Recovery From the Permian Extinction Delayed by Productivity Crises During Early Triassic

Early Triassic productivity crises delayed recovery from world's worst mass extinction

Authors:

Grasby et al

Abstract:

The recovery of life after the latest Permian extinction was protracted over Early Triassic time. Detailed geochemistry of marine sections along northwest Pangea indicates that upwelling ceased at the extinction event. Nitrogen stable isotope data suggest that this was associated with progressive increase in nutrient stress throughout the Early Triassic, coincident with a significant decrease in organic carbon content despite pervasive anoxic to euxinic conditions. We argue that the Early Triassic hothouse both reduced marine productivity and deepened the nutricline, reducing the overall rate of nutrient delivery to the photic zone, creating an Early Triassic nutrient gap. When oceans finally cooled by Middle Triassic time, renewed nutrient upwelling and onset of organic-rich shale deposition occurred across northwest Pangea, marking the final return of global marine productivity.

Iron-rich, Hyopxic Seas Might Have Helped Delay Biotic Recovery After the Permian Extinction

Scientists have shed light on why life on Earth took millions of years to recover from the greatest mass extinction of all time.

The study provides fresh insight into how Earth's oceans became starved of oxygen in the wake of the event 252 million years ago, delaying the recovery of life by five million years.

Findings from the study are helping scientists to better understand how environmental change can have disastrous consequences for life on Earth.

The Permian-Triassic Boundary extinction wiped out more than 90 per cent of marine life and around two thirds of animals living on land. During the recovery period, Earth's oceans became starved of oxygen - conditions known as anoxia.

Previous research suggested the mass extinction and delayed recovery were linked to the presence of anoxic waters that also contained high levels of harmful compounds known as sulphides.

However, researchers say anoxic conditions at the time were more complex, and that this toxic, sulphide-rich state was not present throughout all the world's oceans.

The team, led by researchers at the University of Edinburgh, used precise chemical techniques to analyse rocks unearthed in Oman that were formed in an ancient ocean around the time of the extinction.

Data from six sampling sites, spanning shallow regions to the deeper ocean, reveal that while the water was lacking in oxygen, toxic sulphide was not present. Instead, the waters were rich in iron.

The finding suggests that iron-rich, low oxygen waters were a major cause of the delayed recovery of marine life following the mass extinction.

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How Dominant Were Disaster Taxa After the Permian Extinction

Quantitative analysis of the ecological dominance of benthic disaster taxa in the aftermath of the end-Permian mass extinction

Authors:

Petsios et al

Abstract:

The end-Permian mass extinction, the largest extinction of the Phanerozoic, led to a severe reduction in both taxonomic richness and ecological complexity of marine communities, eventually culminating in a dramatic ecological restructuring of communities. During the Early Triassic recovery interval, disaster taxa proliferated and numerically dominated many marine benthic invertebrate assemblages. These disaster taxa include the bivalve genera Claraia, Unionites, Eumorphotis, and Promyalina, and the inarticulate brachiopod Lingularia. The exact nature and extent of their dominance remains uncertain. Here, a quantitative analysis of the dominance of these taxa within the fossil communities of Panthalassa and Tethys benthic realms is undertaken for the stages of the Early Triassic to examine temporal and regional changes in disaster-taxon dominance as recovery progresses. Community dominance and disaster-taxon abundance is markedly different between Panthalassic and Tethyan communities. In Panthalassa, community evenness is low in the Induan stage but increases significantly in the Smithian and Spathian. This is coincident with a significant decrease in the relative abundance and occurrence frequency of the disaster taxa, most notably of the low-oxygen-affinity taxa Claraia and Lingularia. While the disaster taxa are present in post-Induan assemblages, other taxa, including two articulate brachiopod genera, outrank the disaster taxa in relative abundance. In the Tethys, assemblages are generally more even than contemporaneous Panthalassic assemblages. We observe an averaged trend toward more even communities with fewer disaster taxa in both Panthalassic and Tethyan assemblages over time.

