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Understanding spatial variation in origination and extinction can help to unravel the mechanisms underlying macroevolutionary patterns. Although methods have been developed for estimating global origination and extinction rates from the fossil record, no framework exists for applying these methods to restricted spatial regions. Here, we test the efficacy of three metrics for regional analysis, using simulated fossil occurrences. These metrics are then applied to the marine invertebrate record of the Permian and Triassic to examine variation in extinction and origination rates across latitudes. Extinction and origination rates were generally uniform across latitudes for these time intervals, including during the Capitanian and Permian–Triassic mass extinctions. The small magnitude of this variation, combined with the possibility of its attribution to sampling bias, cautions against linking any observed differences to contrasting evolutionary dynamics. Our results indicate that origination and extinction levels were more variable across clades than across latitudes.

Biotic interactions and community structure are seldom examined in mass extinction studies but must be considered if we are to truly understand extinction and recovery dynamics at the ecosystem scale. Here, we model shallow marine food web structure across the Toarcian extinction event in the Cleveland Basin, UK using a trait-based inferential modelling framework. First, we subjected our pre-extinction community to extinction cascade simulations in order to identify the nature of extinction selectivity and dynamics. Second, we tracked the pattern and duration of the recovery of ecosystem structure and function following the extinction event. In agreement with postulated scenarios, we found that primary extinctions targeted towards infaunal and epifaunal benthic guilds reproduced the empirical post-extinction community. These results are consistent with geochemical and lithological evidence of an anoxia/dysoxia kill mechanism for this extinction event. Structural and functional metrics show that the extinction event caused a switch from a diverse, stable community with high levels of functional redundancy to a less diverse, more densely connected, and less stable community of generalists. Ecological recovery appears to have lagged behind the recovery of biodiversity, with most metrics only beginning to return to pre-extinction levels ∼7 million years after the extinction event. This protracted pattern supports the theory of delayed benthic ecosystem recovery following mass extinctions even in the face of seemingly recovering taxonomic diversity.

The latitudinal diversity gradient (LDG) is recognized as one of the most pervasive, global patterns of present-day biodiversity. However, the controlling mechanisms have proved difficult to identify because many potential drivers covary in space. The geological record presents a unique opportunity for understanding the mechanisms which drive the LDG by providing a direct window to deep-time biogeographic dynamics. Here we used a comprehensive database containing 52,318 occurrences of marine fossils to show that the shape of the LDG changed greatly during the Permian-Triassic mass extinction from showing a significant tropical peak to a flattened LDG. The flat LDG lasted for the entire Early Triassic (∼5 My) before reverting to a modern-like shape in the Middle Triassic. The environmental extremes that prevailed globally, especially the dramatic warming, likely induced selective extinction in low latitudes and accumulation of diversity in high latitudes through origination and poleward migration, which combined together account for the flat LDG of the Early Triassic.

The climatic and environmental impact of exclusively volcanic CO2 emissions is assessed during the main effusive phase of the Central Atlantic Magmatic Province (CAMP), which is synchronous with the end-Triassic mass extinction. CAMP volcanism occurred in brief and intense eruptive pulses each producing extensive basaltic lava flows. Here, CAMP volcanic CO2 injections into the surface system are modelled using a biogeochemical box model for the carbon cycle. Our modelling shows that, even if positive feedback phenomena may be invoked to explain the carbon isotope excursions preserved in end-Triassic sedimentary records, intense and pulsed volcanic activity alone may have caused repeated temperature increases and pH drops, up to 5 °C and about 0.2 log units respectively. Hence, rapid and massive volcanic CO2 emissions from CAMP, on a similar scale to current anthropogenic emissions, severely impacted on climate and environment at a global scale, leading to catastrophic biotic consequences.

