Extinction and quiescence in marine animal genera

ArticleinPaleobiology 33(2):261-272 · March 2007with 12 Reads
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Abstract
If last appearances of marine animal genera are taken as reasonable proxies for true extinctions, then there is appreciable global extinction in every stage of the Phanerozoic. If, instead, backsmearing of extinctions by incomplete sampling is explicitly taken into consideration, a different view of extinction emerges, in which the pattern of extinction is much more volatile and in which quiescent time spans—with little or no global extinction for several million years—are punctuated by major extinction events that are even more extreme than is generally thought. Independent support for this alternative view comes from analysis of genus occurrence data in the Paleobiology Database, which agrees with previous estimates of sampling probability and implies that offsets between extinction and last appearance of one or more stages are quite probable.

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    • Roger A Cooper
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    Copyright - GeoRef, Copyright 2012, American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom, Date revised - 2012-01-01, Language of summary - English, Number of references - 66, Pages - 105-122, ProQuest ID - 919643578, Document feature - illus. incl. 4 tables, SubjectsTermNotLitGenreText - Australasia; biodiversity; biologic evolution; Bivalvia; Cenozoic; extinction; fossil record; Gastropoda; Invertebrata; marine environment; Mollusca; New Zealand; paleoenvironment; probability; Scaphopoda; shelf environment; speciation; statistical analysis, SuppNotes - Includes appendix, Last updated - 2012-06-07, CODEN - GSLSBW, Corporate institution author - Crampton, James S; Foote, Michael; Cooper, Roger A; Beu, Alan G; Peters, Shanan E, DOI - 2012-021007; 0305-8719; GSLSBW
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    • Kevin Padian
    Synopsis: To understand our present diversity crisis, it is natural to look to past crises for parallels and indicators. This is difficult because the present crisis is unlike the "Big Five" of the past: it is mostly terrestrial (with an increasing marine component), involves widespread habitat destruction and alteration of climate, and is largely anthropogenic, with confounding effects of differences in loss of diversity among continents and the difficulty of separating anthropogenic extinctions from natural Pleistocene and post-Pleistocene extinctions. In contrast, the "Big Five" crises of the geologic record are mainly marine (in the first two, no land vertebrates existed), and because marine taxa outnumber terrestrial taxa by a margin of about 25:1, global analyses of diversity crises have tended to lump together all phyla and environments. As a result, terrestrial evidence has been "swamped" statistically by the marine data. Both synchroneity and causality of terrestrial and marine events have usually been assumed, but without decisive data. Terrestrial vertebrate faunas do not seem to have been suddenly and catastrophically affected at the ends of the Permian, the Triassic, and the Cretaceous; rather, the pattern generally seems to be of steady turnover and replacement of groups and sometimes of slow decline.Here I suggest a revision of the concept of "mass extinction," which has no definitional limits on the application of the term with respect to duration, geography, ecology, or taxa affected. Unusual drops in taxonomic diversity have traditionally focused on increases in extinction rates, with scarce consideration of origination rates and their interplay with extinction rates. Analyses of hypothesized diversity crises should be operationally and situationally defined and statistically normalized through the histories of taxa and biotas, and should explicitly include both origination and extinction rates. The term "mass extinctions" would be usefully replaced by "diversity crises." These parameters require not absolute numerical (or percentage) limits but situational ones.
  • Article
    • Dmitry A. Ruban
    Phanerozoic evolution of brachiopods produced many linear (established by a comparison of successive geologic time units) and non-linear (established by a comparison of non-successive geologic time units) effects, which can be examined quantitatively by using the similarity coefficients (Czekanowski's Quantified Coefficient and Gower Index) and correlation tools. The high-rank suprageneric diversity structure accounts for a number of superfamilies in each of 26 orders for every epoch of geological time. The intensity of turnovers in this structure was generally low during the entire Phanerozoic. It was slightly stronger during the Early Paleozoic, but close to zero during the Cenozoic, when the high-rank suprageneric diversity structure of brachiopods stabilized finally. Significant turnovers took place at the Middle Cambrian–Early Ordovician, the Late Ordovician–Early Silurian, the Late Silurian–Early Devonian, the Middle Devonian–Mississippian, and the Permian–Triassic transitions. Influences of mass extinctions, both major like those End Ordovician or Permian/Triassic and minor like Early Jurassic or Jurassic/Cretaceous, on the high-rank suprageneric diversity structure of brachiopods is registered. The strongest was the consequences of the Permian/Triassic catastrophe, which perhaps even reset the brachiopod evolution. No evident direct relationships are established between intensity of turnovers and eustatic fluctuations. However, the changes in the diversity structure recorded with the Gower Index provide evidence that eustatic lowstands were more favorable for intensification in these changes.
  • Article
    Full-text available
    • Jonathan Louis Payne
      Jonathan Louis Payne
    • Sarah Truebe
      Sarah Truebe
    • Ellen Chang
      Ellen Chang
    Ecological theory predicts an inverse association between population size and extinction risk, but most previous paleontological studies have failed to confirm this relationship. The reasons for this discrepancy between theory and observation remain poorly understood. In this study, we compiled a global database of gastropod occurrences and collection-level abundances spanning the Early Permian through Early Jurassic (Pliensbachian). Globally, the database contains 5469 occurrences of 496 genera and 2156 species from 839 localities. Within the database, 30 collections distributed across seven stages contain at least 75 specimens and ten genera—our minimum criteria for within-collection analysis of extinction selectivity. We use logistic regression analysis, based on global and local measures of population size and stage-level extinction patterns in Early Permian through Early Jurassic marine gastropods, to assess the relationship between abundance and extinction risk. We find that global genus occurrence frequency is inversely associated with extinction risk (i.e., positively associated with survival) in 15 of 16 stages examined, statistically significantly so in five stages. Although correlation between geographic range and occurrence frequency may account for some of this association, results from multivariable regression analysis suggest that the association between occurrence frequency and extinction risk is largely independent of geographic range. Within local assemblages, abundance (number of individuals) is also inversely associated with extinction risk. The strength of association is consistent across time and modes of fossil preservation. Effect strength is poorly constrained, particularly in analyses of local collections. In addition to limited power due to small sample size, this poor constraint may result from confounding by ecological variables not controlled for in the analyses, by taphonomic or collection biases, or from non-monotonic relationships between abundance and extinction risk. Two factors are likely to account for the difference between our results and those of most previous studies. First, many previous studies focused on the end-Cretaceous mass extinction event; the extent to which these results can be generalized to other intervals remains unclear. Second, previous findings of nonselective extinction could result from insufficient statistical power rather than the absence of an underlying effect, because nonselective extinction is generally used as the null hypothesis for statistical convenience. Survivorship patterns in late Paleozoic and early Mesozoic gastropods suggest that abundance has been a more important influence on extinction risk through the Phanerozoic than previously appreciated.
  • Chapter
    • Maria Dornelas
      Maria Dornelas
    • Candan Soykan
      Candan Soykan
    • K.I. Ugland
  • Article
    • Dmitry A. Ruban
    A long-term eustatic cycle (fall and subsequent rise of the global sea level) embraced the late Silurian-Middle Devonian time interval. Potentially, these sea-level changes could drive global biodiversity. The stratigraphic ranges of 204 bivalve genera and 279 gastropod genera included into the famous Sepkoski database allow reconstructing changes in the total diversity and the number of originations and extinctions of these important groups of marine benthic macro- -invertebrates during this interval. None of the recorded parameters coincided with the long-term global sea-level cycle. It cannot be not excluded, however, that the global sea-level changes did not affect the regions favourable for bivalve and gastropod radiation because of regional tectonic mechanisms; neither can it be excluded that the eustatic control persisted together with many other extrinsic and intrinsic controls. Interestingly, the generic diversity of gastropods increased together with a cooling trend, and vice versa. Additionally, the Ludlow, Eifelian, and Givetian biotic crises affected, probably, both fossil groups under study. There was also a coincidence of the relatively high bivalve generic diversity, initial radiation of gastropods and the entire biota, and the diversification of brachiopods with the Early Devonian global sea-level lowstand, and this may be interpreted as evidence of a certain eustatic control on the marine biodiversity.
