Article

New methods for quantifying macroevolutionary patterns and processes

December 2000
Paleobiology 26(4):707-733

December 2000
26(4):707-733

DOI:10.1666/0094-8373(2000)026<0707:NMFQMP>2.0.CO;2

Authors:

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.

The delayed rise of present-day mammals

Article

Full-text available

Mar 2007

Did the end-Cretaceous mass extinction event, by eliminating non-avian dinosaurs and most of the existing fauna, trigger the evolutionary radiation of present-day mammals? Here we construct, date and analyse a species-level phylogeny of nearly all extant Mammalia to bring a new perspective to this question. Our analyses of how extant lineages accumulated through time show that net per-lineage diversification rates barely changed across the Cretaceous/Tertiary boundary. Instead, these rates spiked significantly with the origins of the currently recognized placental superorders and orders approximately 93 million years ago, before falling and remaining low until accelerating again throughout the Eocene and Oligocene epochs. Our results show that the phylogenetic 'fuses' leading to the explosion of extant placental orders are not only very much longer than suspected previously, but also challenge the hypothesis that the end-Cretaceous mass extinction event had a major, direct influence on the diversification of today's mammals. Molecular data and the fossil record can give conflicting views of the evolutionary past. For instance, empirical palaeontological evidence by itself tends to favour the 'explosive model' of diversification for extant placental mammals 1 , in which the orders with living representatives both originated and rapidly diversified soon after the Cretaceous/Tertiary (K/T) mass extinction event that eliminated non-avian dinosaurs and many other, mostly marine 2 , taxa 65.5 million years (Myr) ago 1,3,4. By contrast, molecular data consistently push most origins of the same orders back into the Late Cretaceous period 5-9 , leading to alternative scenarios in which placental line-ages persist at low diversity for some period of time after their initial origins ('phylogenetic fuses'; see ref. 10) before undergoing evolutionary explosions 1,11. Principal among these scenarios is the 'long-fuse model' 1 , which postulates an extended lag between the Cretaceous origins of the orders and the first split among their living representatives (crown groups) immediately after the K/T boundary 8. Some older molecular studies advocate a 'short-fuse model' of diversification 1 , where even the basal crown-group divergences within some of the larger placental orders occur well within the Cretaceous period 5-7. A partial molecular phylogeny emphasizing divergences among placental orders suggested that over 20 lineages with extant descendants (henceforth, 'extant lineages') survived the K/T boundary 8. However, the total number of extant lineages that pre-date the extinction event and whether or not they radiated immediately after it remain unknown. The fossil record alone does not provide direct answers to these questions. It does reveal a strong pulse of diversification in stem eutherians immediately after the K/T boundary 4,12 , but few of the known Palaeocene taxa can be placed securely within the crown groups of extant orders comprising Placentalia 4. The latter only rise to prominence in fossils known from the Early Eocene epoch onwards (,50 Myr ago) after a major faunal reorganization 4,13,14. The geographical patchiness of the record complicates interpretations of this near-absence of Palaeocene crown-group fossils 14-16 : were these clades radiating throughout the Palaeocene epoch in parts of the world where the fossil record is less well known; had they not yet originated; or did they have very long fuses, remaining at low diversity until the major turnover at the start of the Eocene epoch? The pattern of diversification rates through time, to which little attention has been paid so far, might hold the key to answering these questions. If the Cretaceous fauna inhibited mammalian diversification , as is commonly assumed 1 , and all mammalian lineages were able to radiate after their extinction, then there should be a significant increase in the net per-lineage rate of extant mammalian diversification , r (the difference between the per-lineage speciation and extinction rates), immediately after the K/T mass extinction. This hypothesis, along with the explosive, long-and short-fuse models, can be tested using densely sampled phylogenies of extant species, which contain information about the history of their diversification rates 17-20. Using modern supertree algorithms 21,22 , we construct the first virtually complete species-level phylogeny of extant mammals from over 2,500 partial estimates, and estimate divergence times (with confidence intervals) throughout it using a 66-gene alignment in conjunction with 30 cladistically robust fossil calibration points. Our analyses of the supertree indicate that the principal splits underlying the diversification of the extant lineages occurred (1) from 100-85 Myr ago with the origins of the extant orders, and (2) in or after the Early Eocene (agreeing with the upturn in their diversity known from the fossil record 4,13,14), but not immediately after the K/T boundary, where diversification rates are unchanged. Our findings-that more extant placental lineages survived the K/T boundary than previously recognized and that fewer arose immediately after it than previously suspected-extend the phylogenetic fuses of many extant orders and indicate that the end-Cretaceous mass extinction event had, at best, a minor role in driving the diversification of the present-day mam-malian lineages. A supertree with divergence times for extant mammals The supertree contains 4,510 of the 4,554 extant species recorded in ref. 23, making it 99.0% complete at the species level (Fig. 1; see also

A review of the European Neogene Mammal zones from integration of litho-, bio- and magnetostratigraphy in the Teruel Basin

Article

Full-text available

Oct 2022
EARTH-SCI REV

The northern sector of the Teruel Basin (Spain) houses a dense and continuous record of late Neogene mammal fossil sites, as well as numerous biostratigraphic and magnetostratigraphic information making it a reference basin to define and refine the European mammal biostratigraphy from the Vallesian to the Villafranchian. The Neogene mammal chronology is in ongoing revision, and distinct correlations between basins and Europe provinces have been proposed based on their relative ages. New calibration methods based on numerical modelling have allowed the absolute ages of the paleontological sites to be refined. Nevertheless, some discrepancies arise, evidencing that anchoring between absolute ages and mammal fossil record would benefit from a stronger stratigraphical framework. This work provides such a robust 3D stratigraphic framework of the whole basin that, together with magnetostratigraphy, allows establishing an accurate chronostratigraphic model and hence a precise chronology of sedimentary units and mammal sites. The absolute age of MN zones, or mammal stages, in the Teruel Basin has been revised on the basis of a detailed and confident stratigraphic correlation, and updated to the most recent Geomagnetic Polarity Time Scale. In particular, new accurate ages have been proposed for the boundaries MN 9/10 to MN 16/17 from data exclusively located in the Teruel Basin, with a precision generally of 0.1–0.2 Ma.

Late Neogene to Early Quaternary climate evolution in southwestern Europe from a continental perspective

Article

Mar 2022
GLOBAL PLANET CHANGE

Paleoclimate reconstructions are mostly based on continuous oceanic records, but continental records, controlled by global and regional conditions, are paramount in identifying long- and short-term climatic variability between regions and investigating forcing mechanisms. Here we present a high-resolution lacustrine log from a western Mediterranean intramountain basin; it is based on calcite oxygen isotope composition (δ¹⁸Oc) and records detailed paleoclimatic information from the Late Miocene to the Early Pleistocene (9.8–1.8 Ma). Evidence is found for orbital forcing in the regional paleoclimate, with minimum and maximum eccentricity related to drier and wetter conditions respectively. Superimposed onto this variability, the long-term trend reflects the influence of global paleogeographic and climate change. Variations inferred in precipitation-evaporation (P–E) are related to SST in the North Atlantic, which evidences a connection between marine dynamics and continental climate in areas far from the coast in southwestern Europe and a relation between dry periods and high SST inland. It is proposed that the regional climate was impacted by the effect of the closure of the Central Atlantic Seaway and changes in the Atlantic Meridional Overturning Circulation (AMOC). Warmer/drier conditions were related to a more permanent, stable, high-pressure centre over the mid-Atlantic in a situation of strengthened AMOC, which would have blocked westerly winds, increasing aridity in southwestern Europe. The inferred warm/dry connection differs from other western Mediterranean records, supporting previous interpretations of a regional climate gradient in western Europe. As occurs at present, isolation from the influence of the humidity of the Mediterranean Sea during warm periods as a result of' to the local orography could well have been the cause of regional differences.

Taxonomic Inflation and Body Mass Distributions in North American Fossil Mammals

Article

May 2003

John Alroy

Body mass distributions of mammalian species are a major focus of macroecological and macroevolutionary studies. However, these distributions may be obscured by taxonomic error, just like any other aspect of biodiversity. The key problem with taxonomy is that many currently used names are synonyms of each other or are biologically indeterminate. This article reassesses body mass patterns in the fossil record of North American mammals using the recently developed flux ratio method for estimating the underlying proportion of invalid names. Current name quality varies very strongly with body mass: small species names are highly unreliable, but names of large species have been evaluated thoroughly. The main reason is that there has been a dramatic fall through historical time in the average size of described species. Hence, there simply has not been enough time yet to reevaluate the names of most small species. This bias only accentuates the previously described bimodal diversity distribution for North American mammals, which suggests the existence of dual body mass optima—so not all evolutionary lineages converge on 100 g. The historical shift in the underlying quality and body mass of newly described species also differentially affects our picture of biodiversity in major taxonomic groups. On the one hand, ungulate and carnivoran names are much more likely to be invalid in the 1st place than are rodent and insectivoran names. On the other hand, most of the invalid names for large mammals already have been identified, but this is not true for the small-mammal groups. Therefore, the most fruitful strategy for future taxonomic research would be to focus on small- and medium-sized mammals.

A framework for the integrated analysis of the magnitude, selectivity, and biotic effects of extinction and origination

Article

Full-text available

Oct 2019

The taxonomic and ecologic composition of Earth's biota has shifted dramatically through geologic time, with some clades going extinct while others diversified. Here, we derive a metric that quantifies the change in biotic composition due to extinction or origination and show that it equals the product of extinction/origination magnitude and selectivity (variation in magnitude among groups). We also define metrics that describe the extent to which a recovery (1) reinforced or reversed the effects of extinction on biotic composition and (2) changed composition in ways uncorrelated with the extinction. To demonstrate the approach, we analyzed an updated compilation of stratigraphic ranges of marine animal genera. We show that mass extinctions were not more selective than background intervals at the phylum level; rather, they tended to drive greater taxonomic change due to their higher magnitudes. Mass extinctions did not represent a separate class of events with respect to either strength of selectivity or effect. Similar observations apply to origination during recoveries from mass extinctions, and on average, extinction and origination were similarly selective and drove similar amounts of biotic change. Elevated origination during recoveries drove bursts of compositional change that varied considerably in effect. In some cases, origination partially reversed the effects of extinction, returning the biota toward the pre-extinction composition; in others, it reinforced the effects of the extinction, magnifying biotic change. Recoveries were as important as extinction events in shaping the marine biota, and their selectivity deserves systematic study alongside that of extinction.

Climate-driven ecological stability as a globally shared cause of Late Quaternary megafaunal extinctions: the Plaids and Stripes Hypothesis: A hypothesis about megafaunal extinctions

Article

Full-text available

Aug 2018

Controversy persists about why so many large‐bodied mammal species went extinct around the end of the last ice age. Resolving this is important for understanding extinction processes in general, for assessing the ecological roles of humans, and for conserving remaining megafaunal species, many of which are endangered today. Here we explore an integrative hypothesis that asserts that an underlying cause of Late Quaternary megafaunal extinctions was a fundamental shift in the spatio‐temporal fabric of ecosystems worldwide. This shift was triggered by the loss of the millennial‐scale climate fluctuations that were characteristic of the ice age but ceased approximately 11700 years ago on most continents. Under ice‐age conditions, which prevailed for much of the preceding 2.6 Ma, these radical and rapid climate changes prevented many ecosystems from fully equilibrating with their contemporary climates. Instead of today's ‘striped’ world in which species' ranges have equilibrated with gradients of temperature, moisture, and seasonality, the ice‐age world was a disequilibrial ‘plaid’ in which species' ranges shifted rapidly and repeatedly over time and space, rarely catching up with contemporary climate. In the transient ecosystems that resulted, certain physiological, anatomical, and ecological attributes shared by megafaunal species pre‐adapted them for success. These traits included greater metabolic and locomotory efficiency, increased resistance to starvation, longer life spans, greater sensory ranges, and the ability to be nomadic or migratory. When the plaid world of the ice age ended, many of the advantages of being large were either lost or became disadvantages. For instance in a striped world, the low population densities and slow reproductive rates associated with large body size reduced the resiliency of megafaunal species to population bottlenecks. As the ice age ended, the downsides of being large in striped environments lowered the extinction thresholds of megafauna worldwide, which then increased the vulnerability of individual species to a variety of proximate threats they had previously tolerated, such as human predation, competition with other species, and habitat loss. For many megafaunal species, the plaid‐to‐stripes transition may have been near the base of a hierarchy of extinction causes whose relative importances varied geographically, temporally, and taxonomically.

