Permian-Triassic Mass Extinction Research Articles

Morphological selectivity of the Permian-Triassic ammonoid mass extinction

Abstract Ammonoids suffered a diversity bottleneck during the Permian-Triassic mass extinction (PTME) and experienced a rapid diversification in the Early Triassic. However, the kinds of ammonoids that were more likely to survive the PTME and that fueled subsequent diversification are still poorly known. We compiled a comprehensive morphological data set and used the nonmetric multidimensional scaling method to reveal the impact of the PTME on the morphological selectivity of ammonoids. Our results show that postextinction taxa occupied a quite different morphospace when compared with the pre-extinction assemblages. The survivors were mainly smooth and weakly ornamented forms, while the late Permian species were dominated by coarsely ornamented forms. Contrary to previously recognized nonselective patterns, these results suggest a morphological selectivity of the Permian-Triassic crisis. Newcomers in the Griesbachian were mainly compressed and smooth forms. This morphological shift from the coarsely ornamented ammonoids dominating the Changhsingian to the smooth ammonoids dominating the Griesbachian possibly suggests an ecological turnover of ammonoids during the PTME.

New data on the Triassic temnospondyls from the Karoo rift basins of Tanzania and Zambia

Temnospondyl specimens collected recently in the Middle-?Late Triassic of the Ruhuhu (Tanzania) and Luangwa (Zambia) rift basins are described and figured. They are attributed to cf. Cherninia megarhina (Chernin & Cosgriff, 1975), Mastodonsauroidea indet., Stereospondyli indet., and cf. Stereospondyli, as well as intercentra of small adult individual(s) which may belong to a new taxon. Although fragmentary, this new material allows taxonomic updates to the Triassic temnospondyl assemblages of Tanzania and Zambia and documents an interesting phylogenetic and ecological diversity. For example, among the Triassic mastodonsauroids of Zambia, Cherninia megarhina coexisted with Stanocephalosaurus pronus (Howie, 1970) in nonmarine environments. Similar to that of the South African Karoo Basin, these temnospondyl assemblages also illustrate the rapid recovery of the group after the Permian-Triassic mass extinction and contribute to a better understanding of the impact of this extinction on the tetrapod faunas of southern Pangea.

Biotic response to environmental shift during the Permian-Triassic transition: Assessment from organic geochemical proxies and palynomorphs in terrestrial sediments from Raniganj Sub-basin, India

The Permian-Triassic (P/T) mass extinction qualifies as the severest biotic perturbation in the history of our planet. Biomarkers, stable isotopes and palynomorphs are excellent proxies offering glimpses into palaeobiota and past ecosystems. These were investigated from coal-bearing upper Permian (Raniganj Formation) and Lower Triassic (Panchet Formation) Gondwana sediments recovered from the Raniganj Sub-basin, eastern India. The geochemical and palaeobotanical data suggest a shift in the terrestrial vegetation during the Early Triassic. A distinct change occurs from high abundance of n-C23 and n-C25 alkanes and higher CPI values in the upper Permian sediments to predominantly n-C27 and n-C29 alkanes along with relatively lower CPI values in the Lower Triassic. A sharp decline of the diterpenoid compounds and Glossopteridales pollens with a concomitant rise in lycopsid spores in the Lower Triassic sediments reflects the waning of a gymnosperm-dominated mire and onset of a stressed environment. Unlike the Glossopteridales, the Coniferales appear to be a resilient floral group with several new genera adapting to the growing arid conditions in the Early Triassic. The microbial community also responded to the contemporaneous ecosystem shift, with higher concentration of C27 sterane relative to C29 sterane in Lower Triassic sediments indicating proliferation of algal phytoplankton. The decreasing moretane/hopane (M/H) suggests that the soil bacteria were adversely affected plausibly due to enhanced soil erosion at the early part of the Triassic. A marked shift in the bulk isotopic composition (δ13Corg) from higher values in the upper Permian sediments (˗21.0 to ˗24.1‰) to lower values in the Lower Triassic sediments (˗21.2 to ˗32.5‰) is diagnostic of a vegetation changeover as a result of environmental deterioration. This is the first integrated study using molecular organic geochemical proxies and palynology from terrestrial Gondwana sediments in the Indian subcontinent, designed to investigate the pattern of floral and microbial restructuring as a result of an environmental shift during the Permian-Triassic transition.