The Oceans Recovered From the Permian Mass Extinction Quickly

Reptiles rapidly invaded the seas soon after a global extinction wiped out most life on Earth, according to a new study led by University of California, Davis, researchers.

Global climate change -- likely triggered by massive volcanic eruptions -- killed off more than 95 percent of all species about 250 million years ago, at the end of the Permian period. Land reptiles colonized the ocean in just 3.35 million years at the beginning of the Triassic, a speedy recovery in geologic time, the researchers report today (June 13) in the journal Scientific Reports.

"Our results fit with the emerging view that the recovery was faster than previously thought," said study co-author Ryosuke Motani, professor of paleobiology at UC Davis' Department of Earth and Planetary Sciences.

The research was led by Wanlu Fu, now of the Laboratory of Orogenic Belt and Crustal Evolution at Peking University. Fu conducted the research while an in-residence doctoral student working with study co-author Isabel Montañez, professor of geochemistry at UC Davis. Co-authors include scientists from the University of Wisconsin and the University of Milan in Italy. The fossils and rock samples were collected from Majiashan in Chaohu, South China.

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Post Permian Triassic Extinction Biota NOT a Disaster Ecology?

Sudden and extreme hyperthermals, low-oxygen, and sediment influx drove community phase shifts following the end-Permian mass extinction

Authors:

Pietsch et al

Abstract:

We present a correlated record of carbon isotope geochemistry and sedimentological analysis for the Lower Triassic Werfen Formation from the Italian Dolomites. Macro- and mid-sized fossil diversity, ecology, and climate sensitivity are included to provide an integrated account of the benthic response to paleoenvironmental change. Novel communities developed in the wake of the mass extinction during pervasive fluctuations in environmental conditions. In the sedimentary sequences of the Werfen Formation of the Italian Dolomites, microbialites, microconchids, foraminifera, and ubiquitous flat-clams, formed a complex community within the first 500,000 years. Later, increased sea-surface temperatures and inundation of the seafloor with siliciclastic sediments favored infaunal bivalves and microgastropods. Persistent trends in the environment can produce directional, often irreversible, community shifts defined here as phase shifts. Phase shifts in ecosystem structure can be driven by environmental shifts across threshold boundaries to produce an “abrupt and dramatic” novel community composition, a phenomenon readily observed during the Early Triassic. Previously described “disaster forms” including flat clams, microconchids, foraminifera, and microbialites are re-envisioned as a phase shift community. We hypothesize that the unique, persistent, and reoccurring microbialite and mid-sized fauna assemblages observed during the initial recovery from the end-Permian mass extinction and re-appearing throughout the Early Triassic typify a phase shift community. In the Smithian, infaunal bivalves and microgastropods represent a second phase shift community developed in response to a persistent, directional rise in sea-surface temperatures and enhanced sediment influx. We compare and contrast phase shifts with other models for ecosystem recovery including trophic, competition, and Earth System Succession.

The Liliput Effect Noted for the Devonian Mass Extinctions

When times are good, it pays to be the big fish in the sea; in the aftermath of disaster, however, smaller is better.

According to new research led by the University of Pennsylvania's Lauren Sallan, a mass extinction 359 million years ago known as the Hangenberg event triggered a drastic and lasting transformation of Earth's vertebrate community. Beforehand, large creatures were the norm, but, for at least 40 million years following the die-off, the oceans were dominated by markedly smaller fish.

"Rather than having this thriving ecosystem of large things, you may have one gigantic relict, but otherwise everything is the size of a sardine," said Sallan, an assistant professor in Penn's Department of Earth and Environmental Science in the School of Arts & Sciences.

The finding, which suggests that small, fast-reproducing fish possessed an evolutionary advantage over larger animals in the disturbed, post-extinction environment, may have implications for trends we see in modern species today, such as in fish populations, many of which are crashing due to overfishing. The research is reported in Science.