Spatial standardization of taxon occurrence data—a call to action

Article

Full-text available

Feb 2024

The fossil record is spatiotemporally heterogeneous: taxon occurrence data have patchy spatial distributions, and this patchiness varies through time. Large-scale quantitative paleobiology studies that fail to account for heterogeneous sampling coverage will generate uninformative inferences at best and confidently draw wrong conclusions at worst. Explicitly spatial methods of standardization are necessary for analyses of large-scale fossil datasets, because nonspatial sample standardization, such as diversity rarefaction, is insufficient to reduce the signal of varying spatial coverage through time or between environments and clades. Spatial standardization should control both geographic area and dispersion (spread) of fossil localities. In addition to standardizing the spatial distribution of data, other factors may be standardized, including environmental heterogeneity or the number of publications or field collecting units that report taxon occurrences. Using a case study of published global Paleobiology Database occurrences, we demonstrate strong signals of sampling; without spatial standardization, these sampling signatures could be misattributed to biological processes. We discuss practical issues of implementing spatial standardization via subsampling and present the new R package divvy to improve the accessibility of spatial analysis. The software provides three spatial subsampling approaches, as well as related tools to quantify spatial coverage. After reviewing the theory, practice, and history of equalizing spatial coverage between data comparison groups, we outline priority areas to improve related data collection, analysis, and reporting practices in paleobiology.

Body size estimation from isolated fossil bones reveals deep time evolutionary trends in North American lizards

Article

Full-text available

Jan 2024
PLOS ONE

Sara J Elshafie

Lizards play vital roles in extant ecosystems. However, their roles in extinct ecosystems are poorly understood because the fossil record of lizards consists mostly of isolated bones. This makes it difficult to document changes in lizard morphology and body size over time, which is essential for studies of lizard paleoecology and evolution. It is also difficult to compare available fossil lizard data with existing sources of extant lizard data because extant studies rarely measure individual bones. Furthermore, no previous study has regressed measurements of individual bones to body length across crown lizard groups, nor tested those regressions on fossil skeletons. An extensive dataset of individual bone measurements from extant lizards across crown taxonomic groups is here employed to develop novel methods for estimating lizard body size from isolated fossil elements. These methods were applied to a comparably large dataset of fossil lizard specimens from the robust Paleogene record (66–23 Ma) of the Western Interior of North America. This study tests the hypothesis that anatomical proportions have been conserved within higher-level crown lizard groups since the Paleogene and can therefore be used to reconstruct snout-vent length (SVL) and mass for fossil specimens referred to the same groups. Individual bones demonstrated strong correlation with SVL in extant as well as fossil lizard specimens ( R 2 ≥ 0.69). Equations for mass estimation from individual bones were derived from the SVL regressions using published equations for calculating lizard body mass from SVL. The resulting body size estimates from regression equations for the entire fossil dataset revealed that lizards reached greatest maximum body size in the middle Paleogene, with the largest size class dominated by anguid lizards that exceeded 1 meter in SVL and 1.5 kg in body mass. Maximum body size decreased to under 400 mm and below 1.5 kg in the late Paleogene. No association was found between changes in maximum lizard body size and marine isotope proxies of global temperature through the Paleogene. This is the first study to investigate body size evolution across lizard clades over a deep time interval and for a large geographic region. The proposed methods can be used to generate body size regressions and provide estimates of body size for isolated lizard bones referred to any crown group.

Spatial standardization of taxon occurrence data—a call to action

Preprint

Full-text available

Oct 2023

The fossil record is spatiotemporally heterogeneous: taxon occurrence data have patchy spatial distributions, and this patchiness varies through time. Inferences from large-scale quantitative paleobiology studies that fail to account for heterogeneous sampling coverage will be uninformative at best and confidently wrong at worst. Explicitly spatial methods of standardization are necessary for analyses of large-scale fossil datasets, because non-spatial sample standardization, such as diversity rarefaction, is insufficient to reduce the signal of varying spatial coverage through time or between environments and clades. Spatial standardization should control both geographic area and dispersion (spread) of fossil localities. In addition to spatial standardization, other factors may be standardized, including environmental heterogeneity or the number of publications or field collecting units that report taxon occurrences. Using a case study of published global Paleobiology Database occurrences, we demonstrate the strong signals of sampling that could be misinterpreted as biologically meaningful, and which spatial standardization accounts for successfully. We discuss practical issues of implementing spatial standardization via subsampling and present the new R package "divvy" to improve the accessibility of spatial analysis. The software provides three spatial subsampling approaches, as well as related tools to quantify spatial coverage. After reviewing the theory, practice, and history of equalizing spatial coverage between data comparison groups, we outline priority areas to improve related data collection, analysis, and reporting practices in paleobiology.

Untangling the web of life: reconstructing spatial patterns in the palaeoenvironment, palaeoecology and taphonomy of the Western Interior Seaway

Thesis

Jan 2019

Christopher David Dean

A central goal of palaeontology is determining trends in diversity through deep time, but our un- derstanding of these patterns is hampered by bias in the fossil record, arising from taphonomic, geological and anthropogenic causes. These factors can be further exacerbated by environments which are unqiue to the past. Epicontinental seas - shallow, continent covering oceans - were common throughout the Phanerozoic and contain the majority of our available fossil record. Their unique environmental conditions have led to the suggestion that their depositional pro- cesses, palaeo-community structure and taphonomic biases could be driven by different variables than those of otherwise time-equivalent shelf margin settings. Understanding this variation in both time and space is essential for bridging the gap in understanding between these environ- ments and the modern. In this thesis, a series of case studies attempt to understand the spatial patterns in palaeoenvironment, palaeoecology and taphonomy of the Western Interior Seaway, an epicontinental sea from the late Cretaceous of North America. A new method of estimat- ing palaeobathymetry using numerical tidal modelling reports that the seaway was deeper than previously suggested in the mid-Campanian, with tides within the 'Utah Bight' amplified by resonance effects. Analysis of palaeocommunity structure reveals that palaeobiogeography of molluscan fauna varies between the Cenomanian-Turonian and the lower Campanian; the for- mer exhibits a latitudinal gradient whilst the latter shows a homogeneous central seaway. As such, previous suggestions of distinct sub-provinces of fauna can be better explained by other palaeobiogeographic patterns. Differences in sampling probability between calcitic and aragonitic molluscs at varying depths suggest that preferential aragonite bias can be expressed spatially, potentially influencing the perceived range size of aragonitic organisms due to differences in between-site preservation. These studies show that it is important to understand the inherent spatial heterogeneity of the geological record to adequately analyse diversity patterns through time.

8. The Evolution of Sauropod Locomotion: Morphological Diversity of a Secondarily Quadrupedal Radiation

Chapter

Dec 2019

Matthew T Carrano

Pattern and Processes of the Mammalian Turnover of the Arikareean in the Northern Rocky Mountains

Article

Jul 2020

Jonathan Calede

The later part of the Oligocene (Arikareean North American Land Mammal Age) was a time of major faunal change in North America. It is during this time period that archaic mammalian faunas dominated by extinct families started giving way to more modern faunas, including families still extant today. Studies of this faunal transition have so far focused on the Great Plains and the Columbia Plateau. I present here the first quantitative analysis for the northern Rocky Mountains, combining four new radioisotopic dates and almost 1,000 specimens from a series of vertebrate microfossil assemblages through the Cabbage Patch beds of Montana. I demonstrate that the rise of modern mammalian communities was already under way in the Rocky Mountains 30 million years ago, at the base of the beds. However, the major faunal turnover event took place ca. 28 million years ago, at the transition from the lower to the middle units of the Cabbage Patch beds, and led to the disappearance of many archaic mammal taxa that dominated the start of the Arikareean. This event was synchronous across the Great Plains, the Rocky Mountains, and the Columbia Plateau and was driven by the diversification of descendants of immigrants from Eurasia that had reached North America through Beringia. Holdovers from archaic mammalian faunas persist into the upper unit of the beds later than in the Great Plains, but not the Columbia Plateau. Future biogeographic analyses will be necessary to assess the role of topography and environmental change in the rise of modern mammalian communities.

Fallout tuffs in the Eocene Duchesne River Formation, northeastern Utah—ages, compositions, and likely source

Article

Full-text available

Mar 2020

Thin fallout tuffs are common in the terrestrial deposits of the Eocene Duchesne River Formation on the flanks of the Uinta Mountains of eastern Utah. Their ages and compositions provide new insight into the tectonic events and magmatic history of the western Cordillera and provide important constraints on the Cenozoic land mammal chronology. Whole-rock compositions of the volcanic ash show that they underwent post-emplacement argillic alteration, typical of a wetland/floodplain depositional setting. However, immobile element ratios and abundances, such as Zr/Ti, La/Nb, and Y are typical of rhyolites formed in a subduction-related setting. Glass shards preserved in one sample all had SiO2 values >75%, typical of high-silica rhyolite. Preserved phenocrysts in the ash beds include quartz, sanidine, plagioclase, and biotite with variable amounts of accessory zircon, apatite, titanite, and allanite. Biotite compositions have Fe/(Fe+Mg) ratios typical of calc-alkaline igneous rocks and clusters of chemical compositions suggest a genetic relationship to three or four separate eruptions. Sanidine compositions from five samples range from Or73 and Or79. Only one sample had preserved plagioclase with compositions ranging between An22 – An49. Allanite from the ash beds has lower total rare earth elements (REE) concentrations than allanite from other well-studied rhyolites. Titanite in one sample has lower concentrations of REE, Fe, and Al than expected of rhyolites and is probably detrital. Plagioclase and sanidine from two different tuff beds near the middle of the Duchesne River Formation yielded analytically indistinguishable 40Ar/39Ar ages of 39.47 ± 0.16 Ma and 39.36 ± 0.15 Ma, respectively. These dates, along with the compositional data seem to limit the eruptive source for these fallout tuffs to the northeast Nevada volcanic field, one of the few volcanically active regions of western North America at the time. These new radiometric ages, along with stratigraphic relations and previously published ages for tuffs in the Bishop Conglomerate (which unconformably overlies the Duchesne River Formation), constrain the timing of late Laramide uplift in the region from 39 to about 37 Ma and post-Laramide epeirogenic uplift from 34 Ma to 30 Ma. Finally, the ages also provide additional evidence that the Duchesnean North American Land Mammal Age ended in the Eocene, which was originally named and defined from the Duchesne River Formation.

An analysis of the impacts of Cretaceous oceanic anoxic events on global molluscan diversity dynamics

Article

Full-text available

Apr 2019

Oceanic anoxic events (OAEs) are contemporaneous with 11 of the 18 largest Phanerozoic extinction events, but the magnitude and selectivity of their paleoecological impact remains disputed. OAEs are associated with abrupt, rapid warming and increased CO 2 flux to the atmosphere; thus, insights from this study may clarify the impact of current anthropogenic climate change on the biosphere. We investigated the influence of the Late Cretaceous Bonarelli event (OAE2; Cenomanian/Turonian stage boundary; ~94 Ma) on generic- and species-level molluscan diversity, extinction rates, and ecological turnover. Cenomanian/Turonian results were compared with changes across all Cretaceous stage boundaries, some of which are coincident with less severe OAEs. We found increased generic turnover, but not species-level turnover, associated with several Cretaceous OAEs. The absence of a species-level pattern may reflect species occurrence data that are too temporally coarse to robustly detect patterns. Five hypotheses of ecological selectivity relating anoxia to survivorship were tested across stage boundaries with respect to faunality, mobility, and diet using generalized linear models. Interestingly, benthic taxa were consistently selected against throughout the Cretaceous regardless of the presence or absence of OAEs. These results suggest that: (1) the Cenomanian/Turonian boundary (OAE2) was associated with a decline in molluscan diversity and increase in extinction rate that were significantly more severe than Cretaceous background levels; and (2) no differential ecological selectivity was associated with OAE-related diversity declines among the variables tested here.

An analysis of the impacts of Cretaceous oceanic anoxic events on global molluscan diversity dynamics

Article

Full-text available

Apr 2019
PALEOBIOLOGY

Oceanic anoxic events (OAEs) are contemporaneous with 11 of the 18 largest Phanerozoic extinction events, but the magnitude and selectivity of their paleoecological impact remains disputed. OAEs are associated with abrupt, rapid warming and increased CO 2 flux to the atmosphere; thus, insights from this study may clarify the impact of current anthropogenic climate change on the biosphere. We investigated the influence of the Late Cretaceous Bonarelli event (OAE2; Cenomanian/Turonian stage boundary; ∼94 Ma) on generic-and species-level molluscan diversity, extinction rates, and ecological turnover. Cenomanian/Turonian results were compared with changes across all Cretaceous stage boundaries, some of which are coincident with less severe OAEs. We found increased generic turnover, but not species-level turnover, associated with several Cretaceous OAEs. The absence of a species-level pattern may reflect species occurrence data that are too temporally coarse to robustly detect patterns. Five hypotheses of ecological selectivity relating anoxia to survivorship were tested across stage boundaries with respect to fau-nality, mobility, and diet using generalized linear models. Interestingly, benthic taxa were consistently selected against throughout the Cretaceous regardless of the presence or absence of OAEs. These results suggest that: (1) the Cenomanian/Turonian boundary (OAE2) was associated with a decline in molluscan diversity and increase in extinction rate that were significantly more severe than Cretaceous background levels; and (2) no differential ecological selectivity was associated with OAE-related diversity declines among the variables tested here.

