Signor-Lipps Research Articles

Small populations of Palaeolithic humans in Cyprus hunted endemic megafauna to extinction.

The hypothesized main drivers of megafauna extinctions in the late Quaternary have wavered between over-exploitation by humans and environmental change, with recent investigations demonstrating more nuanced synergies between these drivers depending on taxon, spatial scale, and region. However, most studies still rely on comparing archaeologically based chronologies of timing of initial human arrival into naïve ecosystems and palaeontologically inferred dates of megafauna extinctions. Conclusions arising from comparing chronologies also depend on the reliability of dated evidence, dating uncertainties, and correcting for the low probability of preservation (Signor-Lipps effect). While some models have been developed to test the susceptibility of megafauna to theoretical offtake rates, none has explicitly linked human energetic needs, prey choice, and hunting efficiency to examine the plausibility of human-driven extinctions. Using the island of Cyprus in the terminal Pleistocene as an ideal test case because of its late human settlement (~14.2-13.2 ka), small area (~11 000 km2), and low megafauna diversity (2 species), we developed stochastic models of megafauna population dynamics, with offtake dictated by human energetic requirements, prey choice, and hunting-efficiency functions to test whether the human population at the end of the Pleistocene could have caused the extinction of dwarf hippopotamus (Phanourios minor) and dwarf elephants (Palaeoloxodon cypriotes). Our models reveal not only that the estimated human population sizes (n = 3000-7000) in Late Pleistocene Cyprus could have easily driven both species to extinction within < 1000 years, the model predictions match the observed, Signor-Lipps-corrected chronological sequence of megafauna extinctions inferred from the palaeontological record (P. minor at ~12-11.1 ka, followed by P. cypriotes at ~10.3-9.1 ka).

Calcareous nannofossil distribution in the upper Maastrichtian–lower Thanetian interval in the Izeh zone (Southwest Iran): biostratigraphic framework and stage boundary identification in the Eastern Tethys

The distribution of calcareous nannofossil species in the upper part ofGurpi Formation and lower part of Pabdeh Formation has been investigated in the Karta section (northwest of Izeh in Zagros Basin, Iran, Eastern Tethys) to provide a biostratigraphic framework from Maastrichtian to Thanetian interval. In this study, 31 genera and 52 species of calcareous nannofossils have been identified and based on the recognized bioevents and the resulting biozones, the studied interval spans from the top of the nannofossil zone UC19TP to the base of the NP7 zone and covers ~10.8Myr. In this study, the Gurpi Formation spans from the upper UC19TP to NP4 zones, while the lowest part of Pabdeh Formation covers NP5, NP6 and NP7 zones. The studied sequence is continuous and encompasses Cretaceous-Paleogene (K/Pg), Danian/Selandian and Selandian/Thanetian boundaries. The K/Pg boundary is characterized by nannofossil assemblage recognized worldwide, such as the occurrence of Biantholithus, Cruciplacolithus, Braarudosphaera, Praeprinsius, and calcareous blooms of Thoracosphaera spp. Adecrease in the abundance of nannofossils is observed in the upper part of the Maastrichtian to the lower part of the Danian; poor to moderate preservation of nannofossils and low diversified nannofossil assemblages cover most of the studied samples. Here, as a result of species poor to moderate preservation, we observe patterns of stepwise extinctions upward in the top of CC25 zone, that culminate with the last occurrence of eight species, just prior to the base of the UC20bTP. We interpret these patterns to be mainly the result of diagenetic alteration. Our dataset provides a record over a long-lasting interval of stepwise extinctions toward the K/Pg boundary that was likely caused by the diagenetically-enhanced Signor-Lipps effect.

The earliest occurrence of Equus in South Asia

ABSTRACT Fossil horses are ubiquitous members of late Neogene and Quaternary ecosystems in Eurasia and Africa. The genus Equus is conventionally thought to be a Pleistocene immigrant into Eurasia from North America, and the concurrent appearance of these monodactyl equids in Eurasia around 2.58 Ma is accepted as the Equus Datum. Here, we report on a specimen of Equus found near the village of Jhil, from the latest Pliocene of the Upper Siwaliks of India. The specimen was recovered from sediments that are lithologically equivalent to the Upper Pliocene Saketi Formation, and have been dated paleomagnetically to lie just below the Gauss–Matuyama boundary, therefore, the latest Pliocene. Our comparative work shows that the anatomy of Jhil specimen is consistent with the Early Pleistocene Siwalik horse, Equus sivalensis. Our finding extends the temporal distribution of this species into the latest Pliocene, and adds to our understanding of the variation in this species of horse. We also argue that along with potential latest Pliocene occurrences of Equus from Europe, and accounting for the Signor–Lipps effect, the Equus Datum should be revised as a latest Pliocene event.