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Lungfish Remained Morphologically Diverse Through Romer's Gap

Lungfish diversity in Romer's Gap: reaction to the end-Devonian extinction

Authors:

Smithson et al

Abstract:

Romer's Gap, the interval following the end-Devonian extinction event, has been described as a post-extinction trough for vertebrates. It is a time roughly equivalent to the Tournaisian stage of the early Carboniferous and has been characterized by a lull in diversity of survivors. Lungfish typified this description. One species was known from one locality. Recently, a diverse collection of lungfish tooth plates, representing seven new forms, was recovered from new Tournaisian vertebrate localities in northern Britain. They display a range of previously unknown morphologies, with tooth shape and wear patterns not seen in other post-Devonian forms. A comparison of tooth ridge number and tooth ridge angle in lungfishes from the Famennian, Tournaisian and Visean reveals marked differences between late Devonian and early Carboniferous taxa. The most common tooth plate shape in the Famennian is absent from our sample of Tournaisian taxa. Two completely new shapes have evolved, one with a relatively low tooth ridge angle, no greater than 40°, in which most of the tooth ridges are essentially parallel, and the other with a much higher tooth ridge angle of up to 180° where the tooth ridges are highly divergent. This high level of morphological diversity over a narrow time period suggests that, following the end-Devonian extinction, gaps in ecospace left by the extinction of major groups of fishes were exploited by a previously unrecorded radiation of lungfishes. Whilst taxonomic diversity of lungfishes declined following the end-Devonian extinction, recovery and diversification among tooth-plated forms was rapid, and morphological disparity among these forms subsequently increased. Contrary to previous assumptions, morphological disparity among lungfish did not decline until much later in the Carboniferous.

Recovery of the Benthic Community in the Tethys After the Permian Triassic Extinction

Environmental controls on the post-Permian recovery of benthic, tropical marine ecosystems in western Palaeotethys (Aggtelek Karst, Hungary)

Authors:

Foster et al

Abstract:

Climate warming during the late Permian is associated with the most severe mass extinction event of the Phanerozoic, and the expansion of hypoxic and anoxic conditions in shallow shelf settings. It has been hypothesised that wave aeration provided a ‘habitable zone’ in the shallowest environments that allowed the survival and rapid recovery of benthic invertebrates during the Early Triassic. We test this hypothesis by studying the rock and fossil records of the Aggtelek Karst, Hungary. Nearshore settings recorded in the Bódvaszilas Sandstone Formation and units A and D of the Szin Marl Formation are characterised by taxonomically homogenous fossil assemblages of low diversity and low evenness. Ecological and taxonomic recovery in this environmental setting was hampered by persistent environmental stress. This stress is attributed to increased runoff related to climate warming during the Early Triassic that resulted in large salinity fluctuations, increased sedimentation rates and eutrophication that led to seasonal hypoxia and an environment only favourable for opportunistic taxa. In contrast, shoal and mid-ramp settings further offshore are characterised by high diversity faunas with a greater functional complexity. Prior to the late Spathian Tirolites carniolicus Zone, the shelly fossils and trace fossils are limited to settings aerated by wave activity, which supports the habitable zone hypothesis. In the Tirolites carniolicus Zone, however, the oxygen minimum zone retreats offshore and the habitable deeper shelf settings are rapidly colonised by shallow water taxa, evidenced by the highest levels of diversity and bioturbation recorded in the study. Locally, full recovery of marine ecosystems is not recorded until the Illyrian, with the establishment of a sponge reef complex.

What Crocodylomorphs Survived the KT/K-Pg Asteroid Impact Extinction in Europe

Review of the Late Cretaceous-early Paleogene crocodylomorphs of Europe: Extinction patterns across the K-PG boundary

Authors:

Puértolas-Pascual et al

Abstract:

Although the European dinosaur succession during the latest Cretaceous and its relationship with the Cretaceous-Paleogene (K-Pg) mass extinction has been the focus of recent work, other continental vertebrates, such as crocodylomorphs, have received less attention. The European continental record of crocodylomorphs in general, and of eusuchians in particular, is relatively dense through the Maastrichtian until the K-Pg boundary. Traditionally it has been argued that continental crocodylomorphs were minimally impacted by the K-Pg extinction, but they were substantially affected in Europe with the disappearance of endemic eusuchians such as Hylaeochampsidae, Allodaposuchus and their close relatives, and non-eusuchians such as Doratodon or Theriosuchus. Despite extensive sampling in Danian continental deposits, only scarce fragmentary crocodylomorph remains have been cited. It is not until the late Paleocene and Eocene that a recovery in continental crocodylomorphs is observed. The presence of taxa such as planocraniids, the alligatoroids Diplocynodon and Hassiacosuchus, and stem crocodyloids during this period provide the first reliable continental records of Crocodylia in Europe and is best explained by post-extinction immigration from Asia or North America. By contrast, marine forms such as Thoracosaurus are found on both sides of the K-Pg boundary in Europe. The adaptation of these marine animals to different environments, from shallow seas to more transitional or fluvial environments, could be the key to their success and survival across the K-Pg boundary, as seen in other marine crocodylomorph clades such as Dyrosauridae.

The Survivors of the Permian Mass Extinction Delayed Benthic Marine Recovery

Competition in slow motion: the unusual case of benthic marine communities in the wake of the end-Permian mass extinction

Authors:

Hautmann et al

Abstract:

Changes of community structure in response to competition usually take place on timescales that are much too short to be visible in the geological record. Here we report the notable exception of a benthic marine community in the wake of the end-Permian mass extinction, which is associated with the microbial limestone facies of the earliest Triassic of South China. The newly reported fauna is well preserved and extraordinarily rich (30 benthic macroinvertebrate species, including the new species Astartella? stefaniae (Bivalvia) and Eucochlis obliquecostata (Gastropoda)) and stems from an environmentally stable setting providing favourable conditions for benthic organisms. Whereas changes in the taxonomic composition are negligible over the observed time interval of 10–100 ka, three ecological stages are identified, in which relative abundances of initially rare species continuously increased at the cost of previously dominant species. Concomitant with the changes of dominant species is an increase in faunal evenness and heterogeneity. In the absence of both environmental and taxonomic changes, we attribute this pattern to the long-term effects of interspecific competition, which acted at an unusually slow pace because the number of competing species and potential immigrants was dramatically reduced by the end-Permian mass extinction. We suggest that these non-actualistic conditions led to decreased rates of niche differentiation and hence to the delayed rediversification of benthos that characterizes the aftermath of the greatest Phanerozoic mass extinction event. A hyperbolic diversification model is proposed, which accounts for the positive relationship between the intensity of interspecific competition and the rate of niche differentiation and resolves the conundrum of delayed rediversification at a time when niche space was largely vacated.

Trace Fossils From Smithian/Spathian Triassic South China Suggest Gradual Biotic Recovery From PT Extinction

Early Triassic trace fossils from the Three Gorges area of South China: Implications for the recovery of benthic ecosystems following the Permian–Triassic extinction

Authors:

Zhao et al

Abstract:

The Lower Triassic Daye and Jialingjiang formations of the Three Gorges area (South China) record the recovery interval of benthic tracemaking invertebrates following the P–Tr mass extinction. A total of 17 ichnospecies in 14 ichnogenera are documented from Smithian and Spathian strata. Our trace fossil data, in combination with previously published studies, show that ichnodiversity in the Middle Yangtze region increased markedly in the early Spathian. Trace fossils in the Smithian are dominated by simple, small, horizontal burrows, including Didymaulichnus and Planolites, whereas Spathian trace fossils are diverse and abundant with moderate–high bioturbation levels and complex burrow networks, such as Thalassinoides. Both burrow sizes and penetration depths increased gradually from the early Spathian to the middle–late Spathian, implying a gradual recovery pattern for benthic ecosystems. Early Triassic ichnofossils are characterised by aspects of opportunistic behaviour (e.g., low-to-moderate ichnodiversity, low-to-moderate bioturbation, small burrow widths, and shallow tiering), suggesting stressed environmental conditions. The recovery tempo and pattern of ichnocoenoses in South China is likely structured by temporal and spatial changes of the refuge zone in the Early Triassic.

Early Triassic Tetrapod Swimming Trace Fossils Left due to PT Extinction Aftershocks?