Richness, Complementarity, and Community Structure of Amazonian Mammal Faunas: Results from Multiyear Inventories in French Guiana and Peru

Article

Full-text available

Jun 2024

Robert Voss

Evolutionary radiation strategy revealed in the Scarabaeidae with evidence of continuous spatiotemporal morphology and phylogenesis

Article

Full-text available

Jun 2024

Evolutionary biology faces the important challenge of determining how to interpret the relationship between selection pressures and evolutionary radiation. The lack of morphological evidence on cross-species research adds to difficulty of this challenge. We proposed a new paradigm for evaluating the evolution of branches through changes in characters on continuous spatiotemporal scales, for better interpreting the impact of biotic/abiotic drivers on the evolutionary radiation. It reveals a causal link between morphological changes and selective pressures: consistent deformation signals for all tested characters on timeline, which provided strong support for the evolutionary hypothesis of relationship between scarabs and biotic/abiotic drivers; the evolutionary strategies under niche differentiation, which were manifested in the responsiveness degree of functional morphological characters with different selection pressure. This morphological information-driven integrative approach sheds light on the mechanism of macroevolution under different selection pressures and is applicable to more biodiversity research.

Chronostratigraphy of Miocene strata in the Berkeley Hills (California Coast Ranges, USA) and the arrival of the San Andreas transform boundary

Article

Full-text available

Jan 2024
GEOSPHERE

Miocene strata of the Claremont, Orinda, and Moraga formations of the Berkeley Hills (California Coast Ranges, USA) record sedimentation and volcanism during the passage of the Mendocino triple junction and early evolution of the San Andreas fault system. Detrital zircon laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) age spectra indicate a change in sedimentary provenance between the marine Claremont formation (Monterey Group) and the terrestrial Orinda and Moraga Formations associated with uplift of Franciscan Complex lithologies. A sandstone from the Claremont formation produced a detrital zircon chemical abrasion–isotope dilution–thermal ionization mass spectrometry (CA-ID-TIMS) maximum depositional age of 13.298 ± 0.046 Ma, indicating younger Claremont deposition than previously interpreted. A trachydacite tuff clast within the uppermost Orinda Formation yielded a CA-ID-TIMS U-Pb zircon date of 10.094 ± 0.018 Ma, and a dacitic tuff within the Moraga Formation produced a CA-ID-TIMS U-Pb zircon date of 9.974 ± 0.014 Ma. These results indicate rapid progression from subsidence in which deep-water siliceous sediments of the Claremont formation were deposited to uplift that was followed by subsidence during deposition of terrestrial sediments of the Orinda Formation and subsequent eruption of the Moraga Formation volcanics. We associate the Orinda tuff clast and Moraga volcanics with slab-gap volcanism that followed the passage of the Mendocino triple junction. Given the necessary time lag between triple junction passage and the removal of the slab that led to this volcanism, subsidence associated with ca. 13 Ma Claremont sedimentation and subsequent Orinda to Moraga deposition can be attributed to basin formation along the newly arrived transform boundary.

Evolution of Cenozoic Land Mammal Faunas and Ecosystems

Book

Aug 2023

This volume presents an array of different case studies which take as primary material data sourced from the NOW (‘New and Old Worlds’) database of fossil mammals. The NOW database was one of the very first large paleobiological databases, and since 1996 it has been expanded from including mainly Neogene European land mammals to cover the entire Cenozoic at a global scale. In the last two decades the number of works that are based in the use of huge databases to explore ecological and evolutionary questions has increased exponentially, and even though the importance of big data in paleobiological research has been outlined in selected chapters of general works, no volume has appeared before this one which solely focuses on the databases as a primary source in reconstructing the past. The purpose of this book is to provide an illustrative volume showing the importance of big data in paleobiological research, and presenting a broad array of unpublished examples and case studies. The book is mainly aimed to professional palaeobiologists working with Cenozoic land mammals, but the scope of the book is broad enough to fit the interest for evolutionary biologists, paleoclimatologists and paleoecologists. The volume is divided in four parts. The first part includes two chapters on the development of large paleobiological databases, providing a first-hand account on the logic and the functioning of these databases. This is a much-needed perspective which is ignored by most researchers and users of such databases and, even if centered in the NOW database, the lessons that can be learned from this part can be extended to other examples. After this introductory part, the body of the book follows and is divided into three parts: patterns in regional faunas; large scale patterns and processes; and ecological, biogeographical and evolutionary patterns of key taxa. Each chapter is written by well-known specialists in the field, with some participation of members of the NOW advisory board. The array of selected mammal taxa ranges from carnivores, equids, ruminants and rodents to the genus Homo. The topics studied also include the diversification and radiation of major clades, large-scale paleobiogeographical patterns, the evolution of ecomorphological patterns and paleobiological problems such as evolution of body size or species longevity. In most cases the results are discussed in relation to protracted environmental or paleogeographic changes.

Live Long and Prosper? Assessing Longevity of Small Mammal Taxa Using the NOW Database

Chapter

Full-text available

Aug 2023

Extinction is part of life. Some groups persist longer than others, as is confirmed in an analysis of the small mammal data in the NOW database. Longevities are shorter in Rodentia than in Eulipotyphla and Lagomorpha. At the family level, the shortest longevities both for genera and species lies with the most diverse groups, whereas families with low diversity tend to have a longer duration of their representatives. This suggests that competition between phylogenetically related species creates Red Queen dynamics that lead to a shorter duration of (chrono)-species in the more diverse groups, whereas taxa that have little competition can persist for a much longer time.KeywordsCompetitionDiversityEulipotyphlaExtinctionLagomorphaRodentia

Regional Topography and Climate Influence the Nature and Timing of Changes in the Structure of Rodent and Lagomorph Faunas Through the Cenozoic of North America

Chapter

Aug 2023

Recent studies have demonstrated dramatic changes in North American rodent and lagomorph faunas through the Cenozoic, with open-habitat specialists (characterized by increased tooth crown height and adaptations for burrowing, jumping, or running) becoming common as open and arid habitats spread. These studies have primarily focused on continental scale analyses, but comparisons of regional and local scale changes are key to understanding how individual faunas changed over time and the roles exerted by topography and local climatic conditions on these faunal changes. Here, we use a database of all fossil rodents and lagomorphs in North America modified from NOW, MIOMAP, and FAUNMAP to compare faunas through time across nine distinct regions. Our analyses reveal asynchronous changes across the continent, with specialized dietary and locomotor adaptations in rodents and lagomorphs occurring earlier in relatively cool, arid regions at higher latitudes. Findings suggest topographic complexity and volcanic activity potentially drove aspects of ecomorphological evolution in rodents and lagomorphs. The attributes of open and arid-adapted taxa likely facilitated their spread from tectonically and volcanically active regions across the continent, as environmental conditions changed through the Cenozoic.KeywordsClimate changeHypsodontyMammal FaunasNorth AmericaRodentiaLagomorpha

Mechanistic neutral models show that sampling biases drive the apparent explosion of early tetrapod diversity

Article

Full-text available

Jul 2023
Nat. Ecol. Evol.

Estimates of deep-time biodiversity typically rely on statistical methods to mitigate the impacts of sampling biases in the fossil record. However, these methods are limited by the spatial and temporal scale of the underlying data. Here we use a spatially explicit mechanistic model, based on neutral theory, to test hypotheses of early tetrapod diversity change during the late Carboniferous and early Permian, critical intervals for the diversification of vertebrate life on land. Our simulations suggest that apparent increases in early tetrapod diversity were not driven by local endemism following the ‘Carboniferous rainforest collapse’. Instead, changes in face-value diversity can be explained by variation in sampling intensity through time. Our results further demonstrate the importance of accounting for sampling biases in analyses of the fossil record and highlight the vast potential of mechanistic models, including neutral models, for testing hypotheses in palaeobiology.

Advances in the Understanding of Neogene Mammalian Fauna in the Pampean Region (Central Argentina) Through Revising “Biozone” Hypotheses Based on New Dates and Biochronological Analyses

Article

Jul 2023
Ameghiniana

Fossil vertebrates, especially mammals, of the Neogene–Quaternary of Central Argentina were fundamental to the construction of time and rock-time scales and the knowledge of the biotic evolution of southern South America. The poverty of fossiliferous localities constrained with radiometric and/or paleomagnetic data heavily complicated the correlation of different faunas and their temporal allocation. The Cerro Azul Formation (Argentina) constitutes a suitable example of this situation but also enlarged because its fossils have been collected from scattered and isolated small outcrops whose chronological ordering was based on the “stage of evolution” of some rodents. We present here new dates for the fauna/locality of Telén (La Pampa Province) plus extensive biochronological analyses covering 16 fossiliferous localities referred to Cerro Azul Formation. Two dates from an “escoria” sample gave 7.09 Ma for Telén assemblage, an age in accordance with that obtained from an independent faunal analysis. Faunal ordination and age obtained with regression analyses identify a succession of faunas/localities that cover the time range between 8–5.33 Ma. The older assemblages (e.g., Cerro Bota) appear to be transitional between Chasicoan and “Huayquerian” faunas. The first records of procyonids and cricetid rodents, two North American lineages, are not synchronic (7 and 5.7 Ma, respectively). Our results show important temporal overlapping among the supposed successive rodent “biozones.” The use of the “stage of evolution” in the analyses does not improve the results strongly suggesting their inconvenience when is applied without independent chronological/biostratigraphical constraints.

No (Cambrian) explosion and no (Ordovician) event: A single long-term radiation in the early Palaeozoic

Article

Apr 2023
PALAEOGEOGR PALAEOCL

Estimating Rates and Probabilities of Origination and Extinction Using Taxonomic Occurrence Data: Capture-Mark-Recapture (CMR) Approaches

Article

Jul 2017

We rely on observations of occurrences of fossils to infer the rates and timings of origination and extinction of taxa. These estimates can then be used to shed light on questions such as whether extinction and origination rates have been higher or lower at different times in earth history or in different geographical regions, etc. and to investigate the possible underlying causes of varying rates. An inherent problem in inference using occurrence data is one of incompleteness of sampling. Even if a taxon is present at a given time and place, we are guaranteed to detect or sample it less than 100% of the time we search in a random outcrop or sediment sample that should contain it, either because it was not preserved, it was preserved but then eroded, or because we simply did not find it. Capture-mark-recapture (CMR) methods rely on replicate sampling to allow for the simultaneous estimation of sampling probability and the parameters of interest (e.g. extinction, origination, occupancy, diversity). Here, we introduce the philosophy of CMR approaches especially as applicable to paleontological data and questions. The use of CMR is in its infancy in paleobiological applications, but the handful of studies that have used it demonstrate its utility and generality. We discuss why the use of CMR has not matched its development in other fields, such as in population ecology, as well as the importance of modelling the sampling process and estimating sampling probabilities. In addition, we suggest some potential avenues for the development of CMR applications in paleobiology.

Development of Cenogram Technique Over the Past Six Decades with Some Insights into the Varied Habitats Occupied by Diverse Mammalian Communities Across Spain, China, and India Transiting the Middle Miocene Climatic Optimum

Chapter

Jan 2023

The climatic evolution of the Neogene, with long-term cooling disrupted by the Middle Miocene Climatic Optimum (MMCO; ~17–14.75 Ma), arises as a suitable baseline to analyze the effects of these transcendent climatic changes on the mammalian community structures. The present investigation is an attempt to examine the palaeohabitat of a Neogene (Middle Miocene: ~15–11.5 Ma) geographically distant (i.e., from Spain, China, and India) extinct mammalian communities utilizing the cenogram approach (in both qualitative and quantitative framework). The detailed statistical analyses (presented herein) incorporating a total of eight mammalian communities allows us to infer predominance of Tropical Deciduous Forest environments between ~15 and ~11.5 Ma interval, with several pulses of distinctive aridity experienced by some communities thriving within the Iberian region. On the contrary, stable forested conditions were witnessed by the middle Miocene communities of Asia [i.e., the ~11.5 million-year-old mammalian community of Laogou (China), and the ~13.5 million-year-old mammalian community of Ramnagar (north India)]. Our present investigation also infers that additional mammalian remains (particularly of body mass of <35 kg) are warranted to decipher the habitat (based on cenogram approach) of the Middle Miocene (~13 Ma) mammalian community of Kalagarh (Himalayan Foreland Basin, north India) and the Middle Miocene (~14 Ma) mammalian community of Palasava (Kutch Basin, western India). Nonetheless, the Cenogram technique (being continuously developed over the past six decades) may become an important tool to decipher any habitat change(s) of western India’s mammalian communities considering renewed palaeontological efforts within the Neogene of the region.KeywordsCenogram analysisNeogeneMammalsPalaeoenvironmentPalaeohabitat

Recommender systems for fossil community distribution modelling

Article

Full-text available

Jun 2022
Methods Ecol. Evol.