Quantifying the middle–late Cambrian trilobite diversity pattern in South China

The middle–late Cambrian is a key interval between the Cambrian Explosion and the Great Ordovician Biodiversification Event (GOBE) that marks a major biologic evolutionary transition in the geologic record. Diversity (i.e. richness) patterns in this interval show that macro-biota experienced evolutionary setbacks for the first time. However, relatively little attention has been paid to this interval in previous macroevolutionary studies and very different conclusions about the diversity patterns in coarse time-resolution have been documented. As a dominate group of marine benthic organisms in the Cambrian, trilobites provide insightful information to understand the history of biodiversity in the Cambrian marine ecosystem from the Cambrian Explosion to the GOBE. South China is a region with relatively good preservation of Cambrian fossil materials and sections, and 4 out of 6 Cambrian GSSPs were established in South China. In this paper, we use constrained optimization (CONOP) to correlate 19 sections from South China to reduce the Signor-Lipps effect and integrate the results with high-resolution chronostratigraphic data to evaluate the middle–late Cambrian trilobite diversity pattern in South China. This study, for the first time, constructs a high time-resolution (about 60 kyr) trilobite species-level richness curve with estimated time from Age 4 to the Paibian. A double-peaked species diversification is separated by a minor extinction in Stage 4; this is followed by a gradual decline of species diversity over the entire Wuliuan Age. A radiation of three times increase of species diversity in the Drumian and Guzhangian is exhibited and the diversity remains high for most of the Guzhangian Stage; this is followed by a great extinction at the end of the Guzhangian with around 50% species lost. Detailed comparison with previous composite studies and fossil material from single sections revealed that the Signor-Lipps effect could produce large biases in diversity pattern. In addition, a precise analysis of species evolution features compared with environmental indices provides a perspective about trilobite evolutionary mechanisms associated with environmental changes related to the carbon cycle and biotic competition.

Stratigraphic signatures of mass extinctions: ecological and sedimentary determinants.

Stratigraphic patterns of last occurrences (LOs) of fossil taxa potentially fingerprint mass extinctions and delineate rates and geometries of those events. Although empirical studies of mass extinctions recognize that random sampling causes LOs to occur earlier than the time of extinction (Signor–Lipps effect), sequence stratigraphic controls on the position of LOs are rarely considered. By tracing stratigraphic ranges of extant mollusc species preserved in the Holocene succession of the Po coastal plain (Italy), we demonstrated that, if mass extinction took place today, complex but entirely false extinction patterns would be recorded regionally due to shifts in local community composition and non-random variation in the abundance of skeletal remains, both controlled by relative sea-level changes. Consequently, rather than following an apparent gradual pattern expected from the Signor–Lipps effect, LOs concentrated within intervals of stratigraphic condensation and strong facies shifts mimicking sudden extinction pulses. Methods assuming uniform recovery potential of fossils falsely supported stepwise extinction patterns among studied species and systematically underestimated their stratigraphic ranges. Such effects of stratigraphic architecture, co-produced by ecological, sedimentary and taphonomic processes, can easily confound interpretations of the timing, duration and selectivity of mass extinction events. Our results highlight the necessity of accounting for palaeoenvironmental and sequence stratigraphic context when inferring extinction dynamics from the fossil record.