Swimming reptiles make their mark in the Early Triassic: Delayed ecologic recovery increased the preservation potential of vertebrate swim tracks

Authors:

Thomson et al

Abstract:

Fossil tetrapod swim tracks have been reported from deposits throughout the world, ranging in age from the Carboniferous (Mississippian) to the Neogene (Pleistocene). A normalized analysis of these occurrences demonstrates that lower Triassic strata contain an anomalously high number of occurrences. Lower Triassic swim tracks also tend to be better preserved, showing exceptionally detailed features such as scale striae and crescent-shaped claw margins. Preservation of these features required a firm and semicohesive substrate in order to maintain track detail before and after burial. Swim-track localities from the lower Triassic Moenkopi Formation in Utah (USA) are characterized by sedimentary and trace fossil features that demonstrate the widespread development and persistence of firmground substrates in a large delta plain complex. Within this delta, complex low-diversity invertebrate trace fossil assemblages consist of locally high densities of diminutive, millimeter-scale traces characteristic of stressed brackish-water faunas. We suggest that the depauperate infauna characteristic of such environments was repressed due to delayed biotic recovery following the end-Permian mass extinction, resulting in extremely low intensities of bioturbation. Lack of biogenic mixing promoted semiconsolidation of dewatered mud substrates and the widespread production and persistence of firmgrounds capable of recording and maintaining swim tracks. Thus a combination of factors, unique to the Early Triassic, increased the preservation potential of detailed swim tracks: (1) depositional environments that promoted the production of firmground substrates, (2) delayed ecologic recovery resulting in the lack of well-bioturbated sediment, and (3) the swimming behavior of various Early Triassic tetrapods.

More Information About the Hettangian Jurassic/Post Triassic-Jurassic Mass Extinction Sponge Bob World

Andean sponges reveal long-term benthic ecosystem shifts following the end-Triassic mass extinction

Authors:

Ritterbush et al

Abstract:

Thick cherts and cherty dolomites in the basal Jurassic Aramachay Formation of Peru preserve a thriving continental shelf community dominated by siliceous sponges that followed the end-Triassic collapse of metazoan-rich carbonate accumulation. Similar Hettangian and Sineumurian deposits from Nevada, U.S.A., Austria, and Morocco suggest that an Early Jurassic siliceous sponge takeover was a widespread phenomenon that persisted for ~ 2 m.y. until metazoan-driven carbonate sedimentation recovered. The post-extinction dominance of siliceous sponges likely resulted from the confluence of metazoan carbonate reef collapse (removal of incumbents) and geochemical conditions that fostered the success of the siliceous sponge-dominated ecosystem. Simple mass balance calculations suggest the siliceous sponge takeover was likely permitted by an increased silica flux as a consequence of weathering Central Atlantic Magmatic Province (CAMP) basalts. The CAMP basalts alone could supply all the silica needed to sustain the sponge takeover, although contributions were also likely from increased hot-climate weathering of other silicates and possible reductions in dissolved silica demand by radiolarians. Detailed sedimentological, fossil, and microfacies analyses were conducted at six field sites across a shallow shelf system recorded in the central Peruvian Andes (Yauli Dome), focusing on the metazoan contribution to sedimentation. Sedimentary structures at all six sites demonstrated on-shelf deposition, similar to the underlying upper Triassic Chambará Formation (in contrast to the black shale-rich facies of the Aramachay Formation in other areas of Peru). Examination of up to 147 m of cherty dolomite from the Aramachay Formation revealed a siliceous sponge-dominated ecosystem, including sponge body fossils, compressed in situ sponge materials, and abundant transported spiculite sediments. Siliceous sponges, mostly demosponges and rare hexactinellids, account for the chert lithology and apparently dominated the local ecology for approximately two million years. The role of metazoan biocalcifiers in sediment production and ecological structure was profoundly reduced compared to the under- and overlying formations, representing a clear ecological state shift from pre-extinction carbonate to post-extinction siliceous dominated ecosystems before the carbonate system recovered ~ 2 m.y. after the extinction.