Niche partitioning shaped herbivore macroevolution through the early Mesozoic

The Triassic (252–201 Ma) marks a major punctuation in Earth history, when ecosystems rebuilt themselves following the devastating Permian-Triassic mass extinction. Herbivory evolved independently several times as ecosystems comprising diverse assemblages of therapsids, parareptiles and archosauromorphs rose and fell, leading to a world dominated by dinosaurs. It was assumed that dinosaurs prevailed either through long-term competitive replacement of the incumbent clades or rapidly and opportunistically following one or more extinction events. Here we use functional morphology and ecology to explore herbivore morphospace through the Triassic and Early Jurassic. We identify five main herbivore guilds (ingestion generalists, prehension specialists, durophagous specialists, shearing pulpers, and heavy oral processors), and find that herbivore clades generally avoided competition by almost exclusively occupying different guilds. Major ecosystem remodelling was triggered multiple times by external environmental challenges, and previously dominant herbivores were marginalised by newly emerging forms. Dinosaur dominance was a mix of opportunity following disaster, combined with competitive advantage in their new world.

Climate and biotic evolution during the Permian-Triassic transition in the temperate Northern Hemisphere, Kuznetsk Basin, Siberia, Russia

The Siberian Traps volcanism is widely considered the main cause of the end-Permian mass extinction, the greatest biological crisis in the Earth history. While the extinction is interpreted as catastrophic and sudden with estimates of duration of approximately 35–40 thousand years from marine strata in South China, various lines of evidence have emerged for a more complex, prolonged, and diachronous extinction pattern. We present here the results of a multidisciplinary study of the Permian-Triassic continental transition in the Kuznetsk Basin, Russia. The region is proximal to the Siberian Traps LIP and the detrimental effects of the flood basalt volcanism in the Kuznetsk Basin may have been of similar scale as in the main area of the Siberian Traps distribution (Tunguska and Taymyr regions). Whereas earlier work has placed the Permian-Triassic boundary position between the coal-bearing Tailugan Formation and the volcanoclastic Maltsev Formation, here we revised the traditional model using three independent methods: radioisotopic CA-IDTIMS U-Pb zircon ages, δ13Corg isotope values and paleomagnetic proxies. The regional extinction of the humid-dominated forest flora (cordaites) and the aridity-induced biotic turnover in the Kuznetsk Basin occurred 820 kyr earlier than the end-Permian extinction event recorded in South China at 251.94 Ma. The biota in Kuznetsk Basin at the turnover subsequently diversified (with some exceptions) across the Permian-Triassic transition.By compiling a large taxonomic database, we find that marine and terrestrial biotic diversity in Siberia progressively increased from the beginning of the Permian up to the middle Roadian (early Guadalupian global glacial event). After that time, the diversity at the species and generic level progressively and slowly declined towards the aforementioned latest Changhsingian (252.76 Ma) biotic turnover. Starting from this time, the biota rapidly diversified in the latest Changhsingian and Early-Middle Triassic. We suggest that the Permian-Triassic mass extinction mostly occurred in the tropics and subtropics due to the strong climatic warming, which was relatively low in late Changhsingian and gradually but quickly extends in the latest Changhsingian to an abnormally high temperature and extremely low oxygenated water in the oceans that was deadly for most marine animals. The warm climate shift poleward during Permian-Triassic transition in the middle-high latitudes caused the replacement (turnover) of the humid-related biotas by the dry climate-related and more diverse communities, which continued to expand throughout the Triassic in both marine and terrestrial habitats. The pattern of the Permian-Triassic event in both marine and terrestrial habitats was more intricate in terms of extinction, turnover, and diversity of biota within the different climatic zones and environmental habitats than has been generally considered.

Transient Permian-Triassic euxinia in the southern Panthalassa deep ocean

Both the duration and severity of deep-water anoxic conditions across the Permian-Triassic mass extinction (PTME) are controversial. Panthalassa Ocean circulation models yield varying results, ranging from a well-ventilated deep ocean to rapidly developing northern-latitude, but not southern-latitude, anoxia in response to Siberian Traps–driven global warming. To address this uncertainty, we examined a southern-paleolatitude pelagic record. Trace metal and pyrite framboid data suggest bottom-water euxinic conditions developed in the southern Panthalassa Ocean at the PTME, coincident with enhanced volcanic activity indicated by Hg geochemistry. While a global ocean euxinic event at the PTME placed extraordinary stress on marine life, southern surface waters appear to have recovered more quickly as radiolarian populations returned several million years before they did in northern Panthalassa.