Anthropogenic activity is changing Earth's climate and ecosystems in ways that are potentially dangerous and disruptive to humans. Greenhouse gas concentrations in the atmosphere continue to rise, ensuring that these changes will be felt for centuries beyond 2100, the current benchmark for projection. Estimating the effects of past, current, and potential future emissions to only 2100 is therefore short-sighted. Critical problems for food production and climate-forced human migration are projected to arise well before 2100, raising questions regarding the habitability of some regions of the Earth after the turn of the century. To highlight the need for more distant horizon scanning, we model climate change to 2500 under a suite of emission scenarios and quantify associated projections of crop viability and heat stress. Together, our projections show global climate impacts increase significantly after 2100 without rapid mitigation. As a result, we argue that projections of climate and its effects on human well-being and associated governance and policy must be framed beyond 2100., Global Change Biology, 28 (2), ISSN:1354-1013, ISSN:1365-2486

Reconstructing ancient community assemblages and the ecological relationships between extinct organisms is a major challenge due to the shortcomings of the fossil record. The uncertainty surrounding the life habits of extinct organisms has proven to be a major hurdle for our understanding of the evolution of ecosystem structure through time. One such period of interest is the Mesozoic Marine Revolution (MMR), where escalation is proposed to have driven major changes in marine food webs which led to the establishment of modern marine ecosystem structure. The timing of the MMR is heavily debated, with proposals ranging from an Early Triassic to a Cretaceous/Cenozoic origin. We present a meta-community analysis of the Peterborough Member (Callovian, UK) with the aim of constraining the timing of the MMR. We assigned traits (i.e. body size, feeding mode, motility, tiering) that define interactions in modern systems to all fossil organisms and used rules based on foraging behaviour to model meta-community food web structure. We then compare the modelled Peterborough Member food webs with those of well-constrained modern marine ecosystems to shed light on whether modern marine ecosystem was established by the end of the Middle Jurassic.

The role of ocean anoxia as a cause of the end-Triassic marine mass extinction is widely debated. Here, we present carbonate-associated sulfate δ34S data from sections spanning the Late Triassic–Early Jurassic transition, which document synchronous large positive excursions on a global scale occurring in ~50 thousand years. Biogeochemical modeling demonstrates that this S isotope perturbation is best explained by a fivefold increase in global pyrite burial, consistent with large-scale development of marine anoxia on the Panthalassa margin and northwest European shelf. This pyrite burial event coincides with the loss of Triassic taxa seen in the studied sections. Modeling results also indicate that the pre-event ocean sulfate concentration was low (

The decline in species richness from the equator to the poles is referred to as the latitudinal diversity gradient (LDG). Higher equatorial diversity has been recognized for over 200 years, but the consistency of this pattern in deep time remains uncertain. Examination of spatial biodiversity patterns in the past across different global climate regimes and continental configurations can reveal how LDGs have varied over Earth history and potentially differentiate between suggested causal mechanisms. The Late Permian–Middle Triassic represents an ideal time interval for study, because it is characterized by large-scale volcanic episodes, extreme greenhouse temperatures and the most severe mass extinction event in Earth history. We examined terrestrial and marine tetrapod spatial biodiversity patterns using a database of global tetrapod occurrences. Terrestrial tetrapods exhibit a bimodal richness distribution throughout the Late Permian–Middle Triassic, with peaks in the northern low latitudes and southern mid-latitudes around 20–40° N and 60° S, respectively. Marine reptile fossils are known almost exclusively from the Northern Hemisphere in the Early and Middle Triassic, with highest diversity around 20° N. Reconstructed terrestrial LDGs contrast strongly with the generally unimodal gradients of today, potentially reflecting high global temperatures and prevailing Pangaean super-monsoonal climate system during the Permo-Triassic.