Indre Zliobaite

We propose to leverage recommender systems from machine learning to build large‐scale community distribution models for the mammalian fossil record. Recommender systems are behind most online life today, from shopping to news personalisation, online dating, or the selection of study programmes or fastest routes. Many recommender systems work by predicting user preferences from items that occur together in user profiles. Technically, this setting closely resembles co‐occurrence of species in natural environments. Here we frame community distribution modelling as a recommender systems task, tailor existing recommender techniques for this purpose and propose optimisation criteria for fitting the models in the ecological context. The predictive power comes from species co‐occurrences. We demonstrate the potential of this approach for analysing past ecosystems on a case study of Miocene fossil sites in Europe, where we use the proposed community distribution modelling for reconstructing companionships and relative abundances of large mammals. The proposed approach to community distribution modelling, although not climatically explicit, can help to reconstruct past ecosystems and analyse their structure and dynamics over time and space. It also allows, even coarsely, to predict relative abundances of fossil species from presence–absence data. More generally, the proposed perspective is a means for analysis of fossil communities and the relationships between their ecological contexts.

Early tetrapod diversification under neutral theory

Preprint

Full-text available

Feb 2022

Estimates of deep-time biodiversity typically rely on statistical methods to mitigate the impacts of sampling biases in the fossil record. However, these methods are limited by the spatial and temporal scale of the underlying data. Here, we use a spatially explicit mechanistic model, based on neutral theory, to test hypotheses of early tetrapod diversity change during the late Carboniferous and early Permian, critical intervals for the diversification of vertebrate life on land. Our neutral simulations suggest, in contrast to previous studies, that increases in early tetrapod diversity were not driven by local endemism following the 'Carboniferous Rainforest Collapse'. We show that apparent changes in face-value diversity can instead be explained by variation in sampling intensity through time. Our results further demonstrate the importance of accounting for sampling biases in analyses of the fossil record and demonstrate the vast potential of mechanistic models, including neutral models, for testing hypotheses in palaeobiology.

3. Phylogenetic and Taxic Perspectives on Sauropod Diversity

Chapter

Dec 2019

New radiometric 40Ar–39Ar dates and faunistic analyses refine evolutionary dynamics of Neogene vertebrate assemblages in southern South America

Article

Full-text available

May 2021

The vertebrate fossil record of the Pampean Region of Argentina occupies an important place in South American vertebrate paleontology. An abundance of localities has long been the main basis for constructing the chronostratigraphical/geochronological scale for the late Neogene–Quaternary of South America, as well as for understanding major patterns of vertebrate evolution, including the Great American Biotic Interchange. However, few independently-derived dates are available for constraining this record. In this contribution, we present new 40Ar/39Ar dates on escorias (likely the product of meteoric impacts) from the Argentinean Atlantic coast and statistically-based biochronological analyses that help to calibrate Late Miocene–Pliocene Pampean faunal successions. For the type areas of the Montehermosan and Chapadmalalan Ages/Stages, our results delimit their age ranges to 4.7–3.7 Ma and ca. 3.74–3.04 Ma, respectively. Additionally, from Buenos Aires Province, dates of 5.17 Ma and 4.33 Ma were recovered for “Huayquerian” and Montehermosan faunas. This information helps to better calibrate important first appearances of allochthonous taxa in South America, including one of the oldest records for procyonids (7.24–5.95 Ma), cricetids (6.95–5.46 Ma), and tayassuids (> 3.74 Ma, oldest high-confidence record). These results also constrain to ca. 3 Ma the last appearances of the autochthonous sparassodonts, as well as terror birds of large/middle body size in South America. South American faunal turnover during the late Neogene, including Late Pliocene extinctions, is interpreted as a consequence of knock-on effects from global climatic changes and initiation of the icehouse climate regime.

Componentes filogenéticos y ecológicos de la variación morfológica del cráneo de mamíferos

Book

Nov 2019

Jimena Bohórquez-Herrera

PROLOGO Los vertebrados son abundantes y visibles en la experiencia de las personas del mundo natural, al mencionar la palabra animal es común que estas asocien el concepto a un vertebrado y usualmente a un mamífero. Los vertebrados son también notablemente diversos, a partir del registro fósil se puede rastrear la evolución a lo largo de 150 millones de años de mamíferos desde sus pequeños antepasados ectotérmicos y sin pelo hasta los mamíferos endotérmicos y peludos. Las estructuras del cráneo y especialmente los dientes de mamíferos son los fósiles más abundantes, y es en estas estructuras que los científicos han basado sus estudios sobre los procesos evolutivos de estos animales. El cráneo de los mamíferos se ha estudiado, durante décadas, en sus variadas componentes funcionales, en los últimos años ha integrado a estos estudios los componentes filogenéticos y ecológicos, los cuales aportan a la comprensión de los patrones de la variabilidad morfológica, esta es la temática principal del presente libro, donde la Dra. Jimena Bohórquez mediante un enfoque integrador y examinando las técnicas más recientes ecomorfológicas y filogenéticas, nos presenta detalladamente en el desarrollo del libro estudios desde la convergencia evolutiva craneal hasta los procesos adaptativos que modelan las interacciones ecomorfológicas de los mamíferos actuales, lo cual está estrechamente ligado a la línea de investigación de la Dra. Bohórquez quien ha realizado estudios en esta área desde su pregrado en biología marina, seguido de sus estudios en ecomorfología de vertebrados marinos realizados tanto de maestría, doctorales, y a lo largo de su carrera profesional. Dr. Hugo A. Benítez Laboratorio de Ecología y Morfometría Evolutiva Universidad Católica del Maule, Chile

The effects of geographic range size and abundance on extinction during a time of “sluggish”’ evolution

Article

Full-text available

Dec 2020

Geographic range size and abundance are important determinants of extinction risk in fossil and extant taxa. However, the relationship between these variables and extinction risk has not been tested extensively during evolutionarily “quiescent” times of low extinction and speciation in the fossil record. Here we examine the influence of geographic range size and abundance on extinction risk during the late Paleozoic (Mississippian–Permian), a time of “sluggish” evolution when global rates of origination and extinction were roughly half those of other Paleozoic intervals. Analyses used spatiotemporal occurrences for 164 brachiopod species from the North American midcontinent. We found abundance to be a better predictor of extinction risk than measures of geographic range size. Moreover, species exhibited reductions in abundance before their extinction but did not display contractions in geographic range size. The weak relationship between geographic range size and extinction in this time and place may reflect the relative preponderance of larger-ranged taxa combined with the physiographic conditions of the region that allowed for easy habitat tracking that dampened both extinction and speciation. These conditions led to a prolonged period (19–25 Myr) during which standard macroevolutionary rules did not apply.

The measurement of species selection on evolving characters

Preprint

Full-text available

Aug 2017

Carl Simpson

Many processes can contribute to macroevolutionary change. This fact is the source of the wide variety of macroevolutionary change across time and taxa as well as the bane of pale-obiological research trying to understand how macroevolution works. Here, I present a general framework for understanding the variety of macroevolutionary phenomena. Based on Price’s theorem, this framework provides a simple quantitative means to understand (1) the macroevolutionary processes that are possible and (2) the way those processes interact with each other. The major qualitative features of macroevolution depend first on the number of processes that co-occur and then on the magnitudes and evolutionary directions of those processes. Species selection, the major macroevolutionary process, consists of patterns of differential rates of speciation and extinction. Its macroevolutionary efficacy depends on the presences of sufficient microevolutionary change. Conversely, microevolutionary change is limited in power by the independent evolution of species, and species selection acting across populations of species can amplify or suppress microevolution. Non-trends may result if species selection sufficiently neutralizes microevolution and may yield stable macroevolutionary patterns over many millions of years.

Cenogram analyses as habitat indicators for Paleogene–Neogene mammalian communities across the globe, with an emphasis on the early Eocene Cambay Shale mammalian community from India.

Article

Jul 2020

The present study is an attempt to utilize cenogram methodology (both qualitative and quantitative) to consider mammalian communities from five early to late Eocene localities across the globe (i.e., Polecat Bench, Bighorn Basin, North America; Abbey Wood, Blackheath Formation, UK; Cambay Shale, Cambay Basin, India; Wutu Formation, Wutu Basin, China; Pondaung Formation, Myanmar) so as to provide a comparative palaeohabitat framework. It is also a first attempt to examine the palaeohabitat of an extinct mammalian community (i.e., from Cambay Shale) in India utilizing the cenogram approach. In addition, seven extinct middle-Miocene communities (Laogou, Linxia Basin, China; Estación Imperial, Spain; Paseo de las Acacias, Spain; Arroyo del Olivar-Puente de Vallecas, Spain; Somo-saguas, Spain; Paracuellos 5, Spain; Paracuellos 3, Spain) have also been considered, in order to provide a global perspective to the climatic inferences in a temporal context. The majority of statistical calculations for Paleogene communities expose forested and humid conditions, excluding the Cambay Shale mammalian community of India. A hidden diversity within the medium to large body-size category of mammals (disguising the mammal biodiversity expected in tropical forested habitats) from Cambay Shale (western India) is a plausible cause of digression in the results. This is reflected in the histograms showing relationships between proportions of mammal species in various body-mass categories. Furthermore, the results show that Neogene mammalian communities were sustained in comparatively open habitats. Differences between occidental European and Asian localities in the canopy and humidity of the Neogene environments are also reflected in our analyses.

Paleosol-based inference of niches for Oligocene and early miocene fossils from the John Day Formation of Oregon

Article

Jun 2020

Over the past decade, we recorded exact locations of in situ fossils and measured calcareous nodules in paleosols of the Oligocene and lower Miocene (Whitneyan–Arikareean) John Day Formation of Oregon. These data enable precise biostratigraphy within an astronomical time scale of Milankovitch obliquity cycles and also provide mean annual precipitation and vegetation for each species. Fossils in paleosols of the John Day Formation alternated between semiarid shrubland and subhumid woodland communities every 41 ka. Land snails ‘Polygyra’ expansa and Monadenia dubiosa were found in semiarid paleosols, but Vespericola dalli and Monadenia marginicola were found in subhumid paleosols. Cicada burrows (Naktodemasis bowni) were found in semiarid paleosols, whereas dung beetle balls (Pallichnus dakotensis) and earthworm castings (Edaphichnium lumbricatum) were found in subhumid paleosols. Among hypertragulids, Hypertragulus hesperius was found in semiarid paleosols and Nanotragulus planiceps in subhumid paleosols. Among glires, the aplodontiid Haplomys liolophus, geomyids Pleurolicus sulcifrons and several species of Entoptychus, castorid Palaeocastor peninsulatus, and leporid Archaeolagus ennisianus were found in semiarid paleosols. Large ungulates were found primarily in subhumid paleosols, including the agriochoere Agriochoerus antiquus, oreodonts Eporeodon occidentalis and Promerycochoerus superbus, equid Miohippus annectens, and rhinos Diceratherium annectens and Diceratherium armatum. The inferred niches of fossil mammals are consistent with interpretations based on their morphology; taxa with adaptations for life in open, arid habitats, such as high-crowned teeth and semifossorial or cursorial limb structure, were mainly in semiarid paleosols, but taxa with arboreal adaptations were only found in subhumid paleosols.

How predictable is extinction? Forecasting species survival at million-year timescales

Article

Full-text available

Nov 2019

A tenet of conservation palaeobiology is that knowledge of past extinction patterns can help us to better predict future extinctions. Although the future is unobservable, we can test the strength of this proposition by asking how well models conditioned on past observations would have predicted subsequent extinction events at different points in the geological past. To answer this question, we analyse the well-sampled fossil record of Cenozoic planktonic microfossil taxa (Foramanifera, Radiolaria, diatoms and calcareous nanoplankton). We examine how extinction probability varies over time as a function of species age, time of observation, current geographical range, change in geographical range, climate state and change in climate state. Our models have a 70–80% probability of correctly forecasting the rank order of extinction risk for a random out-of-sample species pair, implying that determinants of extinction risk have varied only modestly through time. We find that models which include either historical covariates or account for variation in covariate effects over time yield equivalent forecasts, but a model including both is overfit and yields biased forecasts. An important caveat is that human impacts may substantially disrupt range-risk dynamics so that the future will be less predictable than it has been in the past. This article is part of a discussion meeting issue ‘The past is a foreign country: how much can the fossil record actually inform conservation?’