The link between exceptional fossil preservation and palaeo‐redox conditions in the Middle Triassic Luoping Biota from South China

The Luoping Biota represents of the recovery of marine ecosystems after the Permian–Triassic Mass Extinction. To better understand the palaeoenvironmental background of the Luoping Biota, sedimentary analysis and multi‐geochemical proxies (Mo, U, V, V/Cr, MoEF, UEF, and VEF) were assessed in Member II of the Middle Triassic Guanling Formation of the Xiangdongpo section in Luoping County, Yunnan Province. According to the facies characteristics and redox‐sensitive elemental proxies, in combination with macrofossil and bioturbation evidence, five intervals (I, II, III, IV, and V) were recognized. The exceptional preservation of the fossils is related to two anoxic intervals (II and IV) sandwiched by three suboxic intervals (I, III, and V). Based on this study and regional correlation, it is concluded that anoxia in the water‐column increased the preservation potential of macrofauna fossils and inhibited the survival of trace‐making organisms. In addition, microbial mats could produce local anoxic and restricted micro‐environments, preventing the disarticulation of the carcasses by water turbulence. Therefore, we demonstrate that anoxic conditions played a key role in the exceptional fossil preservation of the Luoping Biota.

Biostratigraphic significance and geometric morphometrics of Euestheria gutta (Crustacea: Branchiopoda: Spinicaudata): An index fossil of continental Permian–Triassic transitional beds

The Permian–Triassic mass extinction was the largest biotic extinction event in the Phanerozoic and affected both marine and continental life. Marine Permian–Triassic transitional sequences can be correlated in many regions, but this has proved difficult for continental successions. A growing number of studies show that spinicaudatans are some of the most common fossils in continental strata and can be used as index fossils for continental stratigraphic division and correlation. Here we document the morphology and biostratigraphic significance of Euestheria gutta based on well‐preserved fossils from southwestern China. It shows strong intraspecific morphological variation, while the most important feature is the strongly convex larval valve and significant finely pitted to weakly reticulated ornamentation on the growth bands. Evidence from palaeobotany, charcoal, and organic carbon isotopes indicated that the continental mass extinction in southwestern China was marked by the catastrophic loss of tropical rainforest vegetation, enhanced wildfire and a negative carbon isotope excursion (CIE) during the P–Tr transition. Meanwhile, abundant E. gutta first appeared at the onset of the negative CIE and just above the horizon of the loss of macroflora. Based on the global geographic distribution of E. gutta and temporal correlation, we conclude that this species existed from the latest Permian to the earliest Triassic, and the occurrence of E. gutta could be used as an index fossil of the continental mass extinction interval or P–Tr transitional beds.

A new acritarch spike of Leiosphaeridia dessicata comb. nov. emend. from the Upper Permian and Lower Triassic sequence of India (Pranhita-Godavari Basin): Its origin and palaeoecological significance

The Permian–Triassic Mass Extinction (PTME) event was the largest bio crisis to date, adversely affecting life on land and sea. The PTME event is evidenced in India by the destruction of glossopterids with immense loss of peat-forming vegetation, its replacement by stress-tolerant lycopsids, Lilliput Effect and the presence of numerous acritarchs and abnormal pollen grains. However, there are no reports for algal or acritarch spikes. We document, for the first time, an acritarch spike in the Indian subcontinent from the uppermost Permian to Lower Triassic sequence from the Pranhita–Godavari (P-G) Basin. Lithostratigraphically, the late Permian and Early Triassic aged deposits in the P-G basin are designated as the Kamthi Formation. The formation has a very rich and diverse assemblage of pollen grains, spores and acritarchs. Based on a palynological study, an abundance of Leiosphaeridia dessicata comb. nov. emend. has been identified from sediment samples from the two bore cores (MCP-7 and MCP-8) of the Chintalapudi sub-basin, P-G basin. The acritarch appearance and abundance occurred in synchronization with the floral shift. The acritarch appears along with the stress-tolerant lycopsid spores in the uppermost Permian assemblage and increases in accordance with lycopsid spores in the Lower Triassic assemblages.The morphology of Leiosphaeridia dessicata comb. nov. emend. relates its close affinity with an extant marine algal cyst of Acetabularia acetabulum. Moreover, the presence of gammacerane and methylate chromans in the host sediment indicates the hypersaline water column during the deposition. Thus, based on the presence of marine and hypersaline biomarkers and affinity of L. dessicata comb. nov. emend. with marine alga (probably Prasinophyceae or Chlorophyceae) infer that the deposition during the uppermost Permian and Lower Triassic occurred under shallow marine conditions, contradictory to the earlier belief that Indian Upper Permian and Triassic deposits are entirely terrestrial. The possible marine incursion in the P-G basin may have occurred from the eastern continental margin along western Australia or through a passage between the Indian southern margin and the west margin of Antarctica.