The coincidence between mass extinction events and the emplacement of Large Igneous Provinces (LIPs) in the Phanerozoic geological record points to the magmatic CO2 degassing as the potential trigger of rapid global-scale climatic and environmental changes. The Central Atlantic Magmatic Province (CAMP) is one of the Earth’s hugest LIPs, and is coincident with the end-Triassic extinction, at ca. 201.5 Ma. Such LIPs emplacement and associated magmatic CO2 degassing have traditionally been interpreted as occurring over periods much longer than those of anthropogenic CO2 emissions, however our improving understanding of LIPs activity is reducing these timescales, with the latest estimates indicating CAMP magmatic pulses lasting approximately a few centuries each and characterized by high eruption rates [1; 2]. We employed a biogeochemical model to investigate the effects on ocean-atmosphere system and climate of these CAMP magmatic pulses, and to test whether such rapid and intense magmatic CO2 degassing is consistent with the climatic, geochemical and palaeontological record of the end-Triassic. Hence, we compared the modern anthropogenic emissions (since the Industrial Revolution) with the pulsed magmatic degassing during CAMP emplacement, in order to evaluate the impact of rapid and intense events on climate and environment changes. [1] Knight et al. (2004), Earth Planet. Sci. Lett. 228, 143-160. [2] Marzoli et al. (2019), J. Petrol. 60, 945-996.

The Toarcian Oceanic Anoxic Event and associated early Toarcian mass extinction event (ETME) have attracted a great deal of research effort, focusing primarily on the causal mechanisms. In contrast, there is less known of the patterns of biotic recovery following this mass extinction (and others). Yet such recoveries are of interest as they record how surviving organisms radiate into newly vacated ecospace. The Cleveland Basin, North Yorkshire, has one of the most expanded Toarcian rock sections globally. Previous studies have presented a limited view of the recovery interval as the upper Toarcian sequence across much of the basin was truncated by a period of erosion during the Middle Jurassic. However, the Ravenscar coastal section preserves all of the upper Toarcian stratigraphy. In the summers of 2013 and 2017 JWA and CTSL collected 24,002 macrofossil specimens from 37 sample points covering 45 metres of the Ravenscar section, from the top of the Alum Shale Member of the Whitby Mudstone Formation to the top of the Blea Wyke Sandstone Formation. The samples included benthic taxa (principally bivalves and gastropods, with smaller number of brachiopods, echinoderms, serpulids, scaphopods, crustaceans and bryozoans) and nektic taxa (belemnites and ammonites). These allowed us to construct new range data, and allowed us a full evaluation of the biotic recovery from the ETME. Ecological tiering was the first to respond to the amelioration of conditions in the Bifrons Zone, approximately 1.75-2.71 million years following the extinction event. Many of the ecological groups that disappeared across the extinction interval began to reappear, although often represented by only a single species. Benthic species richness and ecological diversity subsequently dropped in the Variabilis and Thoarsense Zones, and then both increased substantially in the Levesquei Zone, coincident with the onset of sandy facies deposition in the basin, 5.1-6.89 million years after the extinction event. It was only then that species and ecological diversity regained their pre-extinction late Pliensbachian to Tenuicostatum Zone values. This surprisingly protracted recovery interval may have been caused by persistent environmental stress and/or sea-level change. Some of the benthic taxa appearing in the late Toarcian Levesquei Zone into the Cleveland Basin are typical of Middle Jurassic faunas. Future work will be to ascertain from where these immigrants came. This will present taxonomic challenges that require whole-community collaboration.

Variation in preservation and sampling probability clouds our estimates of past biodiversity. The most extreme examples are Lagerstätten faunas and floras. Although such deposits provide a wealth of information and represent true richness better than other deposits, they can create misleading diversity peaks because of their species richness. Here, we investigate how Lagerst€atten formations add to time series of vertebrate richness in the UK, Germany and China. The first two nations are associated with well-studied fossil records and the last is a country where palaeontology has a much shorter history; all three nations include noted Lagerstätten in their fossil records. Lagerstätten provide a larger proportion of China’s sampled richness than in Germany or the UK, despite comprising a smaller proportion of its fossiliferous deposits. The proportions of taxa that are unique to Lagerstätten vary through time and between countries. Further, in all regions, we find little overlap between the taxa occurring in Lagerstätten and in ‘ordinary’ formations within the same time bin, indicating that Lagerstätten preserve unusual faunas. As expected, fragile taxa make up a greater proportion of richness in Lagerstätten than the remainder of the fossil record. Surprisingly, we find that Lagerstätten account for a minority of peaks in the palaeodiversity curves of all vertebrates (18% in the UK; 36% in Germany and China), and Lagerst€atten count is gen- erally not a good overall predictor of the palaeodiversity sig- nal. Vastly different sampling probabilities through taxa, locations and time require serious consideration when analysing palaeodiversity curves.