  • Article
    • Matt Friedman
      Matt Friedman
    • Lauren Sallan
      Lauren Sallan
    Fishes include more than half of all living animals with backbones, but large-scale palaeobiological patterns in this assemblage have not received the same attention as those for terrestrial vertebrates. Previous surveys of the fish record have generally been anecdotal, or limited either in their stratigraphic or in their taxonomic scope. Here, we provide a broad overview of the Phanerozoic history of fish diversity, placing a special emphasis on intervals of turnover, evolutionary radiation, and extinction. In particular, we provide in-depth reviews of changes during, and ecological and evolutionary recovery after, the end-Devonian (Hangenberg) and Cretaceous–Palaeogene (K–Pg) extinctions.
  • Article
    • John Alroy
    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.
  • Article
    • Steven M. Stanley
    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.
  • Article
    • James T Boyle
      James T Boyle
    Although extinction risk has been found to have a consistent negative relationship with geographic range across wide temporal and taxonomic scales, the effect has been difficult to disentangle from factors such as sampling, ecological niche, or clade. In addition, studies of extinction risk have focused on benthic invertebrates with less work on planktic taxa. We employed a global set of 1114 planktic graptolite species from the Ordovician to lower Devonian to analyze the predictive power of species’ traits and abiotic factors on extinction risk, combining general linear models (GLMs), partial least-squares regression (PLSR), and permutation tests. Factors included measures of geographic range, sampling, and graptolite-specific factors such as clade, biofacies affiliation, shallow water tolerance, and age cohorts split at the base of the Katian and Rhuddanian stages. The percent variance in durations explained varied substantially between taxon subsets from 12% to 45%. Overall commonness, the correlated effects of geographic range and sampling, was the strongest, most consistent factor (12–30% variance explained), with clade and age cohort adding up to 18% and other factors <10%. Surprisingly, geographic range alone contributed little explanatory power (<5%). It is likely that this is a consequence of a nonlinear relationship between geographic range and extinction risk, wherein the largest reductions in extinction risk are gained from moderate expansion of small geographic ranges. Thus, even large differences in range size between graptolite species did not lead to a proportionate difference in extinction risk because of the large average ranges of these species. Finally, we emphasize that the common practice of determining the geographic range of taxa from the union of all occurrences over their duration poses a substantial risk of overestimating the geographic scope of the realized ecological niche and, thus, of further conflating sampling effects on observed duration with the biological effects of range size on extinction risk.
  • Article
    Full-text available
    • Corentin Gibert
      Corentin Gibert
    • Gilles Escarguel
      Gilles Escarguel
    Estimating biodiversity and its variations through geologic time is a notoriously difficult task, due to several taphonomic and methodological effects that make the reconstructed signal potentially distinct from the unknown, original one. Through a simulation approach, we examine the effect of a major, surprisingly still understudied, source of potential disturbance: the effect of time discretization through biochronological construction, which generates spurious coexistences of taxa within discrete time intervals (i.e., biozones), and thus potentially makes continuous- and discrete-time biodiversity curves very different. Focusing on the taxonomic-richness dimension of biodiversity (including estimates of origination and extinction rates), our approach relies on generation of random continuous-time richness curves, which are then time-discretized to estimate the noise generated by this manipulation. A broad spectrum of data-set parameters (including average taxon longevity and biozone duration, total number of taxa, and simulated time interval) is evaluated through sensitivity analysis. We show that the deteriorating effect of time discretization on the richness signal depends highly on such parameters, most particularly on average biozone duration and taxonomic longevity because of their direct relationship with the number of false coexistences generated by time discretization. With several worst-case but realistic parameter combinations (e.g., when relatively short-lived taxa are analyzed in a long-ranging biozone framework), the original and time-discretized richness curves can ultimately show a very weak to zero correlation, making these two time series independent. Based on these simulation results, we propose a simple algorithm allowing the back-transformation of a discrete-time taxonomic-richness data set, as customarily constructed by paleontologists, into a continuous-time data set. We show that the reconstructed richness curve obtained this way fits the original signal much more closely, even when the parameter combination of the original data set is particularly adverse to an effective time-discretized reconstruction.
  • Article
    Full-text available
    • Nan Crystal Arens
      Nan Crystal Arens
    • Ian D. West
    Previous discussions of mass extinction mechanisms generally focused on circumstances unique to each event. However, some have proposed that extensive volcanism combined with bo- lide impact may offer a general mechanism of mass extinction. To test this hypothesis we compared generic extinction percentages for 73 stages or substages of the Mesozoic and Cenozoic. We found that the highest frequency of intervals with elevated extinction occurred when continental flood basalt volcanism and bolide impact co-occurred. In contrast, neither volcanism nor impact alone yielded statistically elevated extinction frequencies. Although the magnitude of extinction was un- correlated with the size of the associated flood basalt or impact structure, crater diameter did cor- relate with extinction percentage when volcanism and impact coincided. Despite this result, case- by-case analysis showed that the volcanism-impact hypothesis alone cannot explain all intervals of elevated extinction. Continental flood volcanism and impact share important ecological features with other proposed extinction mechanisms. Impacts, like marine anoxic incursions, are pulse dis- turbances that are sudden and catastrophic, and cause extensive mortality. Volcanism, like climate and sea level change, is a press disturbance that alters community composition by placing multi- generational stress on ecosystems. We propose that the coincidence of press and pulse events, not merely volcanism and impact, is required to produce the greatest episodes of dying in Phanerozoic history.
  • Article
    Full-text available
    • Sean Richard Connolly
      Sean Richard Connolly
    • Arnold I. Miller
    During the Ordovician Radiation, domination of benthic marine communities shifted away from trilobites, toward articulate brachiopods, and, to a lesser degree, toward bivalves and gastropods. In this paper, we identify the patterns in origination and extinction probabilities that gave rise to these transitions. Using methods adapted from capture-mark-recapture (CMR) pop-ulation studies, we estimate origination, extinction, and sampling probabilities jointly to avoid con-founding patterns in turnover rates with temporal variation in the quality of the fossil record. Not surprisingly, higher extinction probabilities in trilobites relative to articulate brachiopods, bivalves, and gastropods were partly responsible for relative decreases in trilobite diversity. However, ar-ticulate brachiopods also had higher origination probabilities than trilobites, indicating that rela-tive increases in articulate brachiopod diversity would have occurred even in the absence of be-tween-class differences in extinction probabilities. This contrasts with inferences based on earlier Phanerozoic-scale, long-term averages of turnover probabilities, and it indicates that a major cause of this faunal transition has been overlooked.
  • Article
    • Sean Richard Connolly
      Sean Richard Connolly
    • AI Miller
    During the Ordovician Radiation, domination of benthic marine communities shifted away from trilobites, toward articulate brachiopods, and, to a lesser degree, toward bivalves and gastropods. In this paper, we identify the patterns in origination and extinction probabilities that gave rise to these transitions. Using methods adapted from capture-mark-recapture (CMR) population-studies, we estimate origination, extinction, and sampling probabilities jointly to avoid confounding patterns in turnover rates with temporal variation in the quality of the fossil record. Not surprisingly, higher extinction probabilities in trilobites relative to articulate brachiopods, bivalves, and gastropods were partly responsible for relative decreases in. trilobite diversity. However, articulate brachiopods also had higher origination probabilities than trilobites, indicating that relative increases in articulate brachiopod diversity would have occurred even in the absence of between-class differences in extinction probabilities. This contrasts with inferences based on earlier Phanerozoic-scale, long-term averages of turnover probabilities, and it indicates that a major cause of this faunal transition has been overlooked.
