end-Permian Mass Extinction Event Research Articles

Quantitative constraints on carbon cycling and temporal changes in episodic euxinia during the end-Permian mass extinction in South China

We report the temporal and spatial C-isotopic variations of carbonate (δ13Ccarb) and organic carbon (δ13Corg) spanning the Permian-Triassic transition at the Xiakou and Chaotian sections in South China. The C-isotope data from the two sections show two episodes of δ13Ccarb decrease. However, in contrast to most of the C-isotopic records of the Phanerozoic, the changes in δ13Corg are not paralleled by those of δ13Ccarb: rather, they show a gradual increase followed by a consistent negative excursion. Accordingly, the C-isotopic data exhibit two episodes of decreased Δ13Ccarb-org (Δ13Ccarb-org = δ13Ccarb – δ13Corg). A dual-reservoir model was used to study the main factors responsible for the C-isotopic excursions. We show that two episodes of decrease in δ13Ccarb and Δ13Ccarb-org may be best explained by the remineralization of organic carbon and the proliferation of green sulfur bacteria, which may have been driven by the episodic incursion of sulfidic waters. The temporal and spatial variations of δ13Ccarb and δ13Corg reveal two episodic incursions of sulfidic waters into shallow water areas with resulting photic zone euxinia. The first incursion of sulfidic waters occurred before the end-Permian mass extinction (EPME) event, while the second incursion occurred across the EPME event. The modeling results show that the amount of 13C-depleted carbon input from remineralization across the EPME is ~1.5-times that before the EPME, providing quantitative evidence for the temporal changes in episodic euxinia. This conclusion is strengthened by the observed δ13C depth gradient between the two sections. Our results provide quantitative constraints on carbon cycling in the Permian-Triassic oceans and suggest that the expanded euxinia may have crossed a threshold that led to the most severe biotic crisis in Earth's history.

Oceanic water redox conditions of the region between Tethys and Panthalassa during the late early Triassic

Fossil evidence of a complex food-chain in the marine ecosystem after the end-Permian mass extinction (EPME) event has been reported from the Osawa Formation, which consists of upper Olenekian (Spathian) shallow marine, mudstone-dominant strata in the South Kitakami Belt in Northeast Japan. This sedimentary sequence offers an important material that records the paleoenvironment of the oceanic region between the eastern Tethys and Panthalassa. This paper reports detailed records of the oceanic environment from two sections of the Osawa Formation focusing on the redox condition. Parallel, undisturbed laminae suggesting limited benthic activity are prominent in the middle to upper parts of the Osawa Formation, while disturbance of laminae by burrows occurs in the lower and uppermost parts, suggesting active benthic activity in an oxygen-rich depositional environment. The amount of pyrites (euhedral pyrite, pyrite framboids, and pyrite polyframboids) increases in the well-laminated mudstones. A relatively broad size distribution of pyrite framboids indicates that these mudstones were deposited under dysoxic conditions and suggest that the water column was not sulfidic. Redox-sensitive elements such as Mn, V, and U show values close to the average values of the upper continental crust throughout the Osawa Formation. Mo is moderately enriched in the well-laminated and pyrite-abundant mudstone horizons although the degree of enrichment is lower than known examples of modern sulfidic basins. These data suggest that the condition of the bottom water in this oceanic region during the Spathian varied between oxic and dysoxic (weakly oxygenated) and was never sulfidic. Such an oceanic environment characterized by mildly reducing bottom water and oxic water column appears to have been the settings for the recovery and establishment of the Early Triassic marine ecosystem characterized by diverse nektonic motile animals and limited diversity of benthic, in-motile animals.