The quality of the fossil record is essential for interpreting the significance of macroevolutionary patterns. Palaeodiversity is filtered through geological and human processes, and efforts to correct for these biases are part of a debate concerning the role of sampling proxies and standardisation in models of biodiversity. Here, we analyse the fossil record of mosasaurs in terms of fossil completeness as a measure of fossil quality, using three novel metrics of fossil completeness for a compilation of 4,083 specimens. All metrics correlate with each other. A new qualitative measure of character completeness (QCM), correlates with the phylogenetic character completeness metric. Mean completeness by species decreases with specimen count, and average completeness by substage varies significantly. Mean specimen completeness is higher for species-named fossils than those identified to genus and family. The effect of tooth-only specimens is analysed. Importantly, we find that completeness of species does not correlate with completeness of specimens. Completeness varies by palaeogeography, North American specimens showing higher completeness than those from Eurasia and Gondwana. These metrics can be used to identify exceptional preservation, with specimen completeness varying significantly by both formation and lithology. The Belgian Ciply Formation displays the highest completeness, and clay lithologies show higher completeness values than others. Neither species diversity nor sea level correlates significantly with fossil completeness. A GLS analysis using multiple variables agrees with this result. However, GLS shows that two variables have significant predictive value for modelling averaged diversity, namely sea level and mosasaur- and plesiosaur-bearing formations, the latter of which is shown to be redundant with diversity. Mosasaur completeness is not driven by sea level, nor is completeness limiting the diversity signal in the mosasaur record.

The Late Triassic and Early Toarcian extinction events are both associated with greenhouse warming events triggered by massive volcanism. These Mesozoic hyperthermals were responsible for the mass extinction of marine organisms and resulted in significant ecological upheaval. It has, however, been suggested that these events merely involved intensification of background extinction rates rather than significant shifts in the macroevolutionary regime and extinction selectivity. Here, we apply a multivariate modelling approach to a vast global database of marine organisms to test whether extinction selectivity varied through the Late Triassic and Early Jurassic. We show that these hyperthermals do represent shifts in the macroevolutionary regime and record different extinction selectivity compared to background intervals of the Late Triassic and Early Jurassic. The Late Triassic mass extinction represents a more profound change in selectivity than the Early Toarcian extinction but both events show a common pattern of selecting against pelagic predators and benthic photosymbiotic and suspension-feeding organisms, suggesting that these groups of organisms may be particularly vulnerable during episodes of global warming. In particular, the Late Triassic extinction represents a macroevolutionary regime change that is characterized by (i) the change in extinction selectivity between Triassic background intervals and the extinction event itself; and (ii) the differences in extinction selectivity between the Late Triassic and Early Jurassic as a whole.

After the enormous Permian-Triassic mass extinction, marine animals high in the food chain recovered the most quickly., The Permian-Triassic mass extinction was the worst crisis faced by life; it killed >90% of marine species in less than 0.1 million years (Ma). However, knowledge of its macroecological impact over prolonged time scales is limited. We show that marine ecosystems dominated by non-motile animals shifted to ones dominated by nektonic groups after the extinction. In Triassic oceans, animals at high trophic levels recovered faster than those at lower levels. The top-down rebuilding of marine ecosystems was still underway in the latest Triassic, ~50 Ma after the extinction, and contrasts with the ~5-Ma recovery required for taxonomic diversity. The decoupling between taxonomic and ecological recoveries suggests that a process of vacant niche filling before reaching the maximum environmental carrying capacity is independent of ecosystem structure building.

