Resilience of infaunal ecosystems during the Early Triassic greenhouse Earth

Contrasting terrestrial and marine ecospace dynamics after the end-Triassic mass extinction event

Mass extinctions have fundamentally altered the structure of the biosphere throughout Earth's history. The ecological severity of mass extinctions is well studied in marine ecosystems by categorizing marine taxa into functional groups based on 'ecospace' approaches, but the ecological response of terrestrial ecosystems to mass extinctions is less well understood due to the lack of a comparable methodology. Here, we present a new terrestrial ecospace framework that categorizes fauna into functional groups as defined by tiering, motility and feeding traits. We applied the new terrestrial and traditional marine ecospace analyses to data from the Paleobiology Database across the end-Triassic mass extinction-a time of catastrophic global warming-to compare changes between the marine and terrestrial biospheres. We found that terrestrial functional groups experienced higher extinction severity, that taxonomic and functional richness are more tightly coupled in the terrestrial, and that the terrestrial realm continued to experience high ecological dissimilarity in the wake of the extinction. Although signals of extinction severity and ecological turnover are sensitive to the quality of the terrestrial fossil record, our findings suggest greater ecological pressure from the end-Triassic mass extinction on terrestrial ecosystems than marine ecosystems, contributing to more prolonged terrestrial ecological flux.

A Highly Diverse Olenekian Brachiopod Fauna from the Nanpanjiang Basin, South China, and Its Implications for the Early Triassic Biotic Recovery

As one of the predominant benthic organisms in the Palaeozoic, brachiopod was largely eliminated in the Permian-Triassic boundary mass extinction, and then highly diversified in the Middle Triassic. Since fossil data from the Early Triassic are rarely reported, the recovery patterns of Early Triassic brachiopods remain unclear. This study documents a well-preserved fauna that is the most diverse Olenekian brachiopod fauna so far (age constrained by conodont biostratigraphy) from the Datuguan section of ramp facies in South China. This fauna is composed of 14 species within nine genera, including six genera (Hirsutella, Sulcatinella, Paradoxothyris, Dioristella, Neoretzia and Isocrania) found in the Early Triassic for the first time and three new species, including Paradoxothyris flatus sp. nov., Hirsutella sulcata sp. nov. and Sulcatinella elongata sp. nov. The Datuguan fauna indicates that the diversity of Olenekian brachiopod fauna has been underestimated, which can be caused by a combination of reduced habitats (in geographic size and sedimentary type) compared with the end-Permian, great bed thickness making it difficult to find fossils and most species in the fauna having low abundance. Based on the faunal change in the Datuguan section and environmental changes in South China, it can be inferred that brachiopod recovery in the studied section occurred in the latest Spathian rather than the Smithian when the environment started to ameliorate. Global brachiopod data also indicates that the initial recovery of brachiopods happened in the Spathian, and many genera that widely occurred in the Middle or Late Triassic had originated in the Olenekian.

The stability and collapse of marine ecosystems during the Permian-Triassic mass extinction

The history of Earth's biodiversity is punctuated episodically by mass extinctions. These are characterized by major declines of taxon richness, but the accompanying ecological collapse has rarely been evaluated quantitatively. The Permian-Triassic mass extinction (PTME; ∼252 mya), as the greatest known extinction, permanently altered marine ecosystems and paved the way for the transition from Paleozoic to Mesozoic evolutionary faunas. Thus, the PTME offers a window into the relationship between taxon richness and ecological dynamics of ecosystems during a severe extinction. However, the accompanying ecological collapse through the PTME has not been evaluated in detail. Here, using food-web models and a marine paleocommunity dataset spanning the PTME, we show that after the first extinction phase, community stability decreased only slightly despite the loss of more than half of taxonomic diversity, while community stability significantly decreased in the second phase. Thus, taxonomic and ecological changes were unequivocally decoupled, with species richness declining severely ∼61 ka earlier than the collapse of marine ecosystem stability, implying that in major catastrophes, a biodiversity crash may be the harbinger of a more devastating ecosystem collapse.