The accelerating influence of humans on mammalian macroecological patterns over the late Quaternary

Article

May 2019
QUATERNARY SCI REV

The transition of hominins to a largely meat-based diet ∼1.8 million years ago led to the exploitation of other mammals for food and resources. As hominins, particularly archaic and modern humans, became increasingly abundant and dispersed across the globe, a temporally and spatially transgressive extinction of large-bodied mammals followed; the degree of selectivity was unprecedented in the Cenozoic fossil record. Today, most remaining large-bodied mammal species are confined to Africa, where they co-evolved with hominins. Here, using a comprehensive global dataset of mammal distribution, life history and ecology, we examine the consequences of ‘body size downgrading’ of mammals over the late Quaternary on fundamental macroecological patterns. Specifically, we examine changes in species diversity, global and continental body size distributions, allometric scaling of geographic range size with body mass, and the scaling of maximum body size with area. Moreover, we project these patterns toward a potential future scenario in which all mammals currently listed as vulnerable on the IUCN's Red List are extirpated. Our analysis demonstrates that anthropogenic impact on earth systems predates the terminal Pleistocene and has grown as populations increased and humans have become more widespread. Moreover, owing to the disproportionate influence on ecosystem structure and function of megafauna, past and present body size downgrading has reshaped Earth's biosphere. Thus, macroecological studies based only on modern species yield distorted results, which are not representative of the patterns present for most of mammal evolution. Our review supports the concept of benchmarking the ‘Anthropocene’ with the earliest activities of Homo sapiens.

Quantifying the community turnover of the uppermost Wenlock and Ludlow (Silurian) conodonts in the Baltic Basin

Article

Full-text available

Mar 2019
PALAEOGEOGR PALAEOCL

The Homerian to Ludfordian interval of the mid to late Silurian Period was a time of significant changes in conodont communities, global climate, oceanographic patterns and biogeochemical cycles. The Mulde and the Lau events are preeminent examples of globally recognized conodont extinction episodes from this interval in Earth’s history. The Silurian Baltic Basin is the most suitable locality, globally, for studying these perturbations to the ocean-atmosphere system, since there is an extensive record of conodont taxa ocurrences, their communities, and their environments spanning across shore-face to open-ocean settings. In this study, we present new conodont and �13C data from the upper Homerian to Ludlow interval from two core sections – G˙eluva-99 and G˙eluva-118, representing shelfal environments, and the numerical conodont data from the Vidukl˙e-61 section, from deep-water settings, and compare them with patterns of conodont diversity change, as revealed in the data-rich Milaiciai-103 core section. For this purpose, we explored the stratigraphically tied time series of conodont diversity changes employing recurrence and cross-recurrence plots – the binary similarity matrices that are used for deciphering complex spatial and temporal dynamic patterns. The cross-recurrence plots were used as a means of synchronizing the geological sections by applying dynamic time warping and the newly described moving window median recurrence point search algorithms. The results revealed that the conodont community compositional data are sufficiently temporally and spatially coherent to be reasonably used for synchronizing geological records. Moreover, the sudden state transitions detected in the cross-recurrence plots suggest that the Lau Event was of great importance for conodont community evolution in the studied time slice.

After the mammoths: The ecological legacy of late Pleistocene megafauna extinctions

Article

Full-text available

Feb 2023

The significant extinctions in Earth history have largely been unpredictable in terms of what species perish and what traits make species susceptible. The extinctions occurring during the late Pleistocene are unusual in this regard, because they were strongly size-selective and targeted exclusively large-bodied animals (i.e., megafauna, >1 ton) and disproportionately, large-bodied herbivores. Because these animals are also at particular risk today, the aftermath of the late Pleistocene extinctions can provide insights into how the loss or decline of contemporary large-bodied animals may influence ecosystems. Here, we review the ecological consequences of the late Pleistocene extinctions on major aspects of the environment, on communities and ecosystems, as well as on the diet, distribution and behavior of surviving mammals. We find the consequences of the loss of megafauna were pervasive and left legacies detectable in all parts of the Earth system. Furthermore, we find that the ecological roles that extinct and modern megafauna play in the Earth system are not replicated by smaller-bodied animals. Our review highlights the important perspectives that paleoecology can provide for modern conservation efforts.

New specimens of middle Eocene omomyines (Primates, Omomyoidea) from the Uinta Basin of Utah and the Tornillo Basin of Texas, with clarification of the generic status of Ourayia, Mytonius, and Diablomomys

Article

Oct 2023
J HUM EVOL

Volume References

Book

May 2022

Humans evolved in the dynamic landscapes of Africa under conditions of pronounced climatic, geological and environmental change during the past 7 million years. This book brings together detailed records of the paleontological and archaeological sites in Africa that provide the basic evidence for understanding the environments in which we evolved. Chapters cover specific sites, with comprehensive accounts of their geology, paleontology, paleobotany, and their ecological significance for our evolution. Other chapters provide important regional syntheses of past ecological conditions. This book is unique in merging a broad geographic scope (all of Africa) and deep time framework (the past 7 million years) in discussing the geological context and paleontological records of our evolution and that of organisms that evolved alongside our ancestors. It will offer important insights to anyone interested in human evolution, including researchers and graduate students in paleontology, archaeology, anthropology and geology.

Rapoport effects are inconsistently demonstrated through time

Article

Jul 2021
PALAEOGEOGR PALAEOCL

Tom Radomski

A Rapoport effect is a pattern in which species' geographic range sizes increase toward the poles. Previous work suggested that Pleistocene glaciation caused the extinction of small-ranging species at higher latitudes, resulting in a Rapoport effect among North American mammals. If caused by glaciation, Rapoport effects should be apparent in Pleistocene Europe, where glaciers advanced relatively far south, but not in Asia, where glacial advance was much more limited. Variation in geographic range size in the fossil record of Cenozoic mammals of Europe was quantified, binning fossils into European land mammal ages. Next, the same was done for Cenozoic mammals of Asia, binning by Asian land mammal ages and China faunal ages. By requiring a minimum sample size of ten points to estimate range size, most time bins on either continent were too insufficiently sampled to assess Rapoport effects. A Rapoport effect was found for four of twelve European land mammal ages, but cooling was associated with only one Rapoport effect. A Rapoport effect was never recovered in Asia. After scrutinizing the evidence for North American Rapoport effects among fossil mammals, the overall evidence for glaciation driving Rapoport effects is scant. Support for glaciation causing Rapoport effects is questioned.

Composite Time Lines: A Means to Leverage Resolving Power from Radioisotopic Dates and Biostratigraphy

Article

Oct 2006

Peter M. Sadler

Species origination and extinction events far outnumber radioisotopically dated events in the ancient stratigraphic record. In order to calibrate rapid rates of Mesozoic and Paleozoic change and to estimate the ages of paleobiologic events it would be ideal to have multiple dated events in single stratigraphic sections. This condition is rarely realized and the practical alternative is to build composite sections that combine information from many different locations. The compositing process takes advantage of all available evidence of relative age to produce high resolution time lines; i.e. ordered sequences of individual events whose average spacing is much finer than the duration of biostratigraphic zones and can approach the uncertainty intervals of the highest precision radioisotopic dates. Dated events are included in the compositing process from the outset. As a result the sequencing procedure is more efficient and the dated events find their optimal positions in the time line independent of any biostratigraphic zonal schemes. The sequencing procedures follow simple logical rules that may be learned from tiny data sets. When usefully large numbers of events are involved, however, the sequencing must be undertaken by computer and there is seldom a unique solution that best fits the field data. The range of positions in sequence that an event may occupy across the full set of equally best-fit solutions is a measure of the resolving power of the event. As new high-precision dates and detailed range charts continue to become available, the quality of the time lines will improve and they will become increasingly viable alternatives to zonal time scales in the older parts of the Phanerozoic.

Formation binning: a new method for increased temporal resolution in regional studies, applied to the Late Cretaceous dinosaur fossil record of North America

Article

Full-text available

Jun 2020

The advent of palaeontological occurrence databases has allowed for detailed reconstruction and analyses of species richness through deep time. While a substantial literature has evolved ensuring that taxa are fairly counted within and between different time periods, how time itself is divided has received less attention. Stage‐level or equal‐interval age bins have frequently been used for regional and global studies in vertebrate palaeontology. However, when assessing diversity at a regional scale, these resolutions can prove inappropriate with the available data. Herein, we propose a new method of binning geological time for regional studies that intrinsically incorporates the chronostratigraphic heterogeneity of different rock formations to generate unique stratigraphic bins. We use this method to investigate the diversity dynamics of dinosaurs from the Late Cretaceous of the Western Interior of North America prior to the Cretaceous–Palaeogene mass extinction. Increased resolution through formation binning pinpoints the Maastrichtian diversity decline to between 68 and 66 Ma, coinciding with the retreat of the Western Interior Seaway. Diversity curves are shown to exhibit volatile patterns using different binning methods, supporting claims that heterogeneous biases in this time‐frame affect the pre‐extinction palaeobiological record. We also show that the apparent high endemicity of dinosaurs in the Campanian is a result of non‐contemporaneous geological units within large time bins. This study helps to illustrate the utility of high‐resolution, regional studies to supplement our understanding of factors governing global diversity in deep time and ultimately how geology is inherently tied to our understanding of past changes in species richness.

Completeness of the known graptoloid palaeontological record

Article

Jun 2019

Using a high-resolution chronology of graptoloid first and last appearances, we apply mathematical models that allow the simultaneous inference of the probability distribution of species durations and the effective sampling rate relating those durations to the observed stratigraphic ranges. This approach allows the completeness of the documented palaeontological record of graptoloids to be assessed. We estimate that c. 75% of species in the geographical regions that contribute to the stratigraphic data have been sampled and that, of those species known from more than a single stratigraphic horizon, c. 85% of their original durations, on average, are represented by their global composite stratigraphic ranges. As expected in light of their biostratigraphic importance, graptoloids have one of the most completely documented records among groups of fossil organisms. We expect that application of the methods used herein will show comparably complete records for other biostratigraphically relevant groups. Supplementary material: The R code and data are available at https://doi.org/10.6084/m9.figshare.c.4547174

Paleozoology and Paleoenvironments: Fundamentals, Assumptions, Techniques

Book

Feb 2019

Paleozoology and Paleoenvironments outlines the reconstruction of ancient climates, floras, and habitats on the basis of animal fossil remains recovered from archaeological and paleontological sites. In addition to outlining the ecological fundamentals and analytical assumptions attending such analyzes, J. Tyler Faith and R. Lee Lyman describe and critically evaluate many of the varied analytical techniques that have been applied to paleozoological remains for the purpose of paleoenvironmental reconstruction. These techniques range from analyses based on the presence or abundance of species in a fossil assemblage to those based on taxon-free ecological characterizations. All techniques are illustrated using faunal data from archaeological or paleontological contexts. Aimed at students and professionals, this volume will serve as fundamental resource for courses in zooarchaeology, paleontology, and paleoecology.

Stratigraphy, provenance, and tectonic significance of the Punchbowl block, San Gabriel Mountains, California, USA

Article

Full-text available

Jan 2019
GEOSPHERE

The Punchbowl block is a fault-bounded crustal sliver in the eastern San Gabriel Mountains of southern California with important implications for conflicting reconstructions of the San Andreas fault system. Detailed mapping, determination of conglomerate-clast and sandstone compositions, and dating of detrital and igneous zircon of Oligocene-Miocene strata define two distinct subbasins and document initiation of extension and volcanism ca. 25-24 Ma, followed by local exhumation of the Pelona Schist, and transition from alluvial-fan to braided-fluvial deposition. Strata of the Punchbowl block correlate with those of other regions in southern California, confirming 40-50 km of dextral slip on the Punchbowl fault, and supporting reconstructions with 60-70 km of dextral slip on the San Gabriel/ Canton fault and ~240 km of dextral slip on the southern San Andreas fault. Provenance and probable correlations of Punchbowl-block strata argue against 80-110 km of dextral slip on the San Francisquito-Fenner-Clemens Well fault and limit the time interval during which such slip could have occurred. Synthesis of these findings with previous work produces paleogeographic reconstructions of the Punchbowl block and its probable correlatives through time.