Revision of Cyclida (Pancrustacea, Multicrustacea), with five new genera

All cyclidan species represented by existing material are illustrated photographically. New genera within Cyclidae include Ambocyclus new genus; Carabicyclus new genus; Chernyshevine new genus, Litocyclus new genus; and Tazawacyclus new genus with the following new combinations: A. capidulum (Chernyschev, 1933); A. simulans (Reed, 1908); A. ? minutus (Rogers, 1902); Carabicyclus wrighti (Woodward, 1870); L. bilobatus (Woodward, 1870); L. ? communis (Rogers, 1902); L. jonesianus (Woodward, 1870); L. ? permarginatus (Rogers, 1902); L. torosus (Woodward, 1870); Chernyshevine spinosus (Chernyschev, 1933); T. tazawai (Niko & Ibaraki, 2011); U. harknessi (Woodward, 1870); and U. woodwardi (Reed, 1893). New genera within Americlidae include Brittaniclus and Dziklus with the following new combinations: B. rankini (Woodward, 1868); B. scotti (Woodward, 1894); B. testudo (Peach, 1882); and D. obesus (Schram, Vonk & Hof, 1997). A neotype is herein designated for Halicyne plana. Each family within Cyclida occupies a distinct morphospace. Two families survived the end-Permian mass extinction event. Most cyclidans occupied marine conditions, but some are known from marginal marine and freshwater environments.

Proxy evidence from the Gartnerkofel-1 core (Carnic Alps, Austria) for hypoxic conditions in the western Tethys during the end-Permian mass-extinction event

The most severe mass extinction in the Phanerozoic in the latest Permian Period (251.9 Ma), has been attributed to environmental effects related to the massive coeval Siberian flood-basalt eruptions. A potential causal link between the eruptions and the marine extinctions arises from lethal global warming from greenhouse-gas emissions and the resulting development of widespread hypoxic conditions in the warm oceans. The 331-m Gartnerkofel-1 core (Carnic Alps, Austria) penetrated the Permian-Triassic boundary interval in a western Tethys shallow carbonate-ramp setting. We calculated U/Th ratios and element-enrichment factors (for U, Cr, V, Co, and Ni) using the previously published raw elemental data from the core. These redox-sensitive proxy calculations provide evidence for an ~60-ky long episode of anoxic to euxinic ocean conditions in the shallow western Tethys at the time of the abrupt end-Permian mass extinction (EPME). Subsequent fluctuating dysoxic conditions were coincident with a negative excursion of δ13Ccarb that is estimated to have lasted ~450 ky in the earliest Triassic at the GK-1 site. These findings in a high-deposition-rate section support previous reports of widespread anoxia in the western Tethys, and in the oceans in general, coincident with the EPME and its aftermath.

Evolutionary and ecophenotypic controls on bivalve body size distributions following the end-Permian mass extinction

Abstract Mass extinction events are characterized by major losses in faunal diversity and are associated with several other ecological effects, e.g., reductions in tiering, selective losses of ecological lifestyles, and body size reductions. The latter has received considerable attention and debate, as to whether the reduced size of post-extinction organisms is due to the selective extinction of large species, absence of large species as a stochastic effect of low-diversity faunas (the Gulliver absence effect), a size decrease within surviving genera and species (the Lilliput effect), or a combination of these factors. Here, we investigated both evolutionary and ecophenotypic controls on body size distributions following the end-Permian mass extinction event by investigating size changes in bivalves (Claraia, “Unionites”, and Neoschizodus) from the Werfen Formation (Dolomites, Italy) and the Bodvaszilas Sandstone Formation (Aggtelek Karst, Hungary). Our results show that the Early Triassic shell size increase of bivalve genera was driven by both evolutionary and ecophenotypic responses. First, genera Claraia and “Unionites” show significant increases in body size with the appearance of the new species C. clarai and “U”. canalensis, respectively, suggesting that evolution played a role on Early Triassic bivalve body size dynamics. Further, the same genera record significant within-species increases in average and maximum body size into the late Griesbachian and Dienerian stages (the Brobdingnag effect), indicating that within-species ecophenotypic changes were also involved on observed long-term body size trends. These increases are associated with invigorated ocean circulation, improved oxygenation of the seafloor, and probably increased food supply. We, therefore, hypothesize that both growth-limiting environmental conditions (deoxygenation and reduced primary productivity) and the extinction-induced absence of large species led to small-sized species dominating early Griesbachian benthic invertebrate communities.