Metal-induced stress in survivor plants following the end-Permian collapse of land ecosystems

AbstractTeratological spores and pollen are widespread in sediments that record the Permian-Triassic mass extinction. The malformations are thought to be the result of extreme environmental conditions at that time, but the mutagenic agents and the precise timing of the events remain unclear. We examined the abundance of teratological sporomorphs and metal concentrations in a Permian-Triassic tropical peatland succession of southwestern China. We find a significant peak of spore tetrads of lycopsid plants (as much as 19% of all sporomorphs) coeval with increases in Cu and Hg concentrations above the main terrestrial extinction interval, which marks the loss of Permian Gigantopteris forests, increased wildfire activity, and the disappearance of coal beds. Thus, in tropical peatlands, mutagenesis affected only surviving plants. Mutagenesis was likely caused by metal toxicity, linked to increased Hg and Cu loading, but was not itself a direct cause of the terrestrial crisis.

A Hiatus Obscures the Early Evolution of Modern Lineages of Bony Fishes

About half of all vertebrate species today are ray-finned fishes (Actinopterygii), and nearly all of them belong to the Neopterygii (modern ray-fins). The oldest unequivocal neopterygian fossils are known from the Early Triassic. They appear during a time when global fish faunas consisted of mostly cosmopolitan taxa, and contemporary bony fishes belonged mainly to non-neopterygian (“paleopterygian”) lineages. In the Middle Triassic (Pelsonian substage and later), less than 10 myrs (million years) after the Permian-Triassic boundary mass extinction event (PTBME), neopterygians were already species-rich and trophically diverse, and bony fish faunas were more regionally differentiated compared to the Early Triassic. Still little is known about the early evolution of neopterygians leading up to this first diversity peak. A major factor limiting our understanding of this “Triassic revolution” is an interval marked by a very poor fossil record, overlapping with the Spathian (late Olenekian, Early Triassic), Aegean (Early Anisian, Middle Triassic), and Bithynian (early Middle Anisian) substages. Here, I review the fossil record of Early and Middle Triassic marine bony fishes (Actinistia and Actinopterygii) at the substage-level in order to evaluate the impact of this hiatus–named herein the Spathian–Bithynian gap (SBG)–on our understanding of their diversification after the largest mass extinction event of the past. I propose three hypotheses: 1) the SSBE hypothesis, suggesting that most of the Middle Triassic diversity appeared in the aftermath of the Smithian-Spathian boundary extinction (SSBE; ∼2 myrs after the PTBME), 2) the Pelsonian explosion hypothesis, which states that most of the Middle Triassic ichthyodiversity is the result of a radiation event in the Pelsonian, and 3) the gradual replacement hypothesis, i.e. that the faunal turnover during the SBG was steady and bony fishes were not affected by extinction events subsequent to the PTBME. Based on current knowledge, hypothesis three is favored herein, but further studies are necessary to test alternative hypotheses. In light of the SBG, claims of a protracted diversification of bony fishes after the PTBME should be treated with caution.