Doubled helix: Sagdoidea is the overlooked sister group of Helicoidea (Mollusca: Gastropoda: Pulmonata)

Article

Full-text available

Dec 2017

We performed multi-locus, time-calibrated phylogenetic analyses of Jamaican Pleurodontidae to infer their relationships within pulmonate land snails. These analyses revealed that Sagdoidea, with about 200 species in the Caribbean Basin and neighbouring regions, is the sister group of Helicoidea with about 4700 species worldwide and that these superfamilies diverged 61-96 Ma. Morphological disparity in Sagdoidea is similar to that in Helicoidea despite its much lower species richness. Helicoidea originated in the New World and colonized the Old World 46-64 Ma. Pleurodontids and sagdids colonized Jamaica 15.0-18.4 and 12.8-16.5 Ma, respectively, consistent with geological estimates of Jamaican subaerial emergence by mid-Miocene. Allopatric convergence in shell morphologies required caution in using fossils from outside the geographic range of ingroup taxa to calibrate molecular clock estimates. Estimates of ages of clades varied by 24-55%, depending on the calibration points included. We use these results to revise Helicoidea and Sagdoidea. Pleurodontids from Jamaica and the Lesser Antilles were reciprocally monophyletic but other putative pleurodontids grouped basally in Helicoidea as Labyrinthidae (new family), or with Sagdidae. Newly recognized members of Sagdoidea are Solaropsinae and Caracolinae (Solaropsidae), Polydontinae (Sagdidae) and Zachrysiidae (new family). Pleurodontidae is restricted to two subfamilies, Pleurodontinae, in the Lesser Antilles, with Gonostomopsinae, a synonym, and Lucerninae resurrected for the Jamaican endemic genera Lucerna, Dentellaria, Thelidomus and Eurycratera. Lucerna and Dentellaria have been treated as subgenera of Pleurodonte, but rendered it paraphyletic in our analyses.

Palaeogeographic distribution and diversity of cephalopods during the Cambrian–Ordovician transition

Article

Full-text available

Aug 2018
Palaeoworld

Since the early 20th Century, when the first cephalopods from late Cambrian strata were discovered in North China, more than 160 species belonging to 39 genera in nine families and five orders, have been described from both North and South China, together with North America, Siberia and Kazakhstan. We compiled and analysed all published Cambrian cephalopod occurrences in these regions: the results show that the oldest undisputed cephalopods are from the Jiangshanian Stage of North China. After their origination, cephalopods reached their first diversity peak in the late Cambrian Acaroceras–Sinoeremoceras Biozone (early Stage 10). This initial diversity peak was followed by the “late Trempealeauan Eclipse”, which eradicated nearly 95% of late Cambrian genera. The extinction event coincides with similar extinctions of trilobites and some other groups of marine life. The rapid subsequent diversification of cephalopods during the Tremadocian (Early Ordovician) was paralleled by a diversification of graptoloids and radiolarians. © 2018 Elsevier Ireland Ltd Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS

Regional impacts of global climate change: A local humid phase in central Iberia in a late Miocene drying world

Article

Jul 2018

Locomotor diversity within past and present guilds of large predatory mammals

Article

Full-text available

Jan 1985

Blaire Van Valkenburgh

The impact of environment, interspecific competition, and, to a lesser extent history, on the structure of the guild of large predatory mammals is explored in one fossil and four Recent communities. Two aspects are emphasized: (1) the number of species within each guild and (2) the extent of locomotor convergence as inferred from morphology among the constituent species. Locomotor behavior reflects habitat choice, hunting mode, and escape strategy, all of which appear to be important avenues of adaptive divergence among coexisting predators. Locomotor behavior in extinct and extant predators is determined from body weight and five measured characteristics of the postcranial skeleton, including ungual shape, elbow shape, and limb proportions. Results indicate that levels of morphologic and inferred ecologic similarity between large predators are higher in the tropical grassland guild of East Africa than in the equivalent guilds of either tropical or temperate forest. This may be due to the great density and diversity of terrestrial herbivores in the productive grasslands. The fossil guild, from the Late Chadron–Orellan (Oligocene) of North America, appears most similar to the tropical forest guilds, but the predators seem to have been slower and more robust than their modern counterparts. Since the Orellan represents an early stage in the evolution of large, fissiped carnivores, both ancestry and time could have influenced Orellan guild structure.

A likelihood approach for evaluating estimates of phylogenetic relationships among fossil taxa

Article

Full-text available

Sep 1998
PALEOBIOLOGY

Peter Wagner

Estimates of phylogenetic relationships among fossil taxa implicitly provide hypotheses about the quality of the fossil record. Phylogenetic inferences also provide hypotheses about character evolution. The likelihood of any hypothesis that makes predictions about two data sets is simply the likelihood of the hypothesis given the first data set times the likelihood of the same hypothesis given the second data set. In this case, data set 1 represents stratigraphy and data set 2 represents morphology. Statistical methods exist for determining the likelihood of hypothesized levels of sampling. The likelihood of a hypothesized amount of character change yielding a particular most-parsimonious solution (i.e, L[hypothesized length | parsimony length] can be evaluated with simulations. A reanalysis of hyaenid phylogeny based on published character and stratigraphic data is presented here, using the maximum likelihood method. Two trees are found, depending on assumptions about ambiguous species, which are 11 and 10 steps longer than the most parsimonious tree (61 or 60 vs. 50 steps). However, the trees invoke far less stratigraphic debt (9 or 12 units vs. 47 units as measured in Mammal Zones). An important feature of the results is that the most likely tree length given hyaenid character data is estimated to be 56 to 62 steps (depending on the model of character evolution) rather than 50 steps. The likelihood tree suggests stronger trends toward bone-crushing specializations than does the parsimony tree and further suggests that high levels of homoplasy caused parsimony to underestimate the true extent of those trends. Simulations based on the character data and fossil record of hyaenids suggest that the maximum likelihood method is better able to estimate correct trees than is parsimony and somewhat better able to do so than previously proposed phylogenetic methods incorporating stratigraphy.

Diachrony of mammalian appearance events: Implications for biochronology: Comments and Reply

Article

Full-text available

Oct 1998
GEOLOGY

New species of Batodonoides (Lipotyphla, Geolabididae) from the early Eocene of Wyoming: smallest known mammal? Journal of Mammalogy

Article

Full-text available

Aug 1998

A new early Eocene insectivore, Batodonoides vanhouteni, sp. nov., has molar teeth indicating a body size smaller than that of any mammal known to date. B. vanhouteni is the oldest known species assigned to the genus, which was known previously from the middle Eocene of California. The type, all associated maxilla and mandible, preserves P2-M2 and c1-p2, dp4, p4-m3, with alveoli for i1-3. Some teeth (P4, c1, and p4) are still erupting, indicating that the specimen is a juvenile at about the age of dispersal. B. vanhouteni had two sets of functional teeth, unlike extant mammals of very small size. it retains the primitive pattern of cheek-tooth replacement, erupting P3 before P4, unlike the P4-before-P3 sequence of almost all Lipotyphla. The distribution of body masses for Clarkforkian and Wasatchian insectivores indicates that late Paleocene and early Eocene lipotyphlans occupied a lower range of body masses (ca. 1.3-53 g) compared to extant Lipotyphla (ca. 2.5-1,100 g); the upper range of insectivore body masses was occupied by now-extinct "Proteutheria."

Portrait of a Late Paleocene (Early Clarkforkian) Terrestrial Ecosystem: Big Multi Quarry and Associated Strata, Washakie Basin, Southwestern Wyoming

Article

Full-text available

Dec 1998

In-depth understanding of past climatic and biotic change requires the study of ancient ecosystems. However, terrestrial plants and vertebrates are preferentially preserved under very different taphonomic conditions, and diverse fossil floras and faunas are rarely found in close association. Big Multi Quarry and associated strata in the uppermost Fort Union Formation of the Washakie Basin, southwestern Wyoming, provide a uniquely detailed record of terrestrial fauna, flora, and climate during the early Clarkforkian. The Clarkforkian Land Mammal Age, approximately the last million years of the Paleocene, wars an interval of global warming that had profound biotic consequences. The mammalian fauna of Big Multi Quarry, consisting of 41 species, is the most diverse known from a single Clarkforkian locality. Unlike most other Clarkforkian faunas, this assemblage is not significantly biased against small forms. Lipotyphlan insectivores were dominant, and arboreally adapted taxa were abundant and diverse. The closely associated and well-preserved fossil plant assemblage was overwhelmingly dominated by a single species belonging to the birch family. Floral richness, heterogeneity, and evenness were as low as in the Tiffanian of the same region, showing that forest structure remained monotonous even as climate warned and mammals diversified in the Clarkforkian. The plant assemblage more closely resembles middle than early Clarkforkian floras of northern Wyoming, suggesting northward migration, of the ranges of plant taxa coincident with warming. A great deal of research has focused on the unusually warm interiors of continents in the terminal Paleocene and early Eocene. Multiple lines of evidence from our study, including sedimentological indicators, analyses of the nearest living relatives and functional analogues of the fossil plants and animals, size and margin analysis of fossil leaves, and cenogram analysis of the mammalian fauna, indicate that southwestern Wyoming had a humid subtropical climate with little or no seasonal frost or marked dry season, well before the terminal Paleocene.

Mammals of the Rio Jurua and the evolutionnary and ecological diversification of Amazonia

Article

Full-text available

Jan 2000

Les communantés de mammifères du Paléogène (Eocène supérior et Oligocène) d'Europe Occidentale: structures, milieux et évolution

Thesis

Full-text available

Mar 1988

Serge Legendre

Published in: Münchner Geowissenschaftliche Abhandlungen, Reihe A, 116: 1-110 (1989) https://www.researchgate.net/publication/233944351_Les_communauts_de_mammifres_du_Palogne_%28Eocne_suprieur_et_Oligocne%29_d%27Europe_occidentale_structures_milieux_et_volution_Mammalian_communities_from_the_Paleogene_%28late_Eocene_and_Oligocene%29_of_western_Europe_structures_environments_and_evolution?ev=prf_pub

Mammals of the Rio Juruá and the evolutionary diversification of Amazonia

Article

Full-text available

Sep 2009

Nesse estudo descreve-se a fauna de mamíferos não-voadores do Rio Juruá, situado a oeste da Amazônia brasileira, por meio das coletas realizadas ao longo desse rio durante levantamento de aproximadamente um ano. Os trabalhos de campo foram planejados para examinar os efeitos do rio na estrutura dos vertebrados terrestres, inclusive dos mamíferos, tanto no que se refere às comunidades quanto aos padrões de diferenciação geográfica para espécies individuais. Dezesseis sítios de coleta primários foram inventariados segundo desenho experimental constituido por dois pares de sítios situados em margens opostas, em cada uma das quatro regiões distribuidas das proximidades da foz até a região da cabeceira do rio. Um total de 81 espécies foram obtidas, e inclui nove espécies novas para a ciência. Quarto delas estão descritas neste estudo; as outras encontram-se descritas em outros trabalhos. A estrutura das comunidades foi determinada a partir de um protocolo de amostragem padronizado para cada um dos 16 sítios que incluia estações de captura, com armadilhas terrestres e arbóreas, nas matas de várzea e de terra firme. Capturas adicionais foram realizadas em habitats considerados secundários em todos os sítios de amostragem. Descrevem-se esses sítios, o esforço de amostragem e a localização das estações de captura correspondentes aos habitats locais. Também descreve-se cada uma das espécies de marsupiais e de roedores murídeos e equimídeos encontradas, comenta-se sobre sua sistemática, e sumarizam-se aspectos relativos ao uso de habitat, história natural, distribuição geográfica, e diferenciação geográfica baseada em caracteres morfológicos e moleculares. A variação nas sequências do gene mitocondrial citocromo-b foi examinada para amostras de 41 das 45 espécies de marsupiais e roedores obtidas. Para cada um dos táxons, cujas amostras eram suficientes, examinaram-se os padrões de diferenciação na bacia do Rio Juruá, e discutiram-se esses padrões para toda a Amazônia e, em alguns casos, incluiu-se também a Mata Atlântica. Posteriormente, examinaram-se os padrões de organização das comunidades na bacia do Rio Juruá e em toda a Amazônia, chamando atenção sobre a distribuição geográfica do que aparentemente representam unidades faunística maiores, independentes das diferenças no habitat. Retorna-se, então, ao objetivo original e utilizam-se os princípios filogeográficos para analisar os padrões geográficos de diferenciação entre os mamíferos não-voadores com referência à Hipótese dos Rios. Mostra-se que embora para alguns táxons o Rio Juruá funcione como barreira, a maioria dos táxons ou é largamente indiferenciada em toda a bacia ou marcadamente dividida em clades de haplotipos monofiléticos separáveis em duas unidades distintas, uma rio-acima e outra rio-abaixo. Argumenta-se que essa concordância na localização geográfica dos limites dos clados indicam uma história comum e, tanto a idade desses clados quanto suas posições geográficas em relação às estruturas geológicas subjacentes sugerem que a evolução das paisagens tem sido um componente importante, embora desconsiderado dos processos de diversificação no oeste da Amazônia.