Suppressed competitive exclusion enabled the proliferation of Permian/Triassic boundary microbialites.

During the earliest Triassic microbial mats flourished in the photic zones of marginal seas, generating widespread microbialites. It has been suggested that anoxic conditions in shallow marine environments, linked to the end‐Permian mass extinction, limited mat‐inhibiting metazoans allowing for this microbialite expansion. The presence of a diverse suite of proxies indicating oxygenated shallow sea‐water conditions (metazoan fossils, biomarkers and redox proxies) from microbialite successions have, however, challenged the inference of anoxic conditions. Here, the distribution and faunal composition of Griesbachian microbialites from China, Iran, Turkey, Armenia, Slovenia and Hungary are investigated to determine the factors that allowed microbialite‐forming microbial mats to flourish following the end‐Permian crisis. The results presented here show that Neotethyan microbial buildups record a unique faunal association due to the presence of keratose sponges, while the Palaeotethyan buildups have a higher proportion of molluscs and the foraminifera Earlandia. The distribution of the faunal components within the microbial fabrics suggests that, except for the keratose sponges and some microconchids, most of the metazoans were transported into the microbial framework via wave currents. The presence of both microbialites and metazoan associations were limited to oxygenated settings, suggesting that a factor other than anoxia resulted in a relaxation of ecological constraints following the mass extinction event. It is inferred that the end‐Permian mass extinction event decreased the diversity and abundance of metazoans to the point of significantly reducing competition, allowing photosynthesis‐based microbial mats to flourish in shallow water settings and resulting in the formation of widespread microbialites.

Are stromatolites in the northern Perth Basin following the End Permian mass extinction?

Following the End Permian Mass Extinction (EPME) event, global stromatolite distributions rapidly increased. There are three documented examples of stromatolites occurring in intracontinental setti...

End-Permian (252 Mya) deforestation, wildfires and flooding—An ancient biotic crisis with lessons for the present

Current large-scale deforestation poses a threat to ecosystems globally, and imposes substantial and prolonged changes on the hydrological and carbon cycles. The tropical forests of the Amazon and Indonesia are currently undergoing deforestation with catastrophic ecological consequences but widespread deforestation events have occurred several times in Earth's history and these provide lessons for the future. The end-Permian mass-extinction event (EPE; ∼252 Ma) provides a global, deep-time analogue for modern deforestation and diversity loss. We undertook centimeter-resolution palynological, sedimentological, carbon stable-isotope and paleobotanical investigations of strata spanning the end-Permian event at the Frazer Beach and Snapper Point localities, in the Sydney Basin, Australia. We show that the typical Permian temperate, coal-forming, forest communities disappeared abruptly, followed by the accumulation of a 1-m-thick mudstone poor in organic matter that, in effect, represents a ‘dead zone’ hosting degraded wood fragments, charcoal and fungal spores. This signals a catastrophic scenario of vegetation die-off and extinction in southern high-latitude terrestrial settings. Lake systems, expressed by laterally extensive but generally less than a few-metres-thick laminated siltstones, generally lacking bioturbation, hosting assemblages of algal cysts and freshwater acritarchs, developed soon after the vegetation die-off. The first traces of vascular plant recovery occur ∼1.6 m above the extinction horizon. Based on analogies with modern deforestation, we propose that the global fungal and acritarch events of the Permo-Triassic transition resulted directly from inundation of basinal areas following water-table rise as a response to the abrupt disappearance of complex vegetation from the landscape. The δ13Corg values reveal a significant excursion toward low isotopic values, down to −31‰ (a shift of ∼4‰), across the end-Permian event. The magnitude of the shift at that time records a combination of changes in the global carbon cycle that were enhanced by the local increase in microbial activity, possibly also involving cyanobacterial proliferation. We envisage that elevated levels of organic and mineral nutrients delivered from inundated dead forests, enhanced weathering and erosion of extra-basinal areas, together with local contributions of volcanic ash, led to eutrophication and increased salinity of basinal lacustrine–lagoonal environments. We propose that the change in acritarch communities recorded globally in nearshore marine settings across the end-Permian event is to a great extent a consequence of the influx of freshwater algae and nutrients from the continents. Although this event coincides with the Siberian trap volcanic activity, we note that felsic–intermediate volcanism was extensively developed along the convergent Panthalassan margin of Pangea at that time and might also have contributed to environmental perturbations at the close of the Permian.