Towards better correlation of the Central Paratethys regional time scale with the standard geological time scale of the Miocene Epoch

AbstractDepositional sequences originating in semi-enclosed basins with endemic biota, partly or completely isolated from the open ocean, frequently do not allow biostratigraphic correlations with the standard geological time scale (GTS). The Miocene stages of the Central Paratethys represent regional chronostratigraphic units that were defined in type sections mostly on the basis of biostratigraphic criteria. The lack of accurate dating makes correlation within and between basins of this area and at global scales difficult. Although new geochronological estimates increasingly constrain the age of stage boundaries in the Paratethys, such estimates can be misleading if they do not account for diachronous boundaries between lithostratigraphic formations and for forward smearing of first appearances of index species (Signor-Lipps effect), and if they are extrapolated to whole basins. Here, we argue that (1) geochronological estimates of stage boundaries need to be based on sections with high completeness and high sediment accumulation rates, and (2) that the boundaries should preferentially correspond to conditions with sufficient marine connectivity between the Paratethys and the open ocean. The differences between the timing of origination of a given species in the source area and timing of its immigration to the Paratethys basins should be minimized during such intervals. Here, we draw attention to the definition of the Central Paratethys regional time scale, its modifications, and its present-day validity. We suggest that the regional time scale should be adjusted so that stage boundaries reflect local and regional geodynamic processes as well as the opening and closing of marine gateways. The role of eustatic sea level changes and geodynamic processes in determining the gateway formation needs to be rigorously evaluated with geochronological data and spatially-explicit biostratigraphic data so that their effects can be disentangled.

Estimating the number of pulses in a mass extinction

AbstractThe Signor-Lipps effect states that even a sudden mass extinction will invariably appear gradual in the fossil record, due to incomplete fossil preservation. Most previous work on the Signor–Lipps effect has focused on testing whether taxa in a mass extinction went extinct simultaneously or gradually. However, many authors have proposed scenarios in which taxa went extinct in distinct pulses. Little methodology has been developed for quantifying characteristics of such pulsed extinction events. Here we introduce a method for estimating the number of pulses in a mass extinction, based on the positions of fossil occurrences in a stratigraphic section. Rather than using a hypothesis test and assuming simultaneous extinction as the default, we reframe the question by asking what number of pulses best explains the observed fossil record.Using a two-step algorithm, we are able to estimate not just the number of extinction pulses but also a confidence level or posterior probability for each possible number of pulses. In the first step, we find the maximum likelihood estimate for each possible number of pulses. In the second step, we calculate the Akaike information criterion and Bayesian information criterion weights for each possible number of pulses, and then apply ak-nearest neighbor classifier to these weights. This method gives us a vector of confidence levels for the number of extinction pulses—for instance, we might be 80% confident that there was a single extinction pulse, 15% confident that there were two pulses, and 5% confident that there were three pulses. Equivalently, we can state that we are 95% confident that the number of extinction pulses is one or two. Using simulation studies, we show that the method performs well in a variety of situations, although it has difficulty in the case of decreasing fossil recovery potential, and it is most effective for small numbers of pulses unless the sample size is large. We demonstrate the method using a data set of Late Cretaceous ammonites.

Estimates of the magnitudes of major marine mass extinctions in earth history

Procedures introduced here make it possible, first, to show that background (piecemeal) extinction is recorded throughout geologic stages and substages (not all extinction has occurred suddenly at the ends of such intervals); second, to separate out background extinction from mass extinction for a major crisis in earth history; and third, to correct for clustering of extinctions when using the rarefaction method to estimate the percentage of species lost in a mass extinction. Also presented here is a method for estimating the magnitude of the Signor-Lipps effect, which is the incorrect assignment of extinctions that occurred during a crisis to an interval preceding the crisis because of the incompleteness of the fossil record. Estimates for the magnitudes of mass extinctions presented here are in most cases lower than those previously published. They indicate that only ∼81% of marine species died out in the great terminal Permian crisis, whereas levels of 90-96% have frequently been quoted in the literature. Calculations of the latter numbers were incorrectly based on combined data for the Middle and Late Permian mass extinctions. About 90 orders and more than 220 families of marine animals survived the terminal Permian crisis, and they embodied an enormous amount of morphological, physiological, and ecological diversity. Life did not nearly disappear at the end of the Permian, as has often been claimed.