  • Article
    • J.F. Quinn
    • David M. Raup
    • J.J. Sepkoski Jr
    • S.M. Stigler
  • Article
    Full-text available
    • Norman Macleod
      Norman Macleod
    • Peter Rawson
      Peter Rawson
    • P. L. Forey
    • Jeremy R. Young
      Jeremy R. Young
    Mass extinctions are recognized through the study of fossil groups across event horizons, and from analyses of long-term trends in taxonomic richness and diversity. Both approaches have inherent flaws, and data that once seemed reliable can be readily superseded by the discovery of new fossils and/or the application of new analytical techniques. Herein the current state of the Cretaceous–Tertiary (K–T) biostratigraphical record is reviewed for most major fossil clades, including: calcareous nannoplankton, dinoflagellates, diatoms, radiolaria, foraminifera, ostracodes, scleractinian corals, bryozoans, brachio-pods, molluscs, echinoderms, fish, amphibians, reptiles and terrestrial plants (macrofossils and palynomorphs). These reviews take account of possible biasing factors in the fossil record in order to extract the most comprehensive picture of the K–T biotic crisis available. Results suggest that many faunal and floral groups (ostracodes, bryozoa, ammonite cephalopods, bivalves, archosaurs) were in decline throughout the latest Maastrichtian while others (diatoms, radiolaria, benthic foraminifera, brachiopods, gastropods, fish, amphibians, lepidosaurs, terrestrial plants) passed through the K–T event horizon with only minor taxonomic richness and/or diversity changes. A few microfossil groups (calcareous nannoplankton, dinoflagellates, planktonic foraminifera) did experience a turnover of varying magnitudes in the latest Maastrichtian–earliest Danian. However, many of these turnovers, along with changes in ecological dominance patterns among benthic foraminifera, began in the latest Maastrichtian. Improved taxonomic estimates of the overall pattern and magnitude of the K–T extinction event must await the development of more reliable systematic and phylogenetic data for all Upper Cretaceous clades.
  • Article
    Full-text available
    • Samuel A. Bowring
    • Douglas Erwin
      Douglas Erwin
    It is now possible to routinely determine the age of 200-600-m.y.old volcanic rocks interlayered with fossil-bearing deposits to uncertainties of less than 1 m.y. with uranium-lead zircon geochronology. This level of precision, coupled with the recognition that volcanic ash beds are much more common in fossiliferous rocks that previosuly realized, opens new opportunitites for the study of evolutionary rates in deep time. It is now possible to constrain rates of evolutionary radiations, mass extinctions, and other evolutionary events as well as evaluate potentially diachronous biostratigraphic boundaires. For example, a combination of detailed biostratigraphic and chemostratigraphic data with new U-Pb zircon dates for the late Neoproterozoic and Early Cambrian has demonstrated that the soft-bodied Ediacaran fossils immediately underlie the Cambrian, that the base of the Cambrian is much younger than previously recognized, and that the Cambrian explosion lasted 10 m.y. or less. Other recent studies have shown the Middle and Late Cambrian each lasted only about 10 m.y. suggesting that the duration often included trilobite zones was similar to those of Jurassic ammonites. Recent data from the Late Perman and ealiest Triassic of South China now constrain the duration of the most profound mass extintion in the history of life to less than 1 m.y. Collaboration between paleontologists and geochronologists offers the prospect of accurately assessing the rates of evolutionary processes, from speciation to evolutionary radiations and mass extinctions, throughout the Phanerozoic.
  • Article
    • D M Raup
    The dramatic increase in our knowledge of large-body impacts that have occurred in Earth's history has led to strong arguments for the plausibility of meteorite impact as a cause of extinction. Proof of causation is often hampered, however, by our inability to demonstrate the synchronism of specific impacts and extinctions. A central problem is range truncation: the last reported occurrences of fossil taxa generally underestimate the true times of extinction. Range truncation, because of gaps in sedimentation, lack of preservation, or lack of discovery, can make sudden extinctions appear gradual and gradual extinctions appear sudden. Also, stepwise extinction may appear as an artefact of range truncation. These effects are demonstrated by experiments performed on data from field collections of Cretaceous ammonities from Zumaya (Spain). The challenge for future research is to develop a new calculus for treating biostratigraphic data so that fossils can provide more accurate assessments of the timing of extinctions.
  • Article
    • Felix Gradstein
      Felix Gradstein
    • James Ogg
      James Ogg
    • A.G. Smith
    A successor to A Geologic Time Scale 1989 (Cambridge, 1990), this volume introduces the theory and methodology behind the construction of the new time scale, before presenting the scale itself in extensive detail. An international team of over forty stratigraphic experts develops the most up-to-date international stratigraphic framework for the Precambrian and Phanerozoic eras. A large wallchart (not available for eBook) summarizing the time scale at the back of the book completes this invaluable reference for researchers and students.
  • Article
    Full-text available
    • Andrew B Smith
      Andrew B Smith
    • Andy Gale
      Andy Gale
    • Neale Monks
      Neale Monks
    The association between mass extinction in the marine realm and eustatic sea-level change in the Mesozoic is well documented, but perplexing, because it seems implausible that sea-level change could actually cause a major extinction, However, large-scale cycles of sea-level change can and do alter the ratio of shallow to deep marine continental-shelf deposits preserved in the rock record both regionally and globally. This taphonomic megabias alone could be driving patterns of first and last occurence and standing diversity because diversity and preservation potential both change predictably with water depth. We show that the Cenomanian/Turonian faunal event in western Europe has all the predicted signatures expected if taphonomic megabias was the cause. Grade taxa terminating in pseudoextinction and Lazarus taxa are predominantly found in the onshore facies that disappear for extended periods from the rock record. Before other mass extinctions are taken at face value, a much more careful analysis of biases in the rock record needs to be carried out, and faunal disappearances need to be analyzed within a phylogenetic framework.
  • Chapter
    Full-text available
    • Philip W. Signor
    • Jere H. Lipps
      Jere H. Lipps
    Catastrophic hypotheses for mass extinctions are commonly criticized because many taxa gradually disappear from the fossil record prior to the extinction. Presumably, a geologically instantaneous catastrophe would not cause a reduction in diversity or a series of minor extinctions before the actual mass extinction. Two types of sampling effects, however, could cause taxa to appear to decline before their actual biotic extinction. The first of these is reduced sample size provided in the sedimentary record and the second, which we examine in greater detail, is artificial range truncation. The fossil record is discontinuous in time and the recorded ranges of species or of higher taxa can only extend to their last known occurrence in the fossil record. If the distribution of last occurrences is random with respect to actual biotic extinction, then apparent extinctions will begin well before a mass extinction and will gradually increase in frequency until the mass extinction event, thus giving the appearance of a gradual extinction. Other factors, such as regressions, can exacerbate the bias toward gradual disappearance of taxa from the fossil record. Hence, gradual extinction patterns prior to a mass extinction do not necessarily eliminate catastrophic extinction hypotheses. The recorded ranges of fossils, especially of uncommon taxa or taxa in habitats not represented by a continuous record, may be inadequate to test either gradual or catastrophic hypotheses.
  • Article
    Full-text available
    • Steve C. Wang
      Steve C. Wang
    • Richard K. Bambach
      Richard K. Bambach
    • Andrew H Knoll
      Andrew H Knoll
    In post-Cambrian time, five events—the end-Ordovician, end-Frasnian in the Late De-vonian, end-Permian, end-Triassic, and end-Cretaceous—are commonly grouped as the ''big five'' global intervals of mass extinction. Plotted by magnitude, extinction intensities for all Phanerozoic substages show a continuous distribution, with the five traditionally recognized mass extinctions located in the upper tail. Plotted by time, however, proportional extinctions clearly divide the Phan-erozoic Eon into six stratigraphically coherent intervals of alternating high and low extinction in-tensity. These stratigraphic neighborhoods provide a temporal context for evaluating the intensity of extinction during the ''big five'' events. Compared with other stages and substages in the same neighborhood, only the end-Ordovician, end-Permian, and end-Cretaceous extinction intensities appear as outliers. Moreover, when origination and extinction are considered together, only these three of the ''big five'' events appear to have been generated exclusively by elevated extinction. Low origination contributed more than high extinction to the marked loss of diversity in the late Fras-nian and at the end of the Triassic. Therefore, whereas the ''big five'' events are clearly times when diversity suffered mass depletion, only those at the end of the Ordovician, Permian, and Cretaceous periods unequivocally qualify as globally distinct mass extinctions. Each of the three has a unique pattern of extinction, and the diversity dynamics of these events differ, as well, from the other two major diversity depletions. As mass depletions of diversity have no common effect, common cau-sation seems unlikely.