Taphonomic, geological and sampling processes have been cited as biasing richness measurements in the fossil record, and sampling proxies have been widely used to assess this. However, the link between sampling and taxonomic richness is poorly understood, and there has been much debate on the equivalence and relevance of proxies. We approach this question by combining both historical and novel data: a historical fossil occurrence dataset with uniquely high spatial resolution from the Upper Cretaceous Chalk Group of Hampshire, UK, and a newly compiled 3D geological model that maps subsurface extent. The geological model provides rock volumes, and these are compared with exposure and outcrop area, sampling proxies that have often been conflated in previous studies. The extent to which exposure area (true rock availability) has changed over research time is also tested. We find a trend of low Cenomanian to high Turonian to Campanian raw richness, which correlates with, and is possibly driven by, the number of specimens found. After sampling standardization, an unexpected mid-Turonian peak diversity is recovered, and sampling-standardized genus richness is best predicted by rock volume, suggesting a species–area (or ‘genus–area’) effect. Additionally, total exposure area has changed over time, but relative exposure remains the same. Supplementary materials : A locality list, abundance matrix and all correlation and modelling results are available at https://doi.org/10.6084/m9.figshare.c.3592208.

Many studies have highlighted correlations between palaeodiversity and sampling proxies. These correlations have been interpreted as evidence for bias, common cause, or redundancy between signals. Here, we compare a number of sampling proxies representing sedimentary rock volume, rock accessibility and worker effort with palaeodiversity through the predominantly terrestrial Triassic System in England and Wales. We find that proxies for sedimentary rock volume and accessibility do not correlate with palaeodiversity until the removal of facies-related preservational and palaeoecological factors. This indicates that a weak sampling signal may be present, but the effects of changing palaeoenvironments are far more important at the regional scale. Significant correlations between worker effort and palaeodiversity are detected, although this is likely to be a result of the preferential sampling of formations already known to be rich in fossils. The fact that there is little evidence for sedimentary rock bias in the fossil record of the Triassic of England and Wales suggests that either (1) sampling bias is not a major source of error at the regional scale or (2) sampling proxies are inadequate representations of geological and human sampling bias. Supplementary material: Correlation test results and raw time series data from the study are available at www.geolsoc.org.uk/SUP18567.

The first half of tetrapod evolution witnessed substantial diversification of the clade and several major turnovers and mass extinctions. In the time since their origin, more than 380 Myr ago, to the beginning of the Middle Jurassic 175 Myr ago, tetrapods apparently diversified fitfully, reaching their highest level in the Middle Permian, and showing major diversity declines in the late Moscovian, Early Permian, Wordian, lower Wuchiapingian, end-Permian, lower Anisian, lower Ladinian, Late Triassic (lower Norian to upper Rhaetian), end-Triassic, and Early Jurassic (upper Sinemurian, lower Pliensbachian). Of these diversity drops, only the end-Permian and end-Triassic correspond to recognised mass extinctions, and the late Moscovian and early Norian drops to other previously identified environmental crises. The remainder could be real extinction or turnover events, or partially artefacts of biased sampling. There are strong correlations between formation counts and tetrapod palaeodiversity, suggesting a sampling component in the raw data, but the covariation is not uniform through the whole time span, being poor from Devonian to Middle Permian, and better from Late Permian to Early Jurassic. There is limited evidence for covariation between the tetrapod palaeodiversity time series and other putative sampling metrics, such as specimen completeness, numbers of publications, map areas, gap-bounded sedimentary units, rock volumes, formations, and fossil collections. Modelling by multiple correlations shows that formation count is generally the best explanatory model, either on its own, or combined with other ‘sampling’ time series. However, it is not clear that formation count is independent of the palaeodiversity time series, because rises and falls in both signals could reflect variations in original diversity or in preservation or in sampling.