Accurate and precise estimates of origination and extinction rates

Paleobiologists have used many different methods for estimating rates of origination and extinction. Unfortunately, all equations that consider entire age ranges are distorted by the Pull of the Recent, the Signor-Lipps effect, and simple edge effects. Attention has been paid recently to an equation of Foote's that considers counts of taxa either crossing the bottom and top of an interval or crossing one boundary but not the other. This generalized boundary-crosser (BC) method has important advantages but is still potentially subject to the major biases. The only published equation that circumvents all of them is the three-timer (3T) log ratio, which does so by focusing on a four-interval moving window. Although it is highly accurate it is noisy when turnover rates are very high or sampling is very poor. More precise values are yielded by a newly derived equation that uses the same counts. However, it also considers taxa sampled in a window's first and fourth intervals but missing from the third (i.e., gap-fillers). Simulations show that the 3T, gap-filler (GF), and BC equations yield identical values when sampling and turnover are uniform through time. When applied to Phanerozoic-scale marine animal data, 3T and GF agree well but the BC rates are systematically lower. The apparent reason is that (1) long-ranging but infrequently sampled genera are less likely to be split up by taxonomists and (2) the BC equation overweights taxa with long ranges. Thus, BC rates pertain more to rare genera that are likely to represent large clades whereas GF rates pertain more to actual species-level patterns. Given these results, all published turnover rates based either on genus-level data or on age ranges must be reconsidered because they may reflect taxonomic practices more strongly than the species-level dynamics of interest to biologists.

Quantifying the process and abruptness of the end-Permian mass extinction

Studies of the end-Permian mass extinction have suggested a variety of patterns from a single catastrophic event to multiple phases. But most of these analyses have been based on fossil distributions from single localities. Although single sections may simplify the interpretation of species diversity, they are susceptible to bias from stratigraphic incompleteness and facies control of preservation. Here we use a data set of 1450 species from 18 fossiliferous sections in different paleoenvironmental settings across South China and the northern peri-Gondwanan region, and integrate it with high-precision geochronologic data to evaluate the rapidity of the largest Phanerozoic mass extinction. To reduce the Signor-Lipps effect, we applied constrained optimization (CONOP) to search for an optimal sequence of first and last occurrence datums for all species and generate a composite biodiversity pattern based on multiple sections. This analysis indicates that an abrupt extinction of 62% of species took place within 200 Kyr. The onset of the sudden extinction is around 252.3 Ma, just below Bed 25 at the Meishan section. Taxon turnover and diversification rates suggest a deterioration of the living conditions nearly 1.2 Myr before the sudden extinction. The magnitude of the extinction was such that there was no immediate biotic recovery. Prior suggestions of highly variable, multi-phased extinction patterns reflect the impact of the Signor-Lipps effect and facies-dependent occurrences, and are not supported following appropriate statistical treatment of this larger data set.

Fair Sampling of Taxonomic Richness and Unbiased Estimation of Origination and Extinction Rates

Paleobiologists are reaching a consensus that biases in diversity curves, origination rates, and extinction rates need to be removed using statistical estimation methods. Diversity estimates are biased both by methods of counting and by variation in the amount of fossil data. Traditional counts are essentially tallies of age ranges. Because these counts are distorted by interrelated factors such as the Pull of the Recent and the Signor-Lipps effect, counts of taxa actually sampled within intervals should be used instead. Sampling intensity biases can be addressed with randomized subsampling of data records such as individual taxonomic occurrences or entire fossil collections. Fair subsampling would yield taxon counts that track changes in the species pool size, i.e., the diversity of all taxa that could ever be sampled. Most of the literature has overlooked this point, having instead focused on making sample sizes uniform through methods such as rarefaction. These methods flatten the data, undersampling when true diversity is high. A good solution to this problem involves the concept of frequency distribution coverage: a taxon's underlying frequency is said to be “covered” when it is represented by at least one fossil in a data set. A fair subsample, but not a uniform one, can be created by drawing collections until estimated coverage reaches a fixed target (i.e., until a “shareholder quorum” is attained). Origination and extinction rates present other challenges. For many years they were thought of in terms of simple counts or ratios, but they are now treated as exponential decay coefficients of the kind featuring in simple birth-death models. Unfortunately, these instantaneous rates also suffer from counting method biases (e.g., the Pull of the Recent). Such biases can be removed by only examining taxa sampled twice consecutively, three times consecutively, or in the first and third of three intervals but not the second (i.e., two timers, three timers, and part timers). Two similar equations involving these counts can be used. Alternative methods of estimating diversity and turnover through extrapolation share some of the advantages of quorum subsampling and two-timer family equations, but it remains to be shown whether they produce precise and accurate estimates when applied to fossil data.