  • Book
    • Felix Gradstein
      Felix Gradstein
    • James Ogg
      James Ogg
    • A.G. Smith
    un extracto en pdf
  • Book
    • W. B. Harland
    • R. L. Armstrong
    • A. V. Cox
    • D. G. Smith
  • Article
    • Mike Foote
    Changes in genus diversity within higher taxa of marine animals on the temporal scale of a few million years are more strongly correlated with changes in extinction rate than with chang- es in origination rate during the Paleozoic. After the Paleozoic the relative roles of origination and extinction in diversity dynamics are reversed. Metazoa as well as individual higher taxa shift from one mode of diversity dynamics to the other. The magnitude of taxonomic rates, the relative var- iance of origination and extinction rates, and the presence or absence of a long-term secular in- crease in diversity all fail to account for the shift in importance of origination and extinction in diversity changes. Origination and extinction rates both tend to be diversity-dependent, but dif- ferent modes of diversity-dependence may contribute to the change in diversity dynamics from the Paleozoic to the post-Paleozoic. During the Paleozoic, there is a weak tendency for extinction rates to be more diversity-dependent than origination rates, whereas after the Paleozoic the two rates are about equally diversity-dependent on average.
  • Article
    • S. M. Holland
    In several increasingly realistic steps, a model of the stratigraphic distribution of fossils is presented. The first and simplest step assumes that if a taxon was extant it will have been preserved. The second step admits that if a taxon was extant, there is some probability less than one that it will have been preserved. The third step assumes facies-controlled taxa and parasequence-style cyclicity. The final model incorporates depositional sequences and indicates that first and last occurrences will cluster at sequence boundaries and at flooding surfaces in the transgressive systems tract. Comparison of the model to data from the Upper Ordovician suggests that the modeled features are present in the fossil record. -from Author
  • Article
    • Sean Richard Connolly
      Sean Richard Connolly
    • Arnold I. Miller
    The estimation and interpretation of temporal patterns in origination and extinction rates is a major goal of paleobiology. However, the possibility of coincident variation in the quality and completeness of the fossil record makes the identification of such patterns particularly difficult. Previously, Nichols and Pollock (1983) proposed that capture-mark-recapture (CMR) models be adapted to address this problem. These models can be used to estimate both sampling and turnover rates, reducing the risk of confounding the two quantities. Since that time, theoretical advances have made possible the application of these tools to a much broader range of problems. This paper reviews those advances likely to be of greatest relevance in paleobiological studies. They include (1) joint estimation of per-taxon origination and extinction rates, (2) modeling sampling or turnover rates as explicit functions of causal variables, (3) ranking of alternative models according to their fit to the data, and (4) estimation of parameter values using multiple models. These are illustrated by application to an Ordovician database of benthic marine genera from key higher taxa. Robustness of these methods to violation of assumptions likely to be suspect in paleobiological studies further suggests that these models can make an important contribution to the quantitative study of macroevolutionary dynamics.
  • Article
    • David M. Raup
    • P. A. Sabine
    • P. Ashmole
    • A. W. Wolfendale
    The dramatic increase in our knowledge of large-body impacts that have occurred in Earth's history has led to strong arguments for the plausibility of meteorite impact as a cause of extinction. Proof of causation is often hampered, however, by our inability to demonstrate the synchronism of specific impacts and extinctions. A central problem is range truncation: the last reported occurrences of fossil taxa generally underestimate the true times of extinction. Range truncation, because of gaps in sedimentation, lack of preservation, or lack of discovery, can make sudden extinctions appear gradual and gradual extinctions appear sudden. Also, stepwise extinction may appear as an artefact of range truncation. These effects are demonstrated by experiments performed on data from field collections of Cretaceous ammonities from Zumaya (Spain). The challenge for future research is to develop a new calculus for treating biostratigraphic data so that fossils can provide more accurate assessments of the timing of extinctions.
  • Article
    Full-text available
    • Michael Foote
    • James S. Crampton
    • Alan Beu
      Alan Beu
    • Bruce A. Marshall
    New Zealand has the most complete Cenozoic molluscan fossil record in the Southern Hemisphere. In order to understand the true marine faunal history of the region, it is necessary first to identify apparent biodiversity changes that result simply from variations in the quality of the fossil record. The present study uses a range of methods to quantify both long-term, secular changes and short-term patterns of variation in sampling probability for New Zealand Cenozoic shelf molluscs. Overall, about one-third of all once-living Cenozoic species have been sampled, and average per-stage sampling probabilities are between 20% and 50%. Increase in per-stage sampling probability through time reflects the increase in outcrop area and ease of fossil recovery from older to younger stages. Short-term patterns of variation apparently are related to second-order sequence stratigraphic controls of preservation potential. Once the effects of stage duration are eliminated, patterns of stage-to-stage sampling probability reflect enhanced preservation in mid-cycle positions and, perhaps to a lesser extent, secondary post-depositional loss of stratigraphic record above and below sequence boundaries. Although this result mirrors patterns observed in Europe, it is possible that enhanced preservation mid-cycle is relatively more important at active margins, such as New Zealand, whereas secondary loss of record at the sequence boundary is more important at passive margins. Finally, it is worth noting that different methods and data compilations yield rather consistent estimates of short-term variation in sampling probability, lending confidence to the methods and suggesting that the patterns identified are likely to reflect true underlying features of the New Zealand marine fossil record.
  • Article
    • Michael Foote
    Temporal patterns of origination and extinction are essential components of many paleontological studies, but it has been difficult to obtain accurate rate estimates because the observed record of first and last appearances is distorted by the incompleteness of the fossil record. Here I analyze observed first and last appearances of marine animal and microfossil genera in a way that explicitly takes incompleteness and its variation into consideration. This approach allows estimates of true rates of origination and extinction throughout the Phanerozoic. Substantial support is provided for the proposition that most rate peaks in the raw data are real in the sense that they do not arise as a consequence of temporal variability in the overall quality of the fossil record. Even though the existence of rate anomalies is supported, their timing is nevertheless open to question in many cases. If one assumes that rates of origination and extinction are constant through a given stratigraphic interval, then peaks in revised origination rates tend to be displaced backward and extinction peaks forward relative to the peaks in the raw data. If, however, one assumes a model of pulsed turnover, with true originations concentrated at lower interval boundaries and true extinctions concentrated at upper interval boundaries, the apparent timing of extinction peaks is largely reliable at face value. Thus, whereas rate anomalies may well be real, precisely when they occurred is a question that cannot be answered definitively without independent support for a model of smooth versus pulsed rate variation. The pattern of extinction, particularly the major events, is more faithfully represented in the fossil record than that of origination. There is a tendency for the major extinction events to occur during stages in which the quality of the record is relatively high and for recoveries from extinctions to occur when the record is less complete. These results imply that interpretations of origination and extinction history that depend only on the existence of rate anomalies are fairly robust, whereas interpretations of the timing of events and the temporal covariation between origination and extinction may require substantial revision.