Most studies of the adequacy of the fossil record have been carried out at a global or continental scale, and they have used sampling proxies that generally do not incorporate all aspects of sampling (i.e. rock volume, accessibility, effort). Nonetheless, such studies have identified positive correlations between apparent diversity and various sampling proxies. The covariation of fossil and rock record signals has been interpreted as evidence for bias or for a common cause, such as sea level change, or as evidence that the signals are in some ways redundant with each other. Here, we compare a number of proxies representing the three main aspects of sampling, (1) sedimentary rock volume, (2) rock accessibility and (3) worker effort, with palaeodiversity in a geographically and stratigraphically constrained data set, the marine Lower Jurassic outcrop of the Dorset and East Devon Coast. We find that the proxies for rock volume and accessibility do not correlate well with the other sampling proxies, nor with apparent diversity, suggesting that the total amount of sedimentary rock preserved does not influence apparent diversity at a local scale, that is, the rock record at outcrop has been sampled efficiently. However, we do find some correlations between apparent diversity and proxies for worker effort. The fact that the proxies do not correlate significantly with each other suggests that none can be regarded as an all-encompassing sampling proxy that covers all aspects of bias. Further, the presence of some correlations between sampling proxies and diversity most probably indicates the bonanza effect, as palaeontologists have preferentially sampled the richest rock units.

Fossil specimens can be recovered easily only from exposed localities, so rock exposure area should represent a better proxy for rock availability than the frequently used outcrop (i.e., map) area. Data collected via remote sensing and GIS show that map area does not consistently correlate with exposure area in different regions. Proportional rock exposure is not geographically consistent and is influenced by a number of variables that are independent of outcrop area, including proximity to the coast, elevation, bedrock age, land use and lithology. These variables appear to be non-independent in their influence on rock exposure, and are not consistent in their effects across continents. The inconsistency in the correlation between outcrop and exposure area, and the variability in the influence of different factors on rock exposure, suggests that using outcrop area as a sampling proxy is poorly supported. The weaknesses in using outcrop area as a sampling proxy, highlighted by the lack of correlation with exposure area, suggest that a single accurate global sampling proxy may never be attained and it is premature to assume that paleodiversity curves can be corrected using such proxies. It is therefore preferable to work on a regional scale, comparing regional fossil collection data with a number of proxies representing all aspects of sampling. The lack of correlation between outcrop and exposure area suggests that the covariance detected between outcrop area and paleodiversity might be better explained by a common-cause model, and that geological megabiases may not have had as profound an effect on paleodiversity curves as previously thought.

Rock outcrop area and number of sedimentary formations have been widely used as sampling proxies in paleodiversity studies and have often been found to correlate with apparent paleodiversity. However, rock exposure area is a better proxy for the amount of sedimentary rock available for study than the widely used measures of outcrop area (i.e., map area) or number of formations. With the use of remote sensing and a geographic information system (GIS), it is possible to quantify rock exposure area accurately on a regional scale. Rock exposure area does not correlate well with either outcrop area or number of sedimentary formations, and the proportion of rock exposed in different areas can vary considerably with proximity to the coast, bedrock age, lithology, land use, and elevation. Therefore, this suggests that the correlation of paleodiversity and rock volume estimates is best explained by a common-cause hypothesis, rather than a geologic sampling bias hypothesis. GIS methods offer an efficient and accurate method of quantifying regional sedimentary rock exposure and may provide a helpful approach to assessing rock record bias on patterns in the fossil record.