The latest Permian mass extinction in the Alborz Mountains (North Iran)

AbstractThe Elikah River section in the Alborz Mountains (North Iran) is a fossiliferous, continuous, marine section spanning the Permian–Triassic (P–T) boundary interval. Sixty‐eight taxa of brachiopods, foraminifers and algae have been collected bed‐by‐bed from the topmost 36 m of the Nesen Formation and the basal 2 m of the Elikah Formation, across the P–T boundary that is located in the basal metre of the latter formation. Forty‐six of these taxa from 62 samples have been considered for statistical analyses to unravel the pattern of extinction. First, their range extensions have been determined, which should be added to the highest stratigraphic occurrence of each taxon to identify the extinction level within a certain confidence interval (95%). Then the pattern of the extinction has been analysed, plotting the stratigraphic abundance versus last occurrence below the extinction horizon. The resulting pattern is of a sudden extinction occurring 30 cm below the biostratigraphically defined base of the Triassic. The confidence interval (95%) for the mass extinction is 30 cm thick. As predicted by the ‘Signor–Lipps effect’, brachiopod last occurrences underestimate the time of extinction, as their abundance is below 15%. Therefore, also in North Iran located at equatorial palaeolatitudes along the southern shore of the Palaeotethys Ocean, the pattern of the latest Permian mass extinction is abrupt as observed in South China, in peri‐Gondwana and in the Southern Alps. One of the most plausible mechanisms of the latest Permian sudden mass extinction could have been the emissions of tholeiitic magmas (Siberian Traps), which could have caused greenhouse gases emission into the atmosphere and thus global warming and ozone depletion, triggering the crisis (Svensen et al. 2008). Copyright © 2010 John Wiley &amp; Sons, Ltd.

New range data for marine invertebrate species across the early Toarcian (Early Jurassic) mass extinction

Abstract: We have reinvestigated the marine mass extinction interval that occurred during the early Toarcian, which was a time of widespread marine anoxia. The ranges of marine benthic invertebrates are significantly altered using new observations from the Cleveland Basin, UK. Goniomya rhombifera is reported for the first time from the Whitby Mudstone Formation and together with an increased epifaunal bivalve diversity indicates a brief, relatively oxygenated period towards the end of the event. The new data, together with published results, suggest three apparent extinction horizons on a global scale; the first is just above the Pliensbachian–Toarcian boundary, and the following two are in the semicelatum ammonite Subzone. As a result of the Signor–Lipps effect there may be only one, or possibly two, true extinctions. The youngest extinction horizon coincides with the first of the abrupt carbon isotope shifts that characterize this interval, and with increases in sea surface temperature, continental weathering rates, and seawater anoxia. Pseudomytiloides dubius is the only abundant benthic macroinvertebrate during the most hostile environmental conditions but it and all other benthic species are almost entirely absent for many thousands of years immediately after each abrupt negative carbon isotope shift. Supplementary material: A compilation of the Late Pliensbachian and Early Toarcian marine biotic changes and a discussion of the systematics of the key faunal elements are available at http://www.geolsoc.org.uk/SUP18353 .

Confidence intervals for pulsed mass extinction events

Many authors have proposed scenarios for mass extinctions that consist of multiple pulses or stages, but little work has been done on accounting for the Signor-Lipps effect in such extinction scenarios. Here we introduce a method for computing confidence intervals for the time or stratigraphic distance separating two extinction pulses in a pulsed extinction event, taking into account the incompleteness of the fossil record. We base our method on a flexible likelihood ratio test framework that is able to test whether the fossil record is consistent with any extinction scenario, whether simultaneous, pulsed, or otherwise. As an illustration, we apply our method to a data set on marine invertebrates from the Permo-Triassic boundary of Meishan, China. Using this data set, we show that the fossil record of ostracodes and that of brachiopods are each consistent with simultaneous extinction, and that these two extinction pulses are separated by 720,000 to 1.2 million years with 95% confidence. With appropriate data, our method could also be applied in other situations, such as tests of origination patterns, coordinated stasis, and recovery after a mass extinction.