High-resolution variation in ostracod assemblages from microbialites near the Permian-Triassic boundary at Zuodeng, Guangxi region, South China

After the end-Permian mass extinction (EPME), the marine environment was considered extremely toxic, mainly due to anoxic and high-temperature conditions and ocean acidification; consequently, the ecosystem contained few organisms. This paper describes a new ostracod fauna from the microbialite-bearing Permian-Triassic (P-Tr) strata at Zuodeng, Guangxi region, China. One thousand and seventy ostracod specimens were extracted from forty-eight samples. Fifty-three species belonging to fourteen genera were identified. Ostracods, primarily from the family Bairdiidae, were extremely abundant in the microbialites, which suggests that ostracods were opportunists that could survive the EPME within this special microbial ecosystem with sufficient food and scarce competitors and predators rather than undergoing a rapid and early recovery after the EPME event. Ostracods having simultaneous Paleozoic and Meso-Cenozoic affinities coexisted in this fauna. The similarities and differences among the ostracod faunas in the microbialite sections of the P-Tr boundary around the Paleo-Tethys indicate that there was a long-distance dispersal of ostracods, but the faunas maintained endemism at the species level. Previous studies have regarded microbialites as whole units, and it is difficult to detect environmental changes within a microbialite interval based on paleoecological groups of (super)families. In this study, high-resolution sampling was applied to identify changes in the ostracod abundance, diversity, assemblages and proportion of five dominant species in the section, which exhibited an evolutionary trend from the “Bairdia” group to the “Liuzhinia antalyaensis-Bairdiacypris ottomanensis” group. Furthermore, the transition of the ostracod fauna could be divided into six stages according to changes in the dominant species groups, suggesting that the microbialite environment was not entirely monotonous but fluctuated during the postextinction interval.

Frequent and intense fires in the final coals of the Paleozoic indicate elevated atmospheric oxygen levels at the onset of the End-Permian Mass Extinction Event

During the End-Permian mass extinction event (EPME) there is extensive evidence for depletion of oxygen in the marine realm. Atmospheric models based upon biogeochemical cycling predict a comparable decline leading up to this event and have been postulated as a possible driver for marine depletion. However, these models contrast with broadly contemporaneous empirical evidence from charcoal in coals. New charcoal data from the temporally well-constrained late Permian Xuanwei Formation coals of eastern Yunnan Province, China, deposited just prior to the onset of the Permian-Triassic Transitional Beds, supports the coarser analysis and further challenges these biogeochemical models. Inertinite group macerals, comprising fusinite, semifusinite, macrinite, inertodetrinite, secretinite, all funginite with elevated reflectance, and some micrinite, are proxies for wildfire activity, and indicate abundant evidence for this phenomenon in the latest Permian and preclude low levels of atmospheric oxygen concentration coevally. Henceforward, we will employ the term ‘inertinite group macerals sensu amplo’ to refer to just these precise macerals, though these encompass what are the overwhelming preponderance of inertinites in most coals. Both inertinite abundance and reflectance indicate an increase in fire activity and intensity towards the End-Permian faunal crisis. Quantitatively, these inertinite data indicate atmospheric oxygen concentration was high and at the close of the Paleozoic was probably elevated to levels well above those of the present-day. The elevated fire activity at this time may have functioned as a causal link to explain some localized oxygen depletion in the marine realm as a result of post-fire increased run-off and erosion. However, globally depressed atmospheric oxygen concentration at the End-Permian was not a driver of extensive marine anoxia at that time.