  • Article
    • Leigh M. Van Valen
    The early part of an adaptive radiation is thought1 to show more taxonomic turnover than later stages. I show here that the effect on probability of extinction is one of exponential decrease, and that in the case of marine families this regular decline was interrupted by the great Permian extinction. A new exponential decrease followed, at a somewhat faster rate. The Cretaceous–Palaeogene extinction is the only other one detectably different from the scatter, and it had no apparent effect on extinction in the Cenozoic. These regularities support an interactive view of large-scale community evolution but do not uniquely determine the nature of the interaction.
  • Article
    • Arnold I. Miller
    • Mike Foote
    It has long been suspected that trends in global marine biodiversity calibrated for the Phanerozoic may be affected by sampling problems. However, this possibility has not been evaluated definitively, and raw diversity trends are generally accepted at face value in macroevolutionary investigations. Here, we analyze a global-scale sample of fossil occurrences that allows us to determine directly the effects of sample size on the calibration of what is generally thought to be among the most significant global biodiversity increases in the history of life: the Ordovician Radiation. Utilizing a composite database that includes trilobites, brachiopods, and three classes of molluscs, we conduct rarefaction analyses to demonstrate that the diversification trajectory for the Radiation was considerably different than suggested by raw diversity time-series. Our analyses suggest that a substantial portion of the increase recognized in raw diversity depictions for the last three Ordovician epochs (the Llandeilian, Caradocian, and Ashgillian) is a consequence of increased sample size of the preserved and catalogued fossil record. We also use biometric data for a global sample of Ordovician trilobites, along with methods of measuring morphological diversity that are not biased by sample size, to show that morphological diversification in this major clade had leveled off by the Llanvirnian. The discordance between raw diversity depictions and more robust taxonomic and morphological diversity metrics suggests that sampling effects may strongly influence our perception of biodiversity trends throughout the Phanerozoic.
  • Article
    • Michael Foote
    Short-term fluctuations in the diversification rate of Paleozoic marine animal genera are more strongly correlated with extinction-rate variation than with origination-rate variation. Diversity dynamics are strikingly different in the Mesozoic and Cenozoic, when variation in origination is more important than extinction. Data on the lithologic context of taxonomic occurrences in the Paleobiology Database are used to assess the substrate affinities of Paleozoic genera. The greater role of extinction-rate variation in the Paleozoic is found to characterize genera with an affinity for carbonate substrates but not those that prefer terrigenous clastic substrates. It is therefore plausible that the Paleozoic to post-Paleozoic shift in diversity dynamics is underlain in part by the secular decline in the relative areal extent of carbonate environments, and the concomitant decline in the relative diversity of carbonate- versus clastic-loving taxa.
  • Article
    Full-text available
    • Shanan E Peters
      Shanan E Peters
    Short-term variations in rates of taxonomic extinction and origination in the fossil record may be the result of true changes in rates of turnover, variable rates of fossil preservation, or some combination of the two. Here, positive extinction and origination rate excursions among Phaner-ozoic marine animal genera are reexpressed in terms of the amount of normal, background time they represent. In addition to providing a background-adjusted calibration of rate intensities, this reexpression determines the durations of sampling gaps that would be required to explain entirely all observed rate excursions as sampling artifacts. This possibility is explored by analyzing a new compilation of the timing and duration of sedimentary hiatuses in North America. Hiatuses spanning more than approximately one million years (Myr) in the marine sedimentary rock record have a mean duration of 73 Myr. There are two major hiatus types—those that form in response to long-duration tectonic cycles and that bound the major Sloss-scale sequences (mean duration 200 Myr), and those that form in response to shorter-duration changes in sediment ac-commodation space and that occur within major Sloss-scale sequences (mean duration less than 23 Myr). The latter are approximately exponentially distributed and have a mean duration that is comparable to the mean duration of intervening sedimentary rock packages. Although sedimentary hiatuses are generally long enough in duration to accommodate the hy-pothesis that short-term variations in rates of genus origination and extinction are artifacts of sam-pling failures at major unconformities (''Unconformity Bias'' hypothesis), the observed evolution-ary rates are not correlated with hiatus durations. Moreover, hiatuses that follow the major mass extinctions are not long in comparison to most other non–mass extinction intervals. These results do not support the hypothesis that hiatuses at major unconformities alone have artificially clustered genus first and last occurrences, thereby causing many of the documented statistical similarities between the temporal structure of the sedimentary rock record and macroevolutionary patterns. Instead, environmental changes related to the expansion and contraction of marine environments may have been the primary forcers of both biological turnover and the spatio-temporal pattern of sediment accumulation. Fully testing this ''Common Cause'' hypothesis requires quantifying and overcoming lingering taxonomic, biostratigraphic, facies, and numerous other biases that are both inherent in geologic data and imposed by imperfect knowledge of the fossil record.
  • Article
    • John Alroy
    This paper documents a series of methodological innovations that are relevant to mac-roevolutionary studies. The new methods are applied to updated faunal and body mass data sets for North American fossil mammals, documenting several key trends across the late Cretaceous and Cenozoic. The methods are (1) A maximum likelihood formulation of appearance event or-dination. The reformulated criterion involves generating a maximally likely hypothesized relative ordering of first and last appearances (i.e., an age range chart). The criterion takes faunal occur-rences, stratigraphic relationships, and the sampling probability of individual genera and species into account. (2) A nonparametric temporal interpolation method called ''shrink-wrapping'' that makes it possible to employ the greatest possible number of tie points without violating monoto-nicity or allowing abrupt changes in slopes. The new calibration method is used in computing pro-visional definitions of boundaries among North American land mammal ages. (3) Additional meth-ods for randomized subsampling of faunal lists, one weighting the number of lists that have been drawn by the sum of the square of the number of occurrences in each list, and one further modi-fying this approach to account for long-term changes in average local species richness. (4) Foote's new equations for instantaneous speciation and extinction rates. The equations are rederived and used to generate time series, confirm that logistic dynamics result from the diversity dependence of speciation but not extinction, and define the median duration of species (i.e., 2.6 m.y. for Eocene– Pleistocene mammals). (5) A method employing the G likelihood ratio statistic that is used to quan-tify the volatility of changes in the relative proportion of species falling in each of several major taxonomic groups. (6) Univariate measures of body mass distributions based on ordinary moment statistics (mean, standard deviation, skewness, kurtosis). These measures are favored over the method of cenogram analysis. Data are presented showing that even diverse individual fossil col-lections merely yield a noisy version of the same pattern seen in the overall continental data set. Peaks in speciation rates, extinction rates, proportional volatility, and shifts in body mass distri-butions occur at different times, suggesting that environmental perturbations do not have simple effects on the biota.
  • Article
    Full-text available
    • James S. Crampton
    • Michael Foote
    • Alan Beu
      Alan Beu
    • Gns
    In recent years several authors have questioned the reality of a widely accepted and ap-parently large increase in marine biodiversity through the Cenozoic. Here we use collection-level occurrence data from the rich and uniquely well documented New Zealand (NZ) shelfal marine mollusc fauna to test this question at a regional scale. Because the NZ data were generated by a small number of workers and have been databased over many decades, we have been able to either avoid or quantify many of the biases inherent in analyses of past biodiversity. In particular, our major conclusions are robust to several potential taphonomic and systematic biases and method-ological uncertainties, namely non-uniform loss of aragonitic faunas, biostratigraphic range errors, taxonomic errors, choice of time bins, choice of analytical protocols, and taxonomic rank of analysis. The number of taxa sampled increases through the Cenozoic. Once diversity estimates are stan-dardized for sampling biases, however, we see no evidence for an increase in marine mollusc di-versity in the NZ region through the middle and late Cenozoic. Instead, diversity has been ap-proximately constant for much of the past 40 Myr and, at the species and genus levels, has declined over the past 5 Myr. Assuming that the result for NZ shelfal molluscs is representative of other taxonomic groups and other temperate faunal provinces, then this suggests that the postulated global increase in diversity is either an artifact of sampling bias or analytical methods, resulted from increasing provinciality, or was driven by large increases in diversity in tropical regions. We see no evidence for a species-area effect on diversity. Likewise, we are unable to demonstrate a relationship between marine temperature and diversity, although this question should be re-ex-amined once refined shallow marine temperature estimates become available.