A diverse gastropod fauna from the shallow marine carbonate platform of the Yangou section (south China) in the immediate aftermath of the Permian–Triassic mass extinction

The Permian–Triassic mass extinction (PTME), the most devastating extinction event in Phanerozoic history, has witnessed the demise of almost 80% of marine gastropod genera. Despite the vast scale of the extinction event, the recovery of some groups of marine gastropods has been curiously fast, contrasting with the delayed recovery of many other marine clades. Understanding the rapid recovery of gastropods after the PTME represents a major palaeobiological conundrum, since oxygen‐dependent taxa are expected to have been severely impacted by anoxic oceanic conditions of the PTME. The controversial microbialite refuge hypothesis has been proposed as a potential explanation of this pattern, arguing that marine invertebrates were associated with oxygen‐producing microbial mats during the PTME, which provided a suitable microhabitat for survival within hostile anoxic conditions. To better understand the dynamics of gastropod recovery after the PTME, we studied a gastropod fauna collected from the basal Daye Formation (earliest Triassic) at the Yangou section in Leping County, Jiangxi Province, south China, allowing us to capture a snapshot of the marine fauna immediately after the PTME. Altogether, 13 microgastropod species belonging to 12 genera were recorded, representing the most diverse Induan (earliest Triassic) gastropod fauna in the world known to date. The fact that the Yangou assemblage, along with the second most diverse Griesbachian gastropod fauna from the Wadi Wasit section in Oman, is not associated with microbial buildups implies that microbial mats probably did not play a key role as refuges for marine invertebrates during the PTME. On the other hand, the Yangou fauna suggests that non‐anoxic shallow lagoon systems were more likely to have acted as refuges for marine invertebrates during the PTME.

Stromatolites from the Lower Triassic Virgin Limestone at Blue Diamond, NV USA: The role of dysoxia, enhanced calcification and nutrient availability in the growth of post-extinction microbialites

Abstract Microbialites undergo a well – documented resurgence following the Permian – Triassic mass extinction. This comeback has been attributed to several causes, including the emptying of Early Triassic ecosystems by the severity of the extinction, a decline in burrowing activity and intensity, and the unusual chemistry of Early Triassic oceans. A laterally – continuous stromatolite horizon found within the Lower Triassic Virgin Limestone was examined at the Blue Diamond, NV U.S.A. locality in order to determine the factors that led to growth of the stromatolites, and by extension, the environmental conditions that led to the formation of widespread microbialites in the aftermath of the Permian-Triassic mass extinction. The Virgin Limestone at the study locality consists of ~6 m – thick cycles of shale and siltstone that pass upwards into bioturbated lime mudstone, and are capped by oolitic packstone or grainstone. Each ~6 m – thick cycle represents a rapid sea level rise that led to the deposition of fine – grained clastics below storm wave base, followed by deposition of coarsening – upwards carbonates that were deposited in progressively shallower environments. Analysis of redox-sensitive trace metals (U. V and Mo) from the shale and siltstone interbeds indicate that the fine – grained clastics were deposited under dysoxic waters, however, extensive bioturbation and macrofossils from the carbonate units indicates better aeration of shallower settings. The stromatolites occur within a single, laterally extensive horizon, and 4 distinct stromatolite morphologies are observed along a 3 km long transect, including: 1) aggregates of high-relief hemispherical domes and columnar stromatolites with well-developed laminae that are up to 0.75 m thick; 2) lozenge-shaped aggregates of intergrown columnar stromatolites with dimpled top surfaces; 3) isolated hemispheroids; and, 4) meandering ridges of intergrown domes that are small, low – relief (usually

Disaster microconchids from the uppermost Permian and Lower Triassic lacustrine strata of the Cis-Urals and the Tunguska and Kuznetsk basins (Russia)

AbstractWe describe aggregative microconchid (Lophophorata) tubes from the uppermost Permian (upper Changhsingian) and Lower Triassic (Olenekian) lacustrine and fluvial strata of the Tunguska and Kuznetsk basins and the southern Cis-Urals, Russia. These attach to clam shrimp carapaces, bivalve shells, terrestrial plant fragments and a horseshoe crab head shield, and also form their own monospecific agglomerations. Planispiral tubes of a wide size range (0.1–2.5 mm) create dense settlements on these firm substrates, which likely comprise multiple generations of the same species. These finds confirm that this extinct lophophorate group was inhabiting non-marine continental basins during latest Permian and earliest Triassic time, when they were major suspension feeders in such limnic ecosystems. Microconchids dispersed extensively and rapidly in the aftermath of the Permian–Triassic mass extinction into both marine and continental basins at low and moderately high latitudes, which were notably different in salinity, temperature, depth and redox conditions. This confirms that small lightly calcified microconchids were a genuine disaster eurytopic group, whose expansion may have been promoted by low predator pressure and low competition for substrate.

Archosauriform footprints in the Lower Triassic of Western Alps and their role in understanding the effects of the Permian-Triassic hyperthermal.