Natural assemblages of the conodont Clarkina in lowermost Triassic deep-sea black claystone from northeastern Japan, with probable soft-tissue impressions

We report the first discovery of Lower Triassic Clarkina assemblages: four natural conodont assemblages from Lower Triassic pelagic black claystones of the North Kitakami Belt in northeastern Japan (Akkamori section). The fossils were obtained from the 2.5-m horizon level above the black claystone base, which is assigned to the end-Permian mass-extinction event. This horizon has been dated to the earliest Triassic (Griesbachian) by the occurrence of Hindeodus parvus, which is the index species for the base of the Triassic, in the same and subjacent horizons. These four fossil assemblages include a paired segminiplanate-formed P1 element, which was identified as the genus Clarkina, and have fully or partially preserved the original components of conodont elements. The most complete assemblage among them includes 15 distinctive elements, namely S0 and pairs of M, S1, S2, S3, S4, P1, and P2. It is noteworthy that these fossil assemblages preserve probable impressions of ‘eyes,’ which were replaced by aggregations of silicate, phosphate, and sulphide minerals. The occurrence of several sets of fossils that retain the original positioning of the conodonts' elemental apparatuses, as well as the original presence of soft tissue, may be attributed to the process by which the conodonts' bodies were transported to the deep seafloor, and by which the activity of agents of decomposition was inhibited in near-abiotic sediments under anoxic conditions in the pelagic deep sea during the earliest Triassic.

Species richness and disparity of parareptiles across the end-Permian mass extinction.

The amniote clade Parareptilia is notable in that members of the clade exhibited a wide array of morphologies, were successful in a variety of ecological niches and survived the end-Permian mass extinction. In order to better understand how mass extinction events can affect clades that survive them, we investigate both the species richness and morphological diversity (disparity) of parareptiles over the course of their history. Furthermore, we examine our observations in the context of other metazoan clades, in order to identify post-extinction survivorship patterns that are present in the clade. The results of our study indicate that there was an early increase in parareptilian disparity, which then fluctuated over the course of the Permian, before it eventually declined sharply towards the end of the Permian and into the Triassic, corresponding with the end-Permian mass extinction event. Interestingly, this is a different trend to what is observed regarding parareptile richness, that shows an almost continuous increase until its overall peak at the end of the Late Permian. Moreover, richness did not experience the same sharp drop at the end of the Permian, reaching a plateau until the Anisian, before dropping sharply and remaining low, with the clade going extinct at the end of the Triassic. This observed pattern is likely to be due to the fact that, despite the extinction of several morphologically distinct parareptile clades, the procolophonoids, one of the largest parareptilian clades, were diversifying across the Permian-Triassic boundary. With the clade's low levels of disparity and eventually declining species richness, this pattern most resembles a 'dead clade walking' pattern.

A novel archosauromorph from Antarctica and an updated review of a high-latitude vertebrate assemblage in the wake of the end-Permian mass extinction

Triassic-aged fossil vertebrates have been sporadically collected from the Fremouw Formation, central Transantarctic Mountains, since their initial discovery in the late 1960s, giving paleontologists insight into high-latitude faunas in the wake of the end-Permian mass extinction event. On a recent expedition (2010–2011), a small reptile skeleton was collected from Graphite Peak, which we present here alongside novel geological data and interpretations taken on site. Antarctanax shackletoni, gen. et sp. nov., is known from a partial postcranial skeleton including cervical and dorsal vertebrae, a humerus, and both pedes. Important morphological information includes well-defined laminae and deep fossae on cervicodorsal vertebrae. The new taxon can be differentiated from previously known Fremouw Formation reptiles (e.g., Prolacerta, Procolophon), as well as those from the Karoo Basin, South Africa (e.g., Mesosuchus, Proterosuchus, Euparkeria). Our inclusion of A. shackletoni in phylogenetic analyses of early amniotes finds it as an archosauriform archosauromorph, increasing known archosauriform diversity in the Early Triassic. The fauna of the lower Fremouw Formation traditionally has been considered to represent a subset of the Lystrosaurus Assemblage Zone of the Karoo Basin, with differences largely a result of pronounced differences in sampling intensity. However, a review of recent changes to the fauna, as well as a reassessment of occurrences based on older literature, indicates that significant discrepancies, including the co-occurrences of taxa known from both earlier and later in time and the presence of endemic forms in Antarctica, exist between the faunas of the Lystrosaurus Assemblage Zone and lower Fremouw Formation.http://zoobank.org/urn:lsid:zoobank.org:pub:B1DAD1A4-7054-454D-89B2-17CAF2865AD4SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Peecook, B. R., R. M. H. Smith, and Christian A. Sidor. 2019. A novel archosauromorph from Antarctica and an updated review of a high-latitude vertebrate assemblage in the wake of the end-Permian mass extinction. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1536664.