  • Chapter
    • B. J. Efron
    • Rob Tibshirani
      Rob Tibshirani
  • Article
    • John Alroy
    The coordinated stasis model has far-reaching implications. Among them are three important predictions concerning diversity dynamics that I test here against the Cenozoic fossil record of terrestrial North American mammals. First, origination and extinction rates should be correlated; second, turnover should be a composite function of very low background rates and occasional, dramatic turnover pulses; and finally, stasis should result from ecological (niche) incumbency, with the domains of incumbent species being defined by ecological similarity, which in the case of mammals corresponds closely with taxonomic affinity. The data used to test these hypotheses are standing diversity levels and counts of originations and extinctions for 1193 genera and 3161 species. Instead of relying on a traditional time scale comprised of “ages” having uneven and unpredictable durations, the diversity curve is computed directly from a multivariate ordination of 3870 faunal lists, and then sectioned into 1.0 m.y. intervals. The lists span the late Cretaceous through late Pleistocene interval, exclusive of the Wisconsinan, and are taxonomically standardized to remove junior synonyms, out-dated combinations, and nomina dubia. Because Cretaceous and Paleocene diversity dynamics are idiosyncratic, only the last 55 intervals (Eocene-Pleistocene: 55-0.01 Ma) are analyzed. The test of origination and extinction rates shows that an apparent correlation between them is a statistical artifact related to the necessary coincidence of first and last appearances for taxa known from just one interval. The test of variation in turnover shows that most of the observed extinction rates could be generated by a single, invariant underlying rate, wheras origination rates show many well-defined pulses. Furthermore, origination pulses within particular orders are not fully coincident. The very largest pulses of origination therefore seem to be mediated by key adaptations within particular groups, not by the general opportunity to fill niches opened up by extinction. Both of these tests argue against the idea of sweeping “reorganization” intervals bounding placid “stasis” intervals, and against Vrba's turnover pulse hypothesis. Finally, tests for niche incumbency, based on plots of per-taxon turnover rates against standing diversity, show that incumbency is widespread and mediated by the suppression of origination at high diversity levels in all groups. Extinction is a far less important controlling factor. Because orders are ecologically distinct, but random subsamples of the entire data set actually show stronger controls than groupings based on ordinal affinity, it appears that niche space has little or no important ecological substructuring. Therefore, mammalian diversity seems to be integrated at the highest possible taxonomic level, in opposition to the coordinated stasis concept of static guilds. On balance, the results indicate that although the data are robust and provide strong support for the niche incumbency model and the idea of diversity equilibrium, they generally disconfirm the unique predictions of coordinated stasis.
  • Article
    • Peter M. Sheehan
      Peter M. Sheehan
    Ecologic Evolutionary Units (EEUs) were long intervals of Phanerozoic time during which marine communities maintained stable ecologic structures. Boucot (1983) recognized 12 Ecologic Evolutionary Units and numbered them EEU I through EEU XII. The Ecologic Evolutionary Units are revised, and three are eliminated because they were intervals of community recovery following extinction events. Community structures were controlled by the composition of the Evolutionary Faunas of Sepkoski (1981), and communities became increasingly complex during each successive Evolutionary Fauna. To reflect their connections with the EFs the nine EEUs are renamed using a prefix designating the Evolutionary Fauna in which the EEUs occur. C1 and C2 are from the Cambrian EF, P1–4 are from the Paleozoic EF, and M1–3 are from the Modern EF.Within each Evolutionary Fauna communities in similar environmental setting in different EEUs have similar ecologic structures, and are recognized as congruent communities. Extinction events destroyed community organizations and removed evolutionary constraints, which allowed many species to move into new ecologic settings during the recovery intervals.
  • Article
    • Peter M. Sheehan
      Peter M. Sheehan
    • George McGhee
      George McGhee
    • David Bottjer
      David Bottjer
    • Mary L. Droser
      Mary L. Droser
    The past two decades have seen extensive analyses of the taxonomic severity of major biodiversity crises in geologic time. In contrast, we propose here an alternative analysis of the ecological severity of biodiversity crises. It is clear that the ecological impacts of the five Phanerozoic biodiversity crises were not all the same. Ranking the five Phanerozoic biodiversity crises by ecological severity reveals that the taxonomic and ecological severities of the events are decoupled. The most striking example of the decoupling is the end-Cretaceous biodiversity crisis, which is the least severe in terms of taxonomic diversity loss yet is ecologically the second most severe event in the entire Phanerozoic. A second striking example is the end-Ordovician biodiversity crisis: the environmental degradation produced by the end-Ordovician glaciations precipitated a major loss of marine diversity, yet the extinction failed to eliminate any key taxa or evolutionary traits, and was of minimal ecological impact.We suggest that the decoupled severities indicates that the ecological importance of component species in an ecosystem is at least as important as species diversity in maintaining the integrity of the ecosystem and that this ecological phenomenon operates on geological timescales. The selective elimination of dominant and/or keystone taxa that occurs in the ecologically most devastating biodiversity crises indicates that a strategy emphasizing the preservation of taxa with high ecological value is necessary to mitigate the ecological effects of the current ongoing loss of global biodiversity.
  • Chapter
    • Bradley Efron
    • Robert Tibshirani
      Robert Tibshirani
    Statistics is a subject of many uses and surprisingly few effective practitioners. The traditional road to statistical knowledge is blocked, for most, by a formidable wall of mathematics. The approach in An Introduction to the Bootstrap avoids that wall. It arms scientists and engineers, as well as statisticians, with the computational techniques they need to analyze and understand complicated data sets.
  • Article
    • David Jablonski
    Mass extinctions are important to macroevolution not only because they involve a sharp increase in extinction intensity over ''background'' levels, but also because they bring a change in extinction selectivity, and these quantitative and qualitative shifts set the stage for evolutionary recoveries. The set of extinction intensities for all stratigraphic stages appears to fall into a single right-skewed distribution, but this apparent continuity may derive from failure to factor out the well-known secular trend in background extinction: high early Paleozoic rates fill in the gap be- tween later background extinction and the major mass extinctions. In any case, the failure of many organism-, species-, and clade-level traits to predict survivorship during mass extinctions is a more important challenge to the extrapolationist premise that all macroevolutionary processes are sim- ply smooth extensions of microevolution. Although a variety of factors have been found to correlate with taxon survivorship for particular extinction events, the most pervasive effect involves geo- graphic range at the clade level, an emergent property independent of the range sizes of constituent species. Such differential extinction would impose ''nonconstructive selectivity,'' in which survi- vorship is unrelated to many organismic traits but is not strictly random. It also implies that cor- relations among taxon attributes may obscure causation, and even the focal level of selection, in the survival of a trait or clade, for example when widespread taxa within a major group tend to have particular body sizes, trophic habits, or metabolic rates. Survivorship patterns will also be sensitive to the inexact correlations of taxonomic, morphological, and functional diversity, to phylogeneti- cally nonrandom extinction, and to the topology of evolutionary trees. Evolutionary recoveries may be as important as the extinction events themselves in shaping the long-term trajectories of indi- vidual clades and permitting once-marginal groups to diversify, but we know little about sorting processes during recovery intervals. However, both empirical extrapolationism (where outcomes can be predicted from observation of pre- or post-extinction patterns) and theoretical extrapola- tionism (where mechanisms reside exclusively at the level of organisms within populations) evi- dently fail during mass extinctions and their evolutionary aftermath. This does not mean that con- ventional natural selection was inoperative during mass extinctions, but that many features that promoted survivorship during background times were superseded as predictive factors by higher- level attributes. Many intriguing issues remain, including the generality of survivorship rules across extinction events; the potential for gradational changes in selectivity patterns with extinction intensity or the volatility of target clades; the heritability of clade-level traits; the macroevolution- ary consequences of the inexact correlations between taxonomic, morphological, and functional diversity; the factors governing the dynamics and outcome of recoveries; and the spatial fabric of extinctions and recoveries. The detection of general survivorship rules—including the disappear- ance of many patterns evident during background times—demonstrates that studies of mass ex- tinctions and recovery can contribute substantially to evolutionary theory.