The most accepted killing model for the Permian-Triassic mass extinction (PTME) postulates that massive volcanic eruption (i.e., the Siberian Traps Large Igneous Province) led to geologically rapid global warming, acid rain and ocean anoxia. On land, habitable zones were drastically reduced, due to the combined effects of heating, drought and acid rains. This hyperthermal had severe effects also on the paleobiogeography of several groups of organisms. Among those, the tetrapods, whose geographical distribution across the end-Permian mass extinction (EPME) was the subject of controversy in a number of recent papers. We here describe and interpret a new Early Triassic (?Olenekian) archosauriform track assemblage from the Gardetta Plateau (Briançonnais, Western Alps, Italy) which, at the Permian-Triassic boundary, was placed at about 11° North. The tracks, both arranged in trackways and documented by single, well-preserved imprints, are assigned to Isochirotherium gardettensis ichnosp. nov., and are here interpreted as produced by a non-archosaurian archosauriform (erytrosuchid?) trackmaker. This new discovery provides further evidence for the presence of archosauriformes at low latitudes during the Early Triassic epoch, supporting a model in which the PTME did not completely vacate low-latitude lands from tetrapods that therefore would have been able to cope with the extreme hot temperatures of Pangaea mainland.

New Thylacocephala (Crustacea) assemblage from the Spathian (Lower Triassic) of Majiashan (Chaohu, Anhui Province, South China)

AbstractHere we report and describe a new assemblage of Thylacocephala (Crustacea) from the late Spathian (Early Triassic) of Chaohu, Anhui Province, South China. The assemblage consists of at least three species from different genera: the small-sized Microcaris rectilineatus n. sp. appears the most abundant, while the large-sized Ankitokazocaris sp. and Diplacanthocaris chaohuensis n. gen. n. sp. are rare. A morphometric analysis of the carapace outline separates Diplacanthocaris chaohuensis n. gen. n. sp. from other genera. Along with Ankitokazocaris chaohuensis Ji et al., 2017 and Kitakamicaris sp. from the horizon 28 m above this assemblage, four different genera of Thylacocephala occur in the Chaohu Fauna. With additional materials reported from Japan and North America, the Early Triassic is now known as the period when Thylacocephala reached their highest diversity and widest geographical distribution. Thylacocephala quickly diversified shortly after the Permian–Triassic mass extinction, probably because of their ability to survive in a relatively low-oxygen environment. Thylacocephalan fossils from Chaohu are found in dense concentrations, suggesting they might have constituted a food source for the fishes and marine reptiles in the Chaohu Fauna.UUID: http://zoobank.org/b24e82a7-ea9a-49dc-9c6c-8ad8262db276

Permian–Triassic mass extinction pulses driven by major marine carbon cycle perturbations

The Permian/Triassic boundary approximately 251.9 million years ago marked the most severe environmental crisis identified in the geological record, which dictated the onwards course for the evolution of life. Magmatism from Siberian Traps is thought to have played an important role, but the causational trigger and its feedbacks are yet to be fully understood. Here we present a new boron-isotope-derived seawater pH record from fossil brachiopod shells deposited on the Tethys shelf that demonstrates a substantial decline in seawater pH coeval with the onset of the mass extinction in the latest Permian. Combined with carbon isotope data, our results are integrated in a geochemical model that resolves the carbon cycle dynamics as well as the ocean redox conditions and nitrogen isotope turnover. We find that the initial ocean acidification was intimately linked to a large pulse of carbon degassing from the Siberian sill intrusions. We unravel the consequences of the greenhouse effect on the marine environment, and show how elevated sea surface temperatures, export production and nutrient input driven by increased rates of chemical weathering gave rise to widespread deoxygenation and sporadic sulfide poisoning of the oceans in the earliest Triassic. Our findings enable us to assemble a consistent biogeochemical reconstruction of the mechanisms that resulted in the largest Phanerozoic mass extinction. The end-Permian mass extinction was linked with ocean acidification due to carbon degassing associated with Siberian Trap emplacement, according to boron isotopes from fossil shells and reconstruction of the carbon cycle.