An Early Triassic (Dienerian) microgastropod assemblage from the Salt Range, Pakistan and its implication for gastropod recovery from the end-Permian mass extinction

A single limestone sample from the Early Triassic (late Dienerian) of the Salt Range in Pakistan has yielded numerous small gastropods (smaller 2 mm), few bivalves and abundant ammonoids. The limestone is interpreted as a tempestite. Many of the gastropods are extremely well-preserved including protoconch preservation and micro-ornaments. Five species of gastropods are present: (1) isolated larval shells representing a neritimorph taxon of the family Trachyspiridae, (2) early juvenile and larval specimens of the caenogastropod Strobeus pakistanensis, (3) the new caenogastropod species Coelostylina hydrobifomis Nutzel & Ware, (4) the new heterobranch genus and species Eographis microlineata Ntitzel & Ware representing the earliest occurrence of the extant family Hyalogyrinidae (Valvatoidea), (5) the heterobranch Sinuarbullina sp., a genus which originates in the Early Triassic and has also been reported from China, Spitsbergen and the US. Three genera (trachyspirid. Strobeus and Coelostylina) represent survivors from the end-Permian mass extinction whereas Eographis and Sinuarbullina have their earliest known occurrence in the Early Triassic. Eographis is the first Early Triassic genus for which coaxial larval heterostrophy is shown. Together with the Devonian genus Palaeocarboninia and the Carboniferous genus Heteroaclisina, it witnesses a high age of Ectobranchia (living families Hyalogyrinidae, Valvatidae. Comirostridae and Xylodisculidae). This supports the assumption that this group is the first extant offshoot of the Heterobranchia. The studied assemblage is strongly dominated by Strobeus pakistanesis. The small size of the gastropods reflects their ontogenetic stage (early juvenile and larval shells) as well as a small adult size in some of the species. Most of the present gastropods had planktotrophic larval development providing further evidence against the hypothesis that the end-Permian mass extinction event selected against larval planktotrophy. Failure to grow to a larger size or to perform metamorphosis suggests unfavourable living conditions in the source community probably due to oxygen deficiency prior to transport by storm. Size sorting is seen as less likely because the limestone is poorly sorted with relatively large ammonoids being present in considerable numbers. The studied sample yielded also three bivalve taxa amongst them two species representing the genera Leptochondria and Crittendenia.

Caudal autotomy as anti-predatory behaviour in Palaeozoic reptiles

Many lizards can drop a portion of their tail in response to an attack by a predator, a behaviour known as caudal autotomy. The capacity for intravertebral autotomy among modern reptiles suggests that it evolved in the lepidosaur branch of reptilian evolution, because no such vertebral features are known in turtles or crocodilians. Here we present the first detailed evidence of the oldest known case of caudal autotomy, found only among members of the Early Permian captorhinids, a group of ancient reptiles that diversified extensively and gained a near global distribution before the end-Permian mass extinction event of the Palaeozoic. Histological and SEM evidence show that these early reptiles were the first amniotes that could autotomize their tails, likely as an anti-predatory behaviour. As in modern iguanid lizards, smaller captorhinids were able to drop their tails as juveniles, presumably as a mechanism to evade a predator, whereas larger individuals may have gradually lost this ability. Caudal autotomy in captorhinid reptiles highlights the antiquity of this anti-predator behaviour in a small member of a terrestrial community composed predominantly of larger amphibian and synapsid predators.