Nothosaurus zhangi: a Very Large Nothosaur From Anisian China's Seas

A gigantic nothosaur (Reptilia: Sauropterygia) from the Middle Triassic of SW China and its implication for the Triassic biotic recovery

Authors:

Liu et al

Abstract:

The presence of gigantic apex predators in the eastern Panthalassic and western Tethyan oceans suggests that complex ecosystems in the sea had become re-established in these regions at least by the early Middle Triassic, after the Permian-Triassic mass extinction (PTME). However, it is not clear whether oceanic ecosystem recovery from the PTME was globally synchronous because of the apparent lack of such predators in the eastern Tethyan/western Panthalassic region prior to the Late Triassic. Here we report a gigantic nothosaur from the lower Middle Triassic of Luoping in southwest China (eastern Tethyan ocean), which possesses the largest known lower jaw among Triassic sauropterygians. Phylogenetic analysis suggests parallel evolution of gigantism in Triassic sauropterygians. Discovery of this gigantic apex predator, together with associated diverse marine reptiles and the complex food web, indicates global recovery of shallow marine ecosystems from PTME by the early Middle Triassic.

Environmental Impacts on Biotic Recovery During the Induan Triassic

Environmental controls on marine ecosystem recovery following mass extinctions, with an example from the Early Triassic

Authors:

Wei et al

Abstract:

The recovery of marine ecosystems following a mass extinction event involves an extended interval of increasing biotic diversity and ecosystem complexity. The pace of recovery may be controlled by intrinsic ecosystem or extrinsic environmental factors. Here, we present an analysis of changes in marine conditions following the end-Permian mass extinction with the objective of evaluating the role of environmental factors in the protracted (~ 5-Myr-long) recovery of marine ecosystems during the Early Triassic. Specifically, our study examines changes in weathering, productivity, and redox proxies in three sections in South China (Chaohu, Daxiakou, and Zuodeng) and one in northern India (Mud). Our results reveal: 1) recurrent environmental perturbations during the Early Triassic; 2) a general pattern of high terrestrial weathering rates and more intensely reducing marine redox conditions during the early Griesbachian, late Griesbachian, mid-Smithian, and (more weakly) the mid-Spathian; 3) increases in marine productivity during the aforementioned intervals except for the early Griesbachian; and 4) stronger and more temporally discrete intervals of environmental change in deepwater sections (Chaohu and Daxiakou) relative to shallow and intermediate sections (Zuodeng and Mud). Our analysis reveals a close relationship between episodes of marine environmental deterioration and a slowing or reversal of ecosystem recovery based on metrics of biodiversity, within-community (alpha) diversity, infaunal burrowing, and ecosystem tiering. We infer that the pattern and pace of marine ecosystem recovery was strongly modulated by recurrent environmental perturbations during the Early Triassic. These perturbations were associated with elevated weathering and productivity fluxes, implying that nutrient and energy flows were key influences on recovery. More regular secular variation in deepwater relative to shallow-water environmental conditions implies that perturbations originated at depth (i.e., within the oceanic thermocline) and influenced the ocean-surface layer irregularly. Finally, we compared patterns of environmental disturbance and ecosystem recovery following the other four “Big Five” Phanerozoic mass extinctions to evaluate whether commonalities exist. In general, the pace of ecosystem recovery depends on the degree of stability of the post-crisis marine environment.

Environmental Impacts During Biotic Recovery After the Permian/Triassic Mass Extinction

Environmental controls on marine ecosystem recovery following mass extinctions, with an example from the Early Triassic

Authors:

Wei et al

Abstract:

The recovery of marine ecosystems following a mass extinction event involves an extended interval of increasing biotic diversity and ecosystem complexity. The pace of recovery may be controlled by intrinsic ecosystem or extrinsic environmental factors. Here, we present an analysis of changes in marine conditions following the end-Permian mass extinction with the objective of evaluating the role of environmental factors in the protracted (~ 5-Myr-long) recovery of marine ecosystems during the Early Triassic. Specifically, our study examines changes in weathering, productivity, and redox proxies in three sections in South China (Chaohu, Daxiakou, and Zuodeng) and one in northern India (Mud). Our results reveal: 1) recurrent environmental perturbations during the Early Triassic; 2) a general pattern of high terrestrial weathering rates and more intensely reducing marine redox conditions during the early Griesbachian, late Griesbachian, mid-Smithian, and (more weakly) the mid-Spathian; 3) increases in marine productivity during the aforementioned intervals except for the early Griesbachian; and 4) stronger and more temporally discrete intervals of environmental change in deepwater sections (Chaohu and Daxiakou) relative to shallow and intermediate sections (Zuodeng and Mud). Our analysis reveals a close relationship between episodes of marine environmental deterioration and a slowing or reversal of ecosystem recovery based on metrics of biodiversity, within-community (alpha) diversity, infaunal burrowing, and ecosystem tiering. We infer that the pattern and pace of marine ecosystem recovery was strongly modulated by recurrent environmental perturbations during the Early Triassic. These perturbations were associated with elevated weathering and productivity fluxes, implying that nutrient and energy flows were key influences on recovery. More regular secular variation in deepwater relative to shallow-water environmental conditions implies that perturbations originated at depth (i.e., within the oceanic thermocline) and influenced the ocean-surface layer irregularly. Finally, we compared patterns of environmental disturbance and ecosystem recovery following the other four “Big Five” Phanerozoic mass extinctions to evaluate whether commonalities exist. In general, the pace of ecosystem recovery depends on the degree of stability of the post-crisis marine environment.

Five Million Years After Permian Extinction Marine Ecosystem More Complex Than Anticipated

Coprolites from the upper Osawa Formation (upper Spathian), northeastern Japan: Evidence for predation in a marine ecosystem 5 Myr after the end-Permian mass extinction

Authors:

Nakajima et al

Abstract:

Lower Triassic marine deposits, which can potentially provide important information on the diversity and trophic structure of marine ecosystems following the end-Permian mass extinction, are rarely exposed in the world. Given the sparse body fossil record from the Lower Triassic, non-body fossil evidences, such as trace fossils for example, may provide additional windows on fossil ecosystems. Herein, the authors recently found dark, amorphous lumps of various sizes, ranging from a few millimetres to approximately 7 cm in maximum dimension, from the offshore marine deposit of upper Osawa Formation (Spathian, Lower Triassic) in the South Kitakami Terrane of northeast Japan. Compared with the surrounding siliciclastic sediments, the lumps are rich in phosphate and organic carbon, and poor in silicates. Shape, mode of occurrence, bone inclusion and geochemical signatures of these lumps confirm that these are coprolites, produced not by benthic sediment feeders, but most likely by nektonic animals. Bone inclusion also suggests that carnivorous fish and/or marine reptiles, constituting the higher part of the food chain, produced at least a part of the specimens. Despite the low diversity of the known fossil vertebrates from the Osawa formation, coprolites first shed light on the predator–prey interactions in the marine ecosystem in South Kitakami Terrane 5 Myr after the end-Permian mass extinction.

Tuatara Relative Survived Through KT/K-Pg Extinction Into Paleogene in South America

The youngest South American rhynchocephalian, a survivor of the K/Pg extinction

Authors:

Apesteguía et al

Abstract:

Rhynchocephalian lepidosaurs, though once widespread worldwide, are represented today only by the tuatara (Sphenodon) of New Zealand. After their apparent early Cretaceous extinction in Laurasia, they survived in southern continents. In South America, they are represented by different lineages of Late Cretaceous eupropalinal forms until their disappearance by the Cretaceous/Palaeogene (K/Pg) boundary. We describe here the only unambiguous Palaeogene rhynchocephalian from South America; this new taxon is a younger species of the otherwise Late Cretaceous genus Kawasphenodon. Phylogenetic analysis confirms the allocation of the genus to the clade Opisthodontia. The new form from the Palaeogene of Central Patagonia is much smaller than Kawasphenodon expectatus from the Late Cretaceous of Northern Patagonia. The new species shows that at least one group of rhynchocephalians not related to the extant Sphenodon survived in South America beyond the K/Pg extinction event. Furthermore, it adds to other trans-K/Pg ectotherm tetrapod taxa, suggesting that the end-Cretaceous extinction affected Patagonia more benignly than the Laurasian landmasses.