Size variations in foraminifers from the early Permian to the Late Triassic: implications for the Guadalupian–Lopingian and the Permian–Triassic mass extinctions

AbstractThe final 10 Myr of the Paleozoic saw two of the biggest biological crises in Earth history: the middlePermian extinction (often termed the Guadalupian–Lopingian extinction [GLE]) that was followed 7–8 Myr later by Earth's most catastrophic loss of diversity, the Permian–Triassic mass extinction (PTME). These crises are not only manifest as sharp decreases in biodiversity and—particularly for the PTME—total ecosystem collapse, but they also drove major changes in biological morphological characteristics such as the Lilliput effect. The evolution of test size among different clades of foraminifera during these two extinction events has been less studied. We analyzed a global database of foraminiferal test size (volume) including 20,226 specimens in 464 genera, 98 families, and 9 suborders from 632 publications. Our analyses reveal significant reductions in foraminiferal mean test size across the Guadalupian/Lopingian boundary (GLB) and the Permian/Triassic boundary (PTB), from 8.89 to 7.60 log10μm3(lg μm3) and from 7.25 to 5.82 lg μm3, respectively. The decline in test size across the GLB is a function of preferential extinction of genera exhibiting gigantism such as fusulinoidean fusulinids. Other clades show little change in size across the GLB. In contrast, all Lopingian suborders in our analysis (Fusulinina, Lagenina, Miliolina, and Textulariina) experienced a significant decrease in test size across the PTB, mainly due to size-biased extinction and within-lineage change. The PTME was clearly a major catastrophe that affected many groups simultaneously, and the GLE was more selective, perhaps hinting at a subtler, less extreme driver than the later PTME.

Toward an understanding of cosmopolitanism in deep time: a case study of ammonoids from the middle Permian to the Middle Triassic

AbstractCosmopolitanism occurred recurrently during the geologic past, especially after mass extinctions, but the underlying mechanisms remain poorly known. Three theoretical models, not mutually exclusive, can lead to cosmopolitanism: (1) selective extinction in endemic taxa, (2) endemic taxa becoming cosmopolitan after the extinction and (3) an increase in the number of newly originated cosmopolitan taxa after extinction. We analyzed an updated occurrence dataset including 831 middle Permian to Middle Triassic ammonoid genera and used two network methods to distinguish major episodes of ammonoid cosmopolitanism during this time interval. Then, we tested the three proposed models in these case studies. Our results confirm that at least two remarkable cosmopolitanism events occurred after the Permian–Triassic and late Smithian (Early Triassic) extinctions, respectively. Partitioned analyses of survivors and newcomers revealed that the immediate cosmopolitanism event (Griesbachian) after the Permian–Triassic event can be attributed to endemic genera becoming cosmopolitan (model 2) and an increase in the number of newly originated cosmopolitan genera after the extinction (model 3). Late Smithian cosmopolitanism is caused by selective extinction in endemic taxa (model 1) and an increase in the number of newly originated cosmopolitan genera (model 3). We found that the survivors of the Permian–Triassic mass extinction did not show a wider geographic range, suggesting that this mass extinction is nonselective among the biogeographic ranges, while late Smithian survivors exhibit a wide geographic range, indicating selective survivorship among cosmopolitan genera. These successive cosmopolitanism events during severe extinctions are associated with marked environmental upheavals such as rapid climate changes and oceanic anoxic events, suggesting that environmental fluctuations play a significant role in cosmopolitanism.

Wildfire evidence from the Middle and Late Permian Hanxing Coalfield, North China Basin

Earth has a long geological history and palaeo-wildfire is one of the key factors which is responsible for the evolution and extinction of our earth systems. The most important extinction of our earth systems is the Permian-Triassic mass extinction. The objective of this paper is to evaluate the product of wildfire in terms of distribution and occurrences from the Late Permian North China basin. Fourteen rock samples were collected from a drill core of Hanxing Coalfield of North China basin. The samples were analyzed by macro and micro petrography, Scanning Electron Microscopy (SEM), Gas Chromatography (GC) and Gas Chromatography–Mass Spectrometry (GC-MS) in order to study the evidence of wildfire. Charcoal (inertinite) particles are observed in the samples, which established the occurrences of wildfire during the upper Middle and Late Permian time in North China. Additionally, high-molecular-weight Polycyclic Aromatic Hydrocarbons (PAHs) were detected in the studied samples which also reinforce the presence of palaeo–wildfire events in the North China basin in Late Permian due to the fact that these aromatic compounds were formed under high temperatures.