Palaeoenvironmental change across the Permian-Triassic boundary inferred from palynomorph assemblages (Godavari Graben, south India)

In the present study, palynological and palaeoenvironmental investigations have been carried out on a 601 m-thick sedimentary sequence intersected by borehole MCP-8 (Sattupalli-Chintalapudi coal belt, Chinatalapudi sub-basin, Godavari Graben). These studies have been carried out for the dating and correlation of sediments to understand the biostratigraphy and climatic change documented by terrestrial plant ecosystem across the Permian-Triassic boundary interval. The palynological investigation revealed the presence of five distinct floral assemblages (Assemblages I–V). Assemblages I–III (Guadalupian-Lopingian) represent Raniganj palynoflora (591.27–157.20 m), whereas Assemblages IV–V (Induan) represent Panchet palynoflora (137.79–136.08 m). The Gondwanan flora underwent a considerable change after the end-Permian mass extinction event. The late Permian glossopterids, conifer and cordaites dominated palynoflora was replaced by the lycopsids and few forms of peltasperms and conifers during Early Triassic. The decline in the glossopterid diversity and abundance along with concomitant rise in the lycopsids suggest a gradual but obvious palynofloral and environmental change across the Permian-Triassic boundary. Palynofacies studies have been carried with regards to reconstruct palaeoenvironment and palaeovegetation. These studies predict a thick closed forest cover during the deposition of the Raniganj palynoflora (late Permian), dominated by striate glossopterid and non-striate conifer and peltasperm pollen grains, which were the main peat-forming elements and the vegetation of the hinterland. The Panchet (Early Triassic) palynoflora was dominated by cingulate cavate spore bearing lycopsids and arborescent to sub-arborescent plants of conifers bearing taeniate bisaccates forming an open forest. On the basis of recovered palynoflora and palynofacies studies, the upper Permian (Guadalupian and lower Lopingian) deposits have been inferred as fluvio lacustrine while extensive peat-forming swamp dominating conditions prevailed during Changhsingian times. The Lower Triassic deposits represent hot-arid conditions along the braided river systems.

Lycopodiopsids and equisetopsids from the Triassic of Quebrada de los Fósiles Formation, San Rafael Basin, Argentina

In the late 1960s, rests of a low-diversity flora dominated by the lycopsid Pleuromeia were reported. The specimens were recovered from a creek near San Rafael, Mendoza Province, western Argentina, in the lower section of the Puesto Viejo Group, the Quebrada de los Fósiles Formation, considered as Early Triassic in age. Despite the importance of this flora with respect to the end-Permian mass extinction event, it was not yet described nor illustrated. Since then, the age of the Puesto Viejo Group has been revised and the Quebrada de los Fósiles Formation is now considered to be early Middle Triassic. The fossil plants are here first described and interpreted. The most common element, Pleuromeia cf. sternbergii, a species known worldwide that characterizes the post-extinction flora recovery, is accompanied by sphenopsids such as Neocalamites and Equisetostachys, and an herbaceous lycopsid. This community grew up associated with transient water bodies in flood plain environments that developed under warm temperate, strongly seasonal climatic conditions. The landscape was stressed by volcanism, and the conjunction of these factors probably restricted the colonization and development of a full ecosystem, as happened worldwide after the end-Permian mass extinction.