Assessing the quality of the fossil record is notoriously hard, and many recent attempts have used sampling proxies that can be questioned. For example, counts of geological formations and estimated outcrop areas might not be defensible as reliable sampling proxies: geological formations are units of enormously variable dimensions that depend on rock heterogeneity and fossil content (and so are not independent of the fossil record), and outcrop areas are not always proportional to rock exposure, probably a closer indicator of rock availability. It is shown that in many cases formation counts will always correlate with fossil counts, whatever the degree of sampling. It is not clear, in any case, that these proxies provide a good estimate of what is missing in the gap between the known fossil record and reality; rather they largely explore the gap between known and potential fossil records. Further, using simple, single numerical metrics to correct global-scale raw data, or to model sampling-driven patterns may be premature. There are perhaps four approaches to exploring the incompleteness of the fossil record, (1) regionalscale studies of geological completeness; (2) regionalor clade-scale studies of sampling completeness using comprehensive measures of sampling, such as numbers of localities or specimens or fossil quality; (3) phylogenetic and gap-counting methods; and (4) model-based approaches that compare sampling as one of several explanatory variables with measures of environmental change, singly and in combination. We suggest that palaeontologists, like other scientists, should accept that their data are patchy and incomplete, and use appropriate methods to deal with this issue in each analysis. All that matters is whether the data are adequate for a designated study or not. A single answer to the question of whether the fossil record is driven by macroevolution or megabias is unlikely ever to emerge because of temporal, geographical, and taxonomic variance in the data. The fossil record is far from perfect, and palaeontologists must be concerned about inadequacy and bias (Raup 1972; Benton 1998; Smith 2001, 2007a). Fundamental issues concerning the quality and completeness of the fossil record were enunciated clearly by Charles Darwin (1859, pp. 287–288), who wrote: That our palaeontological collections are very imperfect, is admitted by every one. The remark of that admirable palaeontologist, the late Edward Forbes, should not be forgotten, namely, that numbers of our fossil species are known and named from single and often broken specimens, or from a few specimens collected on some one spot. Only a small portion of the surface of the earth has been geologically explored, and no part with sufficient care, as the important discoveries made every year in Europe prove. No organism wholly soft can be preserved. Shells and bones will decay and disappear when left on the bottom of the sea, where sediment is not accumulating. . . With respect to the terrestrial productions which lived during the Secondary and Palaeozoic periods, it is superfluous to state that our evidence from fossil remains is fragmentary in an extreme degree. Raup (1972) clarified the situation when he compared the ‘empirical’ model of Valentine (1969), a literal reading of the fossil record, with his ‘bias simulation model’ that explained the bulk of the apparent low diversity levels of marine invertebrates in the Palaeozoic as a sampling error. Two opposite viewpoints have been argued, either that the fossil record is good enough (e.g. Sepkoski et al. 1981; Benton 1995; Benton et al. 2000; Stanley 2007) or not good enough (e.g. Raup 1972; Alroy et al. 2001, 2008; Peters & Foote 2002; Alroy 2010) to show the main patterns of global diversification through time. A resolution between these opposite viewpoints does not appear close (Benton 2009; Erwin 2009; Marshall 2010). From: McGowan, A. J. & Smith, A. B. (eds) Comparing the Geological and Fossil Records: Implications for Biodiversity Studies. Geological Society, London, Special Publications, 358, 63–94. DOI: 10.1144/SP358.6 0305-8719/11/$15.00 # The Geological Society of London 2011. Key objective evidence for bias in the fossil record could be the extraordinary and ubiquitous correlation of sampling proxies and diversity curves: why is there such close tracking of measures of rock volume by palaeodiversity? There are three possible explanations: (1) rock volume/sampling drives the diversity signal (Peters & Foote 2001, 2002; Smith 2001, 2007a; Butler et al. 2011); (2) both signals reflect a third, or ‘common’, cause such as sea-level fluctuation (Peters 2005; Peters & Heim 2010); or (3) both signals are entirely or partially redundant (1⁄4 identical) with each other. In reality, the close correlation probably reflects a combination of all three factors in different proportions in any test case, and so it is probably fruitless to prolong the debate about which of the three models is correct, and which incorrect. Much of the literature on the quality of the rock and fossil records has focused on marine settings. This reflects the interests of palaeontologists who engage with these questions, and the fact that many marine rock records are more complete than most terrestrial (continental) rock records. However, the terrestrial fossil record is worth considering for several reasons: terrestrial life today is much more diverse than marine life, perhaps representing 85% of modern biodiversity (May 1990; Vermeij & Grosberg 2010), terrestrial life includes many major taxa that are sensitive to atmospheric, temperature, and topographic change and so are key indicator species in studies of global change, and for many terrestrial groups (e.g. angiosperms, insects, vertebrates) there are mature morphological and molecular phylogenies that enable cross-comparison between stratigraphic and cladistic data. In this paper, we explore the use of sampling proxies, and suggest that some commonly used measures, notably formation counts and outcrop areas, may not be useful or accurate measures of sampling. Indeed, we suggest that there is probably no single numerical metric that captures all aspects of sampling (1⁄4 rock volume, accessibility, effort), and recent attempts to correct the raw data, or to model sampling-driven patterns, may be premature. We then look at some case studies of patchy fossil records in taxa with good phylogenetic data, and suggest that in some cases at least the rock volume and fossil occurrence measures are identical, and so correlate almost perfectly. Finally, we suggest that such global-scale confrontations of sampling proxies and fossil data are not adequate at present, and recommend instead study-scale approaches to detect and correct sampling, involving direct evidence for missing data (e.g. Lazarus taxa; ghost ranges), direct evidence for sampling (e.g. number of localities or samples per time bin; fossil specimen completeness), and an integrated, model-based approach to incorporating sampling and explanatory models into explaining particular diversity curves. The fossil record, reality and sampling The fossil record, collector curves and