Mammalian community response to the latest Paleocene thermal maximum: An isotaphonomic study in the northern Bighorn Basin, Wyoming

Article

Full-text available

Nov 1998
GEOLOGY

New stratigraphic and paleontological information from the McCullough Peaks, northern Bighorn Basin, Wyoming, is incorporated into an isotaphonomic faunal database and used to investigate the impact of the latest Paleocene thermal maximum and coincident earliest Wasatchian immigration event on local mammalian community structure. Surface collections from Willwood Formation overbank deposits provide taphonomically consistent and stratigraphically resolved samples of the medium- to large-sized components of underlying mammalian communities. Rarefaction shows that the immigration event caused an abrupt and dramatic increase in species richness and evenness. After this initial increase, diversity tapered off to more typical Wasatchian levels that were still higher than those in the preceding Clarkforkian. Wasatchian immigrants were rapidly incorporated into the new community organization, representing ˜20% of the taxa and ˜50% of the individuals. Immigrant taxa generally had larger body sizes and more herbivorous and frugivorous dietary habits compared to endemic taxa, causing significant turnover in body-size structure and trophic structure. There was a significant short-term body-size decrease in many lineages that may have been prompted by the elevated temperatures and/or decreased latitudinal thermal gradients during the latest Paleocene thermal maximum. Rapid short-term climatic change (transient climates) and associated biotic dispersal can have abrupt and long-lasting effects on mammalian community evolution.

Article

Full-text available

Jan 1985

The number of species in a community is one of the most commonly used measures of diversity. This measure is, however, affected by sample size. The rarefaction method attempts to correct sample size bias by assuming an underlying sampling model. Several rarefaction models are shown to be similar analytically. This similarity holds not only for the expected number of species but also for the variance of the number of species.

Plant and mammal diversity in the Paleocene to Early Eocene of the Bighorn Basin

Article

Full-text available

May 1995
PALAEOGEOGR PALAEOCL

Abundant plant and vertebrate fossils have been recovered from fluvial sediments deposited in the Bighorn Basin, Wyoming, during the first 13 m.y. of the Tertiary. Here we outline and discuss changes in the composition and diversity of floras and faunas during this period, which includes the recovery of terrestrial ecosystems from the K/T boundary extinctions, and later, during the Paleocene-Eocene transition, the greatest global warming of the Cenozoic.Floral diversity has been studied at three levels of spatial resolution: sub-local (at individual collecting sites), local (along a single bed or stratigraphic horizon), and basin-wide (regional). Sub-local diversity shows a moderate increase from the early to late Paleocene, followed by a decrease across the Paleocene/Eocene boundary, then an increase into the later early Eocene. Local heterogeneity was lower in Paleocene backswamp floras, although distinct groups of species dominated in different local fluvial settings such as backswamps and alluvial ridges. Heterogeneity of backswamp forests increased by about 65% from the early to late Wasatchian (early Eocene). The number of plant species inferred from the Bighorn Basin dataset rose gradually from the Puercan to an early Clarkforkian peak of about 40 species, declined sharply to about 25 species by the Clarkforkian/Wasatchian boundary, then rose through the Wasatchian to about 50 species.A regional analysis of mammalian genera shows high turnover and a rapidly increasing number of genera within a million years of the K/T boundary (10–50 genera), a slight decline to 40 genera by the early Clarkforkian, then an increase from 40 to 75 genera by the late Wasatchian.Our analyses found no major extinctions in mammals during the Paleocene and early Eocene in the Bighorn Basin, but a one-third decrease in the number of plant species at about the Paleocene/Eocene boundary. Rates of taxonomic turnover were much higher for mammals than plants. The diversity trends for plants and mammals show little congruence, implying that the two groups responded in a very different manner to post K/T extinction opportunities. There is also little congruence between plant diversity levels and change in mean annual temperature (MAT) as inferred from foliar physiognomy.

The reciprocal interaction of angiosperm evolution and tetrapod herbivory

Article

Full-text available

Feb 1987
REV PALAEOBOT PALYNO

We have interpreted the history of angiosperm-herbivorous tetrapod interactions based on the fossil record of the two groups. This history can be divided conveniently into four stages. Stage 1, lasting ∼ 40 Ma (Barremian-Campanian), was characterized by diverse large herbivores, few species of small herbivores, and r-selected angiosperms. The dominant interaction between herbivores and angiosperms during this stage was generalized herbivory. During Stage 2 (∼ 10 Ma, Campanian - Maestrichtian), small herbivores increased in diversity; larger angiosperms and larger angiosperm diaspores became more common. Generalized herbivory was still the dominant interaction in this stage, but frugivory/dispersal of angiosperm diaspores by small herbivores became more important. In Stage 3 (∼ 25 Ma, Paleocene - mid-Eocene) large angiosperms and large angiosperm diaspores were diverse; large herbivores were initially absent, later low in diversity. Frugivory/dispersal was common during this stage, generalized herbivory much less so. During Stage 4 (∼ 30 Ma, Oligocene - Recent), the relative importance of large vs. small herbivores and large vs. small angiosperms has varied by community, as has the relative importance of generalized herbivory vs. frugivory/dispersal.

Phylogeny estimation and hypothesis using Maximum Likelihood. Ann. Rev. Ecol. Syst. 28:437-466

Article

Full-text available

Nov 1997
Annu Rev Ecol Systemat

One of the strengths of the maximum likelihood method of phylogenetic estima- tion is the ease with which hypotheses can be formulated and tested. Maximum likelihood analysis of DNA and amino acid sequence data has been made practi- cal with recent advances in models of DNA substitution, computer programs, and computational speed. Here, we describe the maximum likelihood method and the recent improvements in models of substitution. We also describe how likelihood ratio tests of a variety of biological hypotheses can be formulated and tested using computer simulation to generate the null distribution of the likelihood ratio test statistic.

A kinetic model of Phanerozoic taxonomic diversity. I. Analysis of marine orders

Article

Jan 1978
PALEOBIOLOGY

J.J. Jr Sepkoski

A simple equilibrial model for the growth and maintenance of Phanerozoic global marine taxonomie diversity can be constructed from considerations of the behavior of origination and extinction rates with respect to diversity. An initial postulate that total rate of diversification is proportional to number of taxa extant leads to an exponential model for early phases of diversification. This model appears to describe adequately the “explosive” diversification of known metazoan orders across the Precambrian-Cambrian Boundary, suggesting that no special event, other than the initial appearance of Metazoa, is necessary to explain this phenomenon. As numbers of taxa increase, the rate of diversification should become “diversity dependent.” Ecological factors should cause the per taxon rate of origination to decline and the per taxon rate of extinction to increase. If these relationships are modeled as simple linear functions, a logistic description of the behavior of taxonomie diversity through time results. This model appears remarkably consistent with the known pattern of Phanerozoic marine ordinal diversity as a whole. Analysis of observed rates of ordinal origination also indicates these are to a large extent diversity dependent; however, diversity dependence is not immediately evident in rates of ordinal extinction. Possible explanations for this pattern are derived from considerations of the size of higher taxa and from simulations of their diversification. These suggest that both the standing diversity and the pattern of origination of orders may adequately reflect the behavior of species diversity through time; however, correspondence between rates of ordinal and species extinction may deteriorate with progressive loss of information resulting from incomplete sampling of the fossil record.

Dynamics of taxonomic diversity

Article

Sep 1980

A general model of taxonomic diversity, incorporating diversity-dependent rates of origination and extinction, is constructed to examine the dynamic responses of diversity to perturbation. The model predicts that the trajectories of diversification increase and decrease are substantially different. The trajectories of diversity during disequilibrium conditions are displayed in phase diagrams to permit a simple graphical analysis of stability. A positive displacement of diversity from equilibrium results in a rapid decline in diversity and may involve an initial overshoot of the equilibrium condition. A negative displacement of equal magnitude results in a gradual increase in diversity. The model is expressed as a nonlinear difference equation to incorporate intrinsically a delay time due to the characteristic noninstantaneous response of origination and extinction. The model initially assumes a parabolic curve expressing total taxon origination rate as a function of diversity. A second model, constructed assuming a sigmoidal total taxon origination rate derived from considerations of allopatric speciation, enhances the asymmetry of the diversity response. The delayed recovery of the Triassic fauna is shown to be characteristic of return to equilibrium from an undersaturated condition, whereas the more rapid “catastrophic” decline in the Late Permian fauna is shown to be characteristic of return to equilibrium from the oversaturated condition. It is proposed, although not assumed, that perturbation may include a degree of selectivity related to the dispersal abilities of organisms, thereby enhancing the observed asymmetry.

Rarefaction and rarefiction—the use and abuse of a method in paleoecology

Article

Jan 1979
PALEOBIOLOGY

John C. Tipper

Rarefaction is a method for comparing community diversities that has consistently been abused by paleoecologists: here its assumptions are clarified and advice given on its application. Rarefaction should be restricted to comparison of collections from communities that are taxonomically similar and from similar habitats: the collections should have been obtained by using standardised procedures. The rarefaction curve is a graph of the estimated species richness of sub-samples drawn from a collection, plotted against the size of sub-sample: it is a deterministic transform of the collection's species-abundance distribution. Although rarefaction curves can be compared statistically, it may be more efficient to compare the species-abundance distributions directly. Both types of comparison are discussed in detail.

Probabilities of origination, persistence, and extinction of families of marine invertebrate life

Article

Jan 1991

In this paper we model the process of taxonomic evolution as a Galton-Watson branching process in discrete time and, using maximum likelihood, develop methods to estimate the probabilities of origination, persistence, and extinction of fossil taxa. We use the methods to estimate the probabilities of origination, persistence, and extinction of families (1) within 135 orders of marine invertebrate organisms, (2) within 12 phyla, and (3) within all marine invertebrate life (independently of the suprafamilial classification). Most orders, including the arcoid bivalves, the dentaloid scaphopods, the orders of chitins, and many others, have relatively low probabilities of familial origination and extinction. The various ammonoid and trilobite orders, and some others, have high probabilities of origination and extinction. Among the phyla, the Archaeocyatha have the highest probabilities of familial origination and extinction, and the Annelida the lowest, with the more typical phyla of shelly organisms clustering near the high end of the probability scale. The Porifera and Protozoa also have low probabilities but not as low as the Annelida. The estimated origination and extinction probabilities for families within all marine invertebrate life are 0.470 and 0.452 per stage, respectively, values that are at the high end of the probability scale. We have also estimated the probabilities of ultimate extinction (extinction of all families) of the supertaxa. By analyzing the changes of the diversity during each stratigraphic stage separately, we have also determined the trajectories of the estimated origination and extinction probabilities for families within all marine invertebrate life. The estimated origination probability is relatively high in association with the expansion of the Cambrian and Paleozoic evolutionary faunas and declines to more normal levels for the remainder of the Phanerozoic. The trajectory of the estimated extinction probability is from nearly zero early in the Phanerozoic to more normal levels later, showing clearly defined peaks in association with the five Phanerozoic mass-extinction events. The terminal Cretaceous mass extinction is the only one of the five that was not preceded by a monotonic decline of origination probability or by a series of stages with low origination probability. It appears to have been a unique, singular event. Because the mathematical theory we employ as a model corresponds so closely to the processes of taxonomic evolution as we understand them, we believe that the theory provides a reasonable model of biological reality.