EXTINCTION, SURVIVAL, AND RECOVERY OF LAGENIDE FORAMINIFERS IN THE PERMIAN–TRIASSIC BOUNDARY INTERVAL, CENTRAL TAURIDES, TURKEY

The assemblage of lagenide foraminifers in uppermost Permian rocks of the central Taurides consists of 22 species in 16 genera, including the new species Rectostipulina pentamerata, plus additional unidentified elements. Of these, only two identifiable species in “Nodosaria” and indeterminate syzraniids survived the end-Permian mass extinction. The last occurrences of most taxa fall within the upper half-meter of the Permian System, a pattern consistent with abrupt extinction when tested for the Signor-Lipps effect. Permian survivors are joined locally in the Lower Triassic and lower Middle Triassic by three additional species. Globally, lagenide species diversity remained low until latest Anisian time, and probably did not reach pre-extinction levels until Late Triassic or Early Jurassic time. The survival of the lagenide clade, in contrast to the complete elimination of fusulinoidean fusulinides, may be linked to the lagenides' comparatively greater paleoenvironmental tolerances and wider paleogeographic distribution. Evaluation of lagenide extinction and survival across the Permian–Triassic boundary in the central Taurides is complicated by a facies change from bioclastic wackestones and packstones to oolitic grainstones near the top of the Permian, and by the development of variably dolomitized and pyritic stromatolites and overlying oolites in the lowest Triassic. The stromatolitic and oolitic Lower Triassic lithologies represent a sedimentologic response to the end-Permian mass extinction and unusual Early Triassic marine environments. Stromatolites likely became established as disaster forms in an ecologically permissive period that lacked normal marine grazing and bioturbating benthos. Their calcification and preservation may have been promoted by high carbonate saturation levels. Oolites, which are found in recurring facies associations with stromatolites and other anachronistic carbonates in Lower Triassic rocks throughout the Tethyan embayment, probably also formed in response to elevated saturation levels and the absence of a skeletal sink for carbonate.

Interpreting bioevents: What exactly did happen to planktonic foraminifers across the Cretaceous–Tertiary boundary?

The fossil record is the only evidence for the history of life on earth, but suffers from serious biases. The Signor–Lipps and Jaanusson effects are universal in the fossil record and distort patterns of biotic turnover more seriously the more incomplete the record. Hiatuses may also distort the record. The Cretaceous–Tertiary boundary (KTB) is the best global time plane in the entire rock record. The distinctive boundary clay corresponds to a major biotic turnover and occurs globally. Its base is a fall-out deposit that may be the same age worldwide to within a year. Thus the KTB is the best place in the fossil record to test the reliability of patterns of biotic turnover. The record of planktonic foraminifers across the KTB is controversial as regards the timing (sudden versus gradual) and severity (proportion of surviving species) of their extinction. The timing is affected by the Signor–Lipps Effect (SLE). A new technique is presented to compensate quantitatively for the SLE, which shows that the decline in diversity of planktonic foraminifers across the KTB at El Kef started before the boundary, but the SLE accounts for half the observed decline. As regards severity, probabilistic stratigraphy is the best technique to distinguish Cretaceous survivors from reworked specimens and suggests that at maximum 22% of Cretaceous planktonic foraminifers survived the boundary, 11% survived into zone P1a. The ‘Hiatus Effect’ is more imaginary than real, but can be investigated by computer simulation.

The quality of the fossil record and the accuracy of phylogenetic inferences about sampling and diversity.

Because phylogenies can be estimated without stratigraphic data and because estimated phylogenies also infer gaps in sampling, some workers have used phylogeny estimates as templates for evaluating sampling from the fossil record and for "correcting" historical diversity patterns. However, it is not known how sampling intensity (the probability of sampling taxa per unit time) and completeness (the proportion of taxa sampled) affect the accuracy of phylogenetic inferences, nor how phylogenetically inferred estimates of sampling and diversity respond to inaccurate estimates of phylogeny. Both issues are addressed with a series of simulations using simple models of character evolution, varying speciation patterns, and various rates of speciation, extinction, character change, and preservation. Parsimony estimates of simulated phylogenies become less accurate as sampling decreases, and inaccurate trees chronically underestimate sampling. Biotic factors such as rates of morphologic change and extinction both affect the accuracy of phylogenetic estimates and thus affect estimated gaps in sampling, indicating that differences in implied sampling need not reflect actual differences in sampling. Errors in inferred diversity are concentrated early in the history of a clade. This, coupled with failure to account for true extinction times (i.e., the Signor-Lipps effect), inflates relative diversity levels early in clade histories. Because factors other than differences in sampling predict differences in the numbers of gaps implied by phylogeny estimates, inferred phylogenies can be misleading templates for evaluating sampling or historical diversity patterns.