Rates of extinction vary greatly through geological time, with losses particularly concentrated in mass extinctions. Species duration at other times varies greatly, but the reasons for this are unclear. Geographical range correlates with lineage duration amongst marine invertebrates, but it is less clear how far this generality extends to other groups in other habitats. It is also unclear whether a wide geographical distribution makes groups more likely to survive mass extinctions. Here, we test for extinction selectivity amongst terrestrial vertebrates across the end-Triassic event. We demonstrate that terrestrial vertebrate clades with larger geographical ranges were more resilient to extinction than those with smaller ranges throughout the Triassic and Jurassic. However, this relationship weakened with increasing proximity to the end-Triassic mass extinction, breaking down altogether across the event itself. We demonstrate that these findings are not a function of sampling biases; a perennial issue in studies of this kind

Ichthyosaurs were highly successful marine reptiles with an abundant and well-studied fossil record. However, their occurrences through geological time and space are sporadic, and it is important to understand whether times of apparent species richness and rarity are real or the result of sampling bias. Here, we explore the skeletal completeness of 351 dated and identified ichthyosaur specimens, belonging to all 102 species, the first time that such a study has been carried out on vertebrates from the marine realm. No correlations were found between time series of different skeletal metrics and ichthyosaur diversity. There is a significant geographical variation in completeness, with the well-studied northern hemisphere producing fossils of much higher quality than the southern hemisphere. Medium-sized ichthyosaurs are significantly more complete than small or large taxa: the incompleteness of small specimens was expected, but it was a surprise that larger specimens were also relatively incomplete. Completeness varies greatly between facies, with fine-grained, siliciclastic sediments preserving the most complete specimens. These findings may explain why the ichthyosaur diversity record is low at times, corresponding to facies of poor preservation potential, such as in the Early Cretaceous. Unexpectedly, we find a strong negative correlation between skeletal completeness and sea level, meaning the most complete specimens occurred at times of global low sea level, and vice versa. Completeness metrics, however, do not replicate the sampling signal and have limited use as a global-scale sampling proxy.

The fossil record documents the history of life, but the reliability of that record has often been questioned. Spatiotemporal variability in sedimentary rock volume, sampling and research effort especially frustrates global-scale diversity reconstructions. Various proposals have been made to rectify palaeodiversity estimates using proxy measures for the availability and sampling of the rock record, but the validity of these approaches remains controversial. Targeting the rich fossil record of Great Britain as a highly detailed regional exemplar, our statistical analysis shows that marine outcrop area contains a signal useful for predicting changes in diversity, collections and formations, whereas terrestrial outcrop area contains a signal useful for predicting formations. In contrast, collection and formation counts are information redundant with fossil richness, characterized by symmetric, bidirectional information flow. If this is true, the widespread use of collection and formation counts as sampling proxies to correct the raw palaeodiversity data may be unwarranted., Palaeodiversity estimations are confounded by fossil availability and sampling. Here, Dunhill et al. use the fossil record of Great Britain to test aspects of the marine and terrestrial fossil records that are commonly used to identify and correct for bias in palaeodiversity estimations.