Using Mammalian Femora to Discern Paleodiversity Across KT/K-Pg Boundary

Mammalian femora across the Cretaceous–Paleogene boundary in eastern Montana

Authors:

DeBey et al

Abstract:

Our understanding of latest Cretaceous and earliest Paleogene mammalian evolution is based almost entirely on the dental fossil record. Mammalian postcranial fossils are rare and mostly found as isolated elements in latest Cretaceous and earliest Paleogene vertebrate microfossil assemblages of North America. Although placing these fossils in a tooth-based taxonomic framework is difficult, they can provide insight into locomotor diversity and habitat preference to complement diet reconstructions and diversity estimates from dental fossils. Here, we describe 64 femora of mammals recovered from latest Cretaceous (Lancian) and earliest Paleogene (Puercan) localities in eastern Montana. We sorted these based on morphology and size (morphotypes). In some cases, morphotypes were tentatively assigned to dentally based taxa that are known from these strata.

Although our resulting femoral dataset is small relative to the study area's dental dataset, we show several key findings. First, there is a greater morphological diversity of multituberculate femora than previously recognized, especially in the latest Cretaceous sample. In contrast, metatherians, which have a high relative abundance in Lancian Hell Creek Formation dental assemblages, are absent from our postcranial samples; eutherian femora are only present in the Puercan assemblages. Second, we record a minor decrease in morphotype richness across the K–Pg boundary that is associated with an increase in mean specimen size, due to the appearance of a few significantly larger-bodied, immigrant taxa. Among the eutherians, there are two specimens of larger-bodied early Puercan archaic ungulates, a very large specimen of a middle/late Puercan taeniodont, pantodont, or triisodontid, as well as a specimen possibly attributed to a “plesiadapiform” archaic primate. Third, preliminary functional morphologic analyses of the more complete specimens suggest that locomotor diversity increased from mainly arboreal or terrestrial/saltatorial multituberculates in the latest Cretaceous to include a fossorial multituberculate and potentially an arboreal eutherian in the early Paleocene. These patterns parallel those previously reported from a dental dataset and indicate that postcranial data are valuable as an independent means to test hypotheses of taxonomic and ecomorphological diversity across the K–Pg boundary.

Using Vegetation Patterns from the KT/K-Pg Mass Extinction for Comparison

The global vegetation pattern across the Cretaceous–Paleogene mass extinction interval: A template for other extinction events

Authors:

Vajda et al

Abstract:

Changes in pollen and spore assemblages across the Cretaceous–Paleogene (K–Pg) boundary elucidate the vegetation response to a global environmental crisis triggered by an asteroid impact in Mexico 66 Ma. The Cretaceous–Paleogene boundary clay, associated with the Chicxulub asteroid impact event, constitutes a unique, global marker bed enabling comparison of the world-wide palynological signal spanning the mass extinction event. The data from both hemispheres are consistent, revealing diverse latest Cretaceous assemblages of pollen and spores that were affected by a major diversity loss as a consequence of the K–Pg event. Here we combine new results with past studies to provide an integrated global perspective of the terrestrial vegetation record across the K–Pg boundary. We further apply the K–Pg event as a template to asses the causal mechanism behind other major events in Earths history. The end-Permian, end-Triassic, and the K–Pg mass-extinctions were responses to different causal processes that resulted in essentially similar succession of decline and recovery phases, although expressed at different temporal scales. The events share a characteristic pattern of a bloom of opportunistic "crisis" tax followed by a pulse in pioneer communities, and finally a recovery in diversity including evolution of new taxa.

Based on their similar extinction and recovery patterns and the fact that Last and First Appearance Datums associated with the extinctions are separated in time, we recommend using the K–Pg event as a model and to use relative abundance data for the stratigraphic definition of mass-extinction events and the placement of associated chronostratigraphic boundaries.