Evidence for abrupt latest Permian mass extinction of foraminifera: Results of tests for the Signor-Lipps effect: Comment and Reply

Research Article| April 01, 1999 Evidence for abrupt latest Permian mass extinction of foraminifera: Results of tests for the Signor-Lipps effect: Comment and Reply Paul B. Wignall; Paul B. Wignall 1School of Earth Sciences, University of Leeds, Leeds, LS2 9JT, UK Search for other works by this author on: GSW Google Scholar Michael R. Rampino Michael R. Rampino 2Earth & Environmental Sciences Program, New York University, 100 Washington Square East, New York, New York 10003, USA and NASA, Goddard Institute for Space Studies, 2880 Broadway, New York, New York 10025, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Paul B. Wignall 1School of Earth Sciences, University of Leeds, Leeds, LS2 9JT, UK Michael R. Rampino 2Earth & Environmental Sciences Program, New York University, 100 Washington Square East, New York, New York 10003, USA and NASA, Goddard Institute for Space Studies, 2880 Broadway, New York, New York 10025, USA Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1999) 27 (4): 383–384. https://doi.org/10.1130/0091-7613(1999)027<0383:EFALPM>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Paul B. Wignall, Michael R. Rampino; Evidence for abrupt latest Permian mass extinction of foraminifera: Results of tests for the Signor-Lipps effect: Comment and Reply. Geology 1999;; 27 (4): 383–384. doi: https://doi.org/10.1130/0091-7613(1999)027<0383:EFALPM>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract No Abstract Available. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Evidence for abrupt latest Permian mass extinction of foraminifera: Results of tests for the Signor-Lipps effect

We used published biostratigraphic data on ranges of fusulinids and other foraminifera from Permian-Triassic boundary sections in the southern Alps, Italy, to test the effects of sampling and species abundance on the record of the timing of the latest Permian extinction. The number of last occurrences of taxa reaches a maximum close to the local base of the Tesero horizon of the Werfen Formation. Taxa that have ≤15% stratigraphic abundance (percent of sample intervals in which a taxon occurs) show last occurrences well before that level, whereas taxa with more complete records tend to disappear at or close to that level. These results are in agreement with simulations for abrupt extinctions, as opposed to gradual or steplike extinction scenarios, and support predictions of the Signor-Lipps effect, that errors in the end points of biostratigraphic ranges can produce range truncations and apparent gradual decline preceding a sudden extinction boundary. On the basis of estimated sedimentation rates for the Italian sections, the end-Permian extinctions could have been very sudden (≤30 k.y.), and the disappearance of most latest Permian foraminifers was most likely coincident with a worldwide ecological stress event, identified by a global negative δ 13 C anomaly that occurs in Italy near the base or within the time-transgressive Tesero horizon.

After the Fall: Lessons and Directions from the K/T Debate

The Alvarez Hypotheses of 1980, that the earth was hit by a large asteroid or comet 65 million years ago, and that the environmental effects stemming from that impact event brought about the K/T mass extinction, are now accepted by a majority of earth scientists. The questions is, then, what next for paleontological extinction research? I propose that the following topics be explored: 1) Better research on actual killing mechanisms. 2) Deciphering multiple causes. 3) Calibrating the Kill Curve of Raup (1990, 1991) relating impact (or crater) size and degree of mass extinction. 4) Following up on disparate extinction hypotheses. 5) Improving sampling methodology, and using some of the lessons or methodologies developed during the K/T debate: (The Signor-Lipps effect, confidence intervals and increased sampling precision or blind sampling programs) on other extinction boundaries. 6) Understanding selectivity: which species live, die, and why. 7) Improving the study of modern day biodiversity by giving it some history, with the goal of understanding the following question: have we entered a new mass extinction episode?