  • Article
    • Richard K. Bambach
      Richard K. Bambach
    Recent analyses of Sepkoski's genus-level compendium show that only three events form a statistically separate class of high extinction intensities when only post-Early Ordovician intervals are considered, but geologists have called numerous events mass extinctions. Is this a conflict? A review of different methods of tabulating data from the Sepkoski database reveals 18 intervals during the Phanerozoic have peaks of both magnitude and rate of extinction that appear in each tabulating scheme. These intervals all fit Sepkoski's definition of mass extinction. However, they vary widely in timing and effect of extinction, demonstrating that mass extinctions are not a homogeneous group of events. No consensus has been reached on the kill mechanism for any marine mass extinction. In fact, adequate data on timing in ecologic, rather than geologic, time and on geographic and environmental distribution of extinction have not yet been systematically compiled for any extinction event.
  • Article
    Full-text available
    • Andrew B Smith
      Andrew B Smith
    • Neale Monks
      Neale Monks
    The association between mass extinction in the marine realm and eustatic sea-level change in the Mesozoic is well documented, but perplexing, because it seems implausible that sea- level change could actually cause a major extinction. However, large-scale cycles of sea-level change can and do alter the ratio of shallow to deep marine continental-shelf deposits preserved in the rock record both regionally and globally. This taphonomic megabias alone could be driving pat- terns of first and last occurrence and standing diversity because diversity and preservation poten- tial both change predictably with water depth. We show that the Cenomanian/Turonian faunal event in western Europe has all the predicted signatures expected if taphonomic megabias was the cause. Grade taxa terminating in pseudoextinction and Lazarus taxa are predominantly found in the onshore facies that disappear for extended periods from the rock record. Before other mass extinctions are taken at face value, a much more careful analysis of biases in the rock record needs to be carried out, and faunal disappearances need to be analyzed within a phylogenetic framework.
  • Article
    • Michael Foote
    Apparent variation in rates of origination and extinction reflects the true temporal pattern of taxonomic rates as well as the distorting effects of incomplete and variable preservation, effects that are themselves exacerbated by true variation in taxonomic rates. Here I present an approach that can undo these distortions and thus permit estimates of true taxonomic rates, while providing estimates of preservation in the process. Standard survivorship probabilities are modified to incorporate variable taxonomic rates and rates of fossil recovery. Time series of these rates are explored by numerical optimization until the set of rates that best explains the observed data is found. If internal occurrences within stratigraphic ranges are available, or if temporal patterns of fossil recovery can otherwise be assumed, these constraints can be exploited, but they are by no means necessary. In its most general form, the approach requires no data other than first and last appearances. When tested against simulated data, the method is able to recover temporal patterns in rates of origination, extinction, and preservation. With empirical data, it yields estimates of preservation rate that agree with those obtained independently by tabulating internal occurrences within stratigraphic ranges. Moreover, when empirical occurrence data are artificially degraded, the method detects the resulting gaps in sampling and corrects taxonomic rates. Preliminary application to data on Paleozoic marine animals suggests that some features of the apparent record, such as the forward smearing of true origination events and the backward smearing of true extinction events, can be detected and corrected. Other features, such as the end-Ordovician extinction, may be fairly accurate at face value.
  • Article
    • Michael Foote
    The pattern of variation in taxonomic turnover on short timescales is expected to leave detectable signals even when taxonomic data are compiled at coarser timescales. Global, stage-level data on first and last appearances of marine animal genera are analyzed to determine whether it is more likely that origination and extinction were spread throughout stages or that they were con- centrated at a single episode per stage. The analysis takes incomplete and variable sampling of stratigraphic ranges into consideration, and it takes advantage of the fact that empirical sampling rates are within the range of values that allow the within-stage turnover models to be distinguished on the basis of stage-level data. The data strongly support the model of a single extinction pulse per stage over the alternative of continuous extinction within the stage. Pulsed origination is also supported over continuous origination, but the case is not as compelling as for extinction. Differ- ential support for pulsed turnover is not confined to a few stages. Pulsed turnover therefore ap- pears to be a general feature of the evolution of marine animals.
  • Article
    Full-text available
    • Steve C. Wang
      Steve C. Wang
    Do mass extinctions grade continuously into the background extinctions occurring throughout the history of life, or are they a fundamentally distinct phenomenon that cannot be explained by processes responsible for background extinction? Various criteria have been proposed for addressing this question, including approaches based on physical mechanisms, ecological se- lectivity, and statistical characterizations of extinction intensities. Here I propose a framework defining three types of continuity of mass and background extinc- tions—continuity of cause, continuity of effect, and continuity of magnitude. I test the third type of continuity with a statistical method based on kernel density estimation. Previous statistical ap- proaches typically have examined quantitative characteristics of mass extinctions (such as metrics of extinction intensity) and compared them with the distribution of such characteristics associated with background extinctions. If mass extinctions are outliers, or are separated by a gap from back- ground extinctions, the distinctness of mass extinctions is supported. In this paper I apply Silverman's Critical Bandwidth Test to test for the continuity of mass ex- tinctions by applying kernel density estimation and bootstrap modality testing. The method im- proves on existing work based on searching for gaps in histograms, in that it does not depend on arbitrary choices of parameters (such as bin widths for histograms), and provides a direct estimate of the significance of continuities or gaps in observed extinction intensities. I am thus able to test rigorously whether differences between mass extinctions and background extinctions are statisti- cally significant. I apply the methodology to Sepkoski's database of Phanerozoic marine genera. I conclude that mass and background extinctions appear to be continuous at this third level—continuity of mag- nitude—even though evidence suggests that they are discontinuous at the first and second levels.
  • Article
    • Steven M. Holland
    • Mark E. Patzkowsky
    With the exception of the Neogene, it is difficult in much of the fossil record to measure range offset; that is, the difference in age between the first or last occurrence of a species in a local section and its time of origination or extinction within the sedimentary basin. A coupled simulation that incorporates a model of sedimentary basin fill, a random-branching model of evolution, and a model of the ecological characteristics of species is used here to explore stratigraphic and ecologic controls on range offset. Median values of range offset in much of the fossil record are predicted to range from several hundred k.y. to a few m.y., for a wide variety of stratigraphic architectures and species ecologies. Higher than average values of range offset are favored by unconformities of long duration, rapid facies changes of large magnitude, persistent monotonic trends in facies change, increased facies specificity of species, and decreased species abundance. These model predictions can be used as a guide for interpreting field data on first and last occurrences, such as evaluating zones of likely high or low biostratigraphic precision. Similarly, these results can be used to evaluate the support for paleobiological interpretations of local radiations, migrations, and extinction episodes.
  • Article
    Full-text available
    • Norman Macleod
      Norman Macleod
    • Peter Rawson
      Peter Rawson
    • P. L. Forey
    • Jeremy R. Young
      Jeremy R. Young
    Mass extinctions are recognized through the study of fossil groups across event horizons, and from analyses of long-term trends in taxonomic richness and diversity. Both approaches have inherent flaws, and data that once seemed reliable can be readily superseded by the discovery of new fossils and/or the application of new analytical techniques. Herein the current state of the Cretaceous-Tertiary (K-T) biostratigraphical record is reviewed for most major fossil clades, including: calcareous nannoplankton, dinoflagellates, diatoms, radiolaria, foraminifera, ostracodes, scleractinian corals, bryozoans, brachio-pods, molluscs, echinoderms, fish, amphibians, reptiles and terrestrial plants (macrofossils and palynomorphs). These reviews take account of possible biasing factors in the fossil record in order to extract the most comprehensive picture of the K-T biotic crisis available. Results suggest that many faunal and floral groups (ostracodes, bryozoa, ammonite cephalopods, bivalves, archosaurs) were in decline throughout the latest Maastrichtian while others (diatoms, radiolaria, benthic foraminifera, brachiopods, gastropods, fish, amphibians, lepidosaurs, terrestrial plants) passed through the K-T event horizon with only minor taxonomic richness and/or diversity changes. A few microfossil groups (calcareous nannoplankton, dinoflagellates, planktonic foraminifera) did experience a turnover of varying magnitudes in the latest Maastrichtian-earliest Danian. However, many of these turnovers, along with changes in ecological dominance patterns among benthic foraminifera, began in the latest Maastrichtian. Improved taxonomic estimates of the overall pattern and magnitude of the K-T extinction event must await the development of more reliable systematic and phylogenetic data for all Upper Cretaceous clades.
