subgenus Parallelodera. A Neotropical origin for Parallelodera and Polynesibroides is inferred.

Linking Siberian Traps LIP Emplacement and End-Permian Mass Extinction: Evidence from Magnetic Stratigraphy of the Maymecha-Kotuy Volcanic Section

The Siberian Traps Large Igneous Provinces (LIP) emplacement is considered as one of possible triggers for the end-Permian global biotic crisis. However, relative timing of the onset of extinction and the main phase of the magmatic activity are not yet accurately constrained. We present the detailed paleomagnetic data for the thickest composite section of the Siberian Traps volcanics, located in the Maymecha-Kotuy region. The major part of the Maymecha-Kotuy section erupted in the beginning of Early Triassic period and postdate came the onset of the biotic crisis. However, the initial pulse of volcanic activity in this region took place at the end of the Permian period, and likely preceded the extinction event, being nearly coeval to the lowest part of tuff-lava sequence of Norilsk. The suggested correlation scheme of volcanic sections from different regions of the Siberian platform shows that explosive and extrusive events foregoing the onset of extinction can be identified in almost all regions of the Siberian Traps LIP. Finally, we estimate the total duration of magmatic activity in the Maymecha-Kotuy region as ~2 Myr and assume that this lasted after the termination of eruptions in other parts of the Siberian platform.