Redescription of Saurichthys madagascariensis Piveteau, 1945 (Actinopterygii, Early Triassic), with implications for the early saurichthyid morphotype

ABSTRACTRay-finned fishes of the Saurichthyidae radiated rapidly after the end-Permian mass extinction event and became important predators within Triassic marine and freshwater ecosystems. Despite their extensive fossil record, the early evolution of saurichthyids still remains obscure. In an attempt to address this problem, we restudied Saurichthys madagascariensis, a key species from the Early Triassic of Madagascar (maximum age range middle Dienerian–early Smithian according to the available biostratigraphic data discussed herein), on the basis of ∼160 specimens, including several new, nearly complete individuals. Saurichthys madagascariensis is a medium-sized (ca. 60 cm) saurichthyid with a well-ossified circumorbital series, a suborbital, an antoperculum, one pair of branchiostegal rays, all fins with segmented, branched lepidotrichia and fringing fulcra, and an extensive squamation consisting of specialized scales arranged in six longitudinal rows, with rhombic scales in between. A series of ‘L’-shaped ventrolateral scales may be apomorphic for the Madagascan species. Comparisons among early saurichthyids reveal some shared traits, based upon which we hypothesize that the primitive condition of Saurichthyidae includes (1) broad scutes along the dorsal and ventral midlines articulating with one another via a specialized ‘keel and groove articulation’; (2) high, anteriorly inclined flank scales subdivided by the lateral line sensory canal into a tuberculated dorsal and a vertically striated ventral portion; (3) posteriorly inclined ventrolateral scales; and (4) a 1:2 relationship between the mid-lateral scales and the neural arches. These data may help to resolve problems in phylogenetic studies concerning synapomorphies and convergences of saurichthyids with other taxa.Citation for this article: Kogan, I., and C. Romano. 2016. Redescription of Saurichthys madagascariensis Piveteau, 1945 (Actinopterygii, Early Triassic), with implications for the early saurichthyid morphotype. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1151886.

Depositional conditions and revised age of the Permo-Triassic microbialites at Gaohua section, Cili County (Hunan Province, South China)

In many tropical shallow water regions the end-Permian mass extinction event occurs at the top fossiliferous packstone beds and is immediately followed by the development of microbialite facies. Both the age and redox conditions of the microbialite have been debated and both factors are addressed here in a study of the Gaohua section (Cili County, Hunan Province, China): specifically the size distribution of pyrite framboids and high-resolution conodont biostratigraphy. The framboids populations show a broad size range with examples up to 30microns in diameter, and indicating dysoxic but not anoxic depositional conditions. More intense dysoxia is recorded in interbedded laminated micrites but not beds of giant ooids. Both the Hindeodus parvus zone and Isarcicella isarcica zones were established with the microbialite beds being confined to the H. parvus zone. Therefore, the formation of microbialite postdates the end Permian main mass extinction and records oxygen-poor conditions even in a shallow-water setting such as Gaohua section at Cili.

Carbon cycle perturbation expressed in terrestrial Permian–Triassic boundary sections in South China

Stable isotopes of inorganic and organic carbon are commonly used in chemostratigraphy to correlate marine and terrestrial sedimentary sequences based on the assumption that the carbon isotopic signature of the exogenic carbon pool dominates other sources of variability. Here, sediment samples from four Permian–Triassic boundary (PTB) sections of western Guizhou and eastern Yunnan provinces in South China, representing a terrestrial to marine transitional setting, were analyzed for δ13C of organic matter (δ13Corg). These values were subsequently compared to published δ13C values of carbonates (δ13Ccarb) from the Global Stratotype Section and Point at Meishan and many other marine and terrestrial sections. A similar isotopic trend evident through all four sections is characterized by a negative shift of 2–3‰ at the top of the Xuanwei Formation, where we tentatively place the PTB. This negative shift also corresponds to a turnover in the vegetation and the occurrence of fungal spores, which is generally interpreted as a proliferation of decomposers and collapse of complex ecosystems during the end-Permian mass extinction event. Moreover, the absolute values of δ13Corg are more extreme in the more distal (marine) deposits. The δ13Corg values for the studied sediments are more variable compared to coeval δ13Ccarb records from marine records especially in the interval below the extinction horizon. We contend that the depositional environment influenced the δ13Corg values, but that the persisting geographic δ13Corg pattern through the extinction event across the four independent sections is an indication that the atmospheric δ13C signal left an indelible imprint on the geologic record related to the profound ecosystem change during the end-Permian extinction event.