  • Article
    • David M. Raup
    • J.J. Jr Sepkoski
    The temporal distribution of the major extinctions over the past 250 million years has been investigated statistically using various forms of time series analysis. The analyzed record is based on variation in extinction intensity for fossil families of marine vertebrates, invertebrates, and protozoans and contains 12 extinction events. The 12 events show a statistically significant periodicity (P less than 0.01) with a mean interval between events of 26 million years. Two of the events coincide with extinctions that have been previously linked to meteorite impacts (terminal Cretaceous and Late Eocene). Although the causes of the periodicity are unknown, it is possible that they are related to extraterrestrial forces (solar, solar system, or galactic).
  • Article
    Full-text available
    • Charles R. Marshall
    • Peter Ward
      Peter Ward
    Incompleteness of the fossil record has confounded attempts to establish the role of the end-Cretaceous bolide impact in the Late Cretaceous mass extinctions. Statistical analysis of latest Cretaceous outer-shelf macrofossils from western European Tethys reveals (i) a major extinction at or near the Cretaceous-Tertiary (K-T) boundary, probably caused by the impact, (ii) either a faunal abundance change or an extinction of up to nine ammonite species associated with a regression event shortly before the boundary, (iii) gradual extinction of most inoceramid bivalves well before the K-T boundary, and (iv) background extinction of approximately six ammonites throughout the latest Cretaceous.
  • Article
    Full-text available
    • James W. Kirchner
      James W. Kirchner
    • Anne Weil
    How quickly does biodiversity rebound after extinctions? Palaeobiologists have examined the temporal, taxonomic and geographic patterns of recovery following individual mass extinctions in detail, but have not analysed recoveries from extinctions throughout the fossil record as a whole. Here, we measure how fast biodiversity rebounds after extinctions in general, rather than after individual mass extinctions, by calculating the cross-correlation between extinction and origination rates across the entire Phanerozoic marine fossil record. Our results show that extinction rates are not significantly correlated with contemporaneous origination rates, but instead are correlated with origination rates roughly 10 million years later. This lagged correlation persists when we remove the 'Big Five' major mass extinctions, indicating that recovery times following mass extinctions and background extinctions are similar. Our results suggest that there are intrinsic limits to how quickly global biodiversity can recover after extinction events, regardless of their magnitude. They also imply that today's anthropogenic extinctions will diminish biodiversity for millions of years to come.
  • Article
    Full-text available
    • Andrew B Smith
      Andrew B Smith
    Patterns of origination, extinction and standing diversity through time have been inferred from tallies of taxa preserved in the fossil record. This approach assumes that sampling of the fossil record is effectively uniform over time. Although recent evidence suggests that our sampling of the available rock record has indeed been very thorough and effective, there is also overwhelming evidence that the rock record available for sampling is itself distorted by major systematic biases. Data on rock outcrop area compiled for post-Palaeozoic sediments from Western Europe at stage level are presented. These show a strongly cyclical pattern corresponding to first- and second-order sequence stratigraphical depositional cycles. Standing diversity increases over time and, at the coarsest scale, is decoupled from surface outcrop area. This increasing trend can therefore be considered a real pattern. Changes in standing diversity and origination rates over time-scales measured in tens of millions of years, however, are strongly correlated with surface outcrop area. Extinction peaks conform to a random-walk model, but larger peaks occur at just two positions with respect to second-order stratigraphical sequences, towards the culmination of stacked transgressive system tracts and close to system bases, precisely the positions where taxonomic last occurrences are predicted to cluster under a random distribution model. Many of the taxonomic patterns that have been described from the fossil record conform to a species-area effect. Whether this arises primarily from sampling bias, or from changing surface area of marine shelf seas through time and its effect on biodiversity, remains problematic.
  • Article
    Full-text available
    • Charles R. Marshall
    • J Alroy
    • Richard K. Bambach
    • A Webber
    Global diversity curves reflect more than just the number of taxa that have existed through time: they also mirror variation in the nature of the fossil record and the way the record is reported. These sampling effects are best quantified by assembling and analyzing large numbers of locality-specific biotic inventories. Here, we introduce a new database of this kind for the Phanerozoic fossil record of marine invertebrates. We apply four substantially distinct analytical methods that estimate taxonomic diversity by quantifying and correcting for variation through time in the number and nature of inventories. Variation introduced by the use of two dramatically different counting protocols also is explored. We present sampling-standardized diversity estimates for two long intervals that sum to 300 Myr (Middle Ordovician-Carboniferous; Late Jurassic-Paleogene). Our new curves differ considerably from traditional, synoptic curves. For example, some of them imply unexpectedly low late Cretaceous and early Tertiary diversity levels. However, such factors as the current emphasis in the database on North America and Europe still obscure our view of the global history of marine biodiversity. These limitations will be addressed as the database and methods are refined.
  • Article
    • Mike Foote
    • JR. J. J. Sepkoski
    Measuring the completeness of the fossil record is essential to understanding evolution over long timescales, particularly when comparing evolutionary patterns among biological groups with different preservational properties. Completeness measures have been presented for various groups based on gaps in the stratigraphic ranges of fossil taxa and on hypothetical lineages implied by estimated evolutionary trees. Here we present and compare quantitative, widely applicable absolute measures of completeness at two taxonomic levels for a broader sample of higher taxa of marine animals than has previously been available. We provide an estimate of the probability of genus preservation per stratigraphic interval, and determine the proportion of living families with some fossil record. The two completeness measures use very different data and calculations. The probability of genus preservation depends almost entirely on the Palaeozoic and Mesozoic records, whereas the proportion of living families with a fossil record is influenced largely by Cenozoic data. These measurements are nonetheless highly correlated, with outliers quite explicable, and we find that completeness is rather high for many animal groups.
  • Article
    • Mike Foote
    • A.I. Miller
    It has long been suspected that trends in global marine biodiversity calibrated for the Phanerozoic may be affected by sampling problems. However, this possibility has not been evaluated definitively, and raw diversity trends are generally accepted at face value in macroevolutionary investigations. Here, we analyze a global-scale sample of fossil occurrences that allows us to determine directly the effects of sample size on the calibration of what is generally thought to be among the most significant global biodiversity increases in the history of life: the Ordovician Radiation. Utilizing a composite database that includes trilobites, brachiopods, and three classes of molluscs, we conduct rarefaction analyses to demonstrate that the diversification trajectory for the Radiation was considerably different than suggested by raw diversity time-series. Our analyses suggest that a substantial portion of the increase recognized in raw diversity depictions for the last three Ordovician epochs (the Llandeilian, Caradocian, and Ashgillian) is a consequence of increased sample size of the preserved and catalogued fossil record. We also use biometric data for a global sample of Ordovician trilobites, along with methods of measuring morphological diversity that are not biased by sample size, to show that morphological diversification in this major clade had leveled off by the Llanvirnian. The discordance between raw diversity depictions and more robust taxonomic and morphological diversity metrics suggests that sampling effects may strongly influence our perception of biodiversity trends throughout the Phanerozoic.