Diversity-dependent species dynamics: incorporating the effects of population-level processes on species dynamics

Article

Jan 1989

Brian A. Maurer

A general model of species dynamics must incorporate the effects of species number on the processes of speciation and extinction. Previous models make specific assumptions about these effects, but do not consider the effects of dynamics of lower level entities on speciation and extinction rates. A hierarchical model is developed which explicitly describes the effects of energy use by species on speciation and extinction rates. Empirical analysis of a data set on the diversification of fossil Miocene horses suggests that the logistic and hierarchical models have similar descriptive power. The hierarchical model incorporates insights from recent considerations of the nature of a hierarchical theory of biology. Further progress in developing such a theory will depend on the success with which relationships among levels in the biological hierarchy are able to be defined. -Author

Morphologic patterns of diversification: examples from trilobites

Article

Jan 1991

M. Foote

The morphologic diversification of the Trilobita is investigated using a Fourier description of the cranidia of Cambrian and Ordovician trilobites from North America. Morphologic diversity increases from the Early Cambrian to the Middle Ordovician, but does not correlate well with patterns of generic or familial diversity. Suprageneric taxa of trilobites are shown objectively to represent morphotypes. Morphologic dispersion among suprageneric taxa and the distinctness of these taxa both increase from the Cambrian to the Ordovician. The origination of higher taxa may be linked to the opening of new adaptive zones, particularly in the Early Ordovician, following widespread extinctions of trilobites. -from Author

Crocodilian diversity in space and time: The role of climate in paleoecology and its implication for understanding K/T extinctions

Article

Sep 1998
PALEOBIOLOGY

Paul J. Markwick

The taxonomic diversity of crocodilians (Crocodylia) through the last 100 million years shows a general decline in the number of genera and species to the present day. But this masks a more complex pattern. This is investigated here using a comprehensive database of fossil crocodilians that provides the opportunity to examine spatial and temporal trends, the influence of sampling, and the role of climate in regulating biodiversity. Crown-group crocodilians, comprising the extant families Alligatoridae, Crocodylidae, and Gavialidae, show the following trend: an initial exponential diversification through the Late Cretaceous and Paleocene that is restricted to the Northern Hemisphere until after the K/T boundary; relatively constant diversity from the Paleocene into the middle Eocene that may be an artifact of sampling, which might mask an actual decline in numbers; low diversity during the late Eocene and Oligocene; a second exponential diversification during the Miocene and leveling off in the late Miocene and Pliocene; and a precipitous drop in the Pleistocene and Recent. The coincidence of drops in diversity with global cooling is suggestive of a causal link—during the initial glaciation of Antarctica in the Eocene and Oligocene and the Northern Hemisphere glaciation at the end of the Pliocene. However, matters are complicated in the Northern Hemisphere by the climatic effects of regional uplift. Although the global trend of diversification is unperturbed at the K/T boundary, this is largely due to the exceptionally high rate of origination in the early Paleocene. Nonetheless, the survival of such a demonstrably climate-sensitive group strongly suggests that a climatic explanation for the K/T mass extinctions, especially the demise of the dinosaurs, must be reconsidered.

Patterns of species abundance and diversity, Ecology and Evolution of Communities

Article

Jan 1975

R.M. May

Size variability of the teeth in living mammals and the diagnosis of closely related sympatric fossil species

Article

Jan 1974

Philip D. Gingerich

Land mammal high-resolution geochronology, intercontinental overland dispersals, sea level, climate, and vicariance

Chapter

Jan 1995

The generally well developed and understood stratigraphic record associated with fossil mammals in North America is combined with independent chronological data sets that foster the development of high-resolution geochronology in nonmarine sequences. An updated chronology for all North American mammal ages (or subdivisions) is utilized to examine the tempo and mode of overland mammal immigration/emigration episodes during the Cenozoic Era. In addition to the 30 or more "background' dispersals involving only a few taxa, ten major immigration/emigration episodes are recorded during the Cenozoic Era in North America. All are important for evaluating the dispersal pattern, as well as for mammal age boundary definition. In certain intervals, apparently lowered sea level had no effect on dispersal, but in an even larger number of cases immigration took place in spite of what appears to have been times of relative sea-level highstand. Thus tectonic, climatic, and other factors must be considered to account for North America's dispersal history during the Cenozoic Era. -from Authors

Implications of Continental Drift to the Earth Sciences

Article

Oct 1974

Quantitative geophysical evidence for the reality of continental drift was first obtained from the comparison of palaeomagnetic directions in igneous and sedimentary rocks from different continents. More recently Wegeners concept of continental drift has been beautifully complimented by the hypothesis of sea-floor spreading. Again the palaeomagnetism of the ocean floor has provided quantitative evidence for its occurrence. Thus the older qualitative arguments from the geological record, presented so imaginatively by Alfred Wegener, have been vindicated. In recent years we have seen a marked change in the climate of scientific opinion about the reality of major horizontal movements of parts of the Earths surface and, from palaeomagnetic and other geophysical studies, the positions of the continents in different geological periods and the evolution of the ocean basins are being determined. It is still not very clear how these movements take place in time and there is still considerable uncertainty about the precise relationships of different parts of the Earth's surface during the geological past. These developments have, however, essentially ended the long debate about whether or not the classical lines of geological evidence, palaeoclimatic, palaeontological distributions, global tectonic patterns and lithological relationships, support or refute drift. What is now scientifically significant is the study of the geological record in the light of the known horizontal displacements. This is of great potential importance to various other sciences involved in the study of our environment, e.g. biology, global meteorology. These two volumes are the proceedings of the April 1972 NATO Advanced Study Institute held in the University of Newcastle upon Tyne. They commence mainly with reviews of the objective evidence for the past position of the continents, i.e. the palaeomagnetism of continental and oceanic rocks. The palaeontological evidence is then examined to see how the creation of supercontinents and their fragmentation affects the mobility and rate of evolution of the biota on and around them. This data must also be examined carefully in order to delineate evidence which still appears inconsistent with current views of the past distribution of the continents to see if our presentviews need modification or whether such discrepancies can yield further information about our planet in the past, for example, the distribution of topographic, predatory or climatic barriers to the migration of terrestrial fauna. Similarly, the movement of continental fragments into different climatic belts obviously has an effect on their prevailing climate, but this movement, particularly the formation or fragmentation of supercontinents, must also hope a drastic effect on the climatic belts themselves.

On Calculating Birth and Death Rates

Article

Mar 1997

Bertram G. Murray

Implications of Continental Drift to the Earth Sciences.

Article

Dec 1975
Syst Zool

The Ecological Detective: Confronting Models With Data

Book

Jan 1997
Monogr Popul Biol

Body Size in Mammalian Paleobiology: Estimation and Biological Implications

Article

Dec 1993
Geobios

Marguerite Hugueney

Origination and extinction components of taxonomic diversity: Paleozoic and post-Paleozoic dynamics

Article

Dec 2000
PALEOBIOLOGY

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.

Equilibrium Models of Evolutionary Species Diversity and the Number of Empty Niches

Article

Dec 1984

To quantify the 'emptiness' of adaptive space a mathematical model of diversification is derived which makes explicit the relationship between maximum species capacity and realized diversity. The proportion of niches empty at equilibrium is a function only of the intrinsic rates of species origination and extinction. Estimates of these rates for 8 marine invertebrate groups suggest that the mean proportion of empty niches is somewhere in the range of 12-54%. Evolution in such an open adaptive space should be characterized by unremitting taxonomic turnover and continuous faunal change (but only occasional adaptive improvements), and should permit the rapid establishment of new morphospecies. These expectations are qualitatively borne out by the fossil record. -from Authors

Body size in mammalian paleobiology: Estimation and biological implications

Article

Oct 1993

Matthew J. Ravosa

Patterns of diversity, extinction and origination in the Ordovician-Devonian Stropheodontacea

Article

Jun 1996

Charles W. Harper Jr

Evolutionary patterns exhibited by ninety‐one genera and subgenera of Ordovician‐Devonian Stropheodontacea can be inferred using two measures of standing diversity, along with raw diversity, and three measures each of extinction rates, origination rates and turnover rates. Of the three measures defined for each type of rate, one counts taxa that are confined to the interval and two do not. Of the latter, one is defined on a pertotal taxa and one on a per‐standing‐diversity basis.If it is assumed that the available data adequately represents the total range of morphological diversity and time distribution of the Stropheodontacea, then these measures can be treated as descriptive statistics and several patterns emerge: Diversity increases monotonically from Caradoc to Emsian and then decreases from Emsian to zero in the Famennian. Extinction rates increase from Wenlock to Frasnian. Origination rates show three to four peaks. Turnover rates show a decrease in the Early Silurian, a local peak in the Wenlock, and an increase from Pridoli to Frasnian.Alternatively, if the observed data is treated as a sample of a larger population then 80% and 95% confidence limits indicate that several of the patterns (mostly involving Silurian intervals) are not statistically significant. Any assessment of the effect of errors on extinction rates should address false positives (taxa falsely regarded as becoming extinct in a time interval) not just false negatives (taxa falsely regarded as not becoming extinct in the interval). One way to evaluate error: assess likely ranges of reliability (measured as proportions of true positives and true negatives), sample sizes, and the true proportion of taxa that become extinct in an interval. Estimate the probability that 80% (95%) confidence limits on extinction rates contain the true proportion; if the probability is low then view any alleged patterns with skepticism. The stropheodontacean dataset passes this test.

Notes on the Species-Area Curve

Article

Jan 1963

K. Shinozaki

Evolutionary pulsations: Evidence from Phanerozoic diversity patterns

Article

Jan 1973

Conjuction among taxonomic distributions and the Miocene mammalian biochronology of the Great Plains

Article

Jan 1992

John Alroy

This paper presents a new means of interpreting the distribution of taxa among taxonomic lists. Traditionally, "similarity' indices have been used to compare lists, and "association' measures have been used to compare taxonomic distributions. It is argued that when sampling regimes are poorly understood, all similarity and association indices are unjustifiable. However, observations that taxa have overlapping or nonoverlapping distributions are universally meaningful. Because greater sampling can only increase the number of known conjunctions and because long lists serve as conjunctional Rosetta Stones, conjunction data sets can be far more reliable than the lists that generate them. The method is used to analyze a set of 271 Miocene large-mammal genus lists from the Great Plains region. -from Author

Classification of Mammals Above Species Level

Article

Jan 1997

Appearance event ordination: a new biochro-nological method

Article

Jan 1994

John Alroy

The fundamental goal of biochronology is ordering taxonomic first and last appearance events. The most useful biochronologic data are of the form "the first appearance event of one taxon predates the last appearance event of a second taxon' (FAE<LAE). FAE<LAE data accurately synthesize two disparate sources of information: routine biostratigraphic observations and taxonomic lists that may have no stratigraphic context. Appearance event ordination, the new method introduced here. is intended to summarize FAE<LAE data. The algorithm is founded on the following parsimony criterion: arrangements of FAEs and LAEs should always imply FAEi<LAEj when this is known, and otherwise imply LAEj<FAEi whenever possible. An analysis of the Plio-Pleistocene mammalian record in the Lake Turkana region is used to illustrate the method. -from Author

Raup DM. Geometric analysis of shell coiling: general problems. J Paleontol 40: 1178-1190

Article

Nov 1965

D. M. Raup

Temporal variation in extinction risk and temporal scaling of extinction metrics

Article

Jan 1994

Mike Foote

Many areas of paleobiological research require reliable extinction metrics. Branching-and-extinction simulations and data on Phanerozoic marine families and genera are used to investigate the relationship between interval length and commonly used extinction metrics. Normalization of extinction metrics for interval length is problematic, even when interval length is known without error, because normalization implicitly assumes some model of variation in extinction risk within an interval. If extinction risk within an interval were constant, or if it varied but played no role in the definition of stratigraphic intervals, then Van Valen's time-normalized extinction metric would provide a measure of average extinction risk that is effectively unbiased by interval length. When extinction risk varies greatly within an interval and interval boundaries are drawn at times of heavy extinction, extinction metrics that normalize for interval length are negatively correlated with interval length. Despite its intuitive appeal, the per-taxon extinction rate (proportional extinction per million years) is biased by interval length under a wide range of extinction models. Empirically, time-normalized extinction metrics for Phanerozoic families and genera are negatively correlated with interval length. This is consistent with an extinction model in which many times of very low risk are punctuated by a few times of very high risk which in turn determine stage boundaries. Origination and extinction patterns are similar, but origination intensity varies less among stages than extinction intensity. This observation has at least two plausible explanations: that origination episodes are more protracted than extinction episodes, and that biologic groups do not respond in unison to origination opportunities the way they seem to respond during extinction events. For families and genera, there is enough variation in extinction intensity among stages that stage length can be ignored when studying certain extinction patterns over the entire Phanerozoic.

Use of Cenograms in mammalian paleoecology. A critical review.

Article

Dec 1999
Lethaia

Jesús Rodríguez

Cenograms are graphic representations of the size distribution of the mammalian species present in a community and are used in palaeoecological studies to obtain information about the environment. Three empirical rules are commonly applied in the interpretation of cenograms. This paper reviews the methodology of cenograms, special attention being paid to those rules. A database of 92 recent faunas and environmental data has been used to explore the relationships between the shape of the cenograms and the environment. A quantitative procedure has been developed to test the validity of the rules from a statistical point of view. The analyses carried out in this paper failed to confirm the alleged relationships between the size distribution of the large mammals and the aridity of the environment and between the size distribution of the small mammals and the temperature. The gap in medium-sized species is related to the vegetation structure, although only in tropical communities.

Global climate change and North American mammalian evolution

Article

Jan 2000

Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit organization founded in 1995 to build trusted digital archives for scholarship. We work with the scholarly community to preserve their work and the materials they rely upon, and to build a common research platform that promotes the discovery and use of these resources. For more information about JSTOR, please contact support@jstor.org. Abstract. -We compare refined data sets for Atlantic benthic foraminiferal oxygen isotope ratios and for North American mammalian diversity, faunal turnover, and body mass distributions. Each data set spans the late Paleocene through Pleistocene and has temporal resolution of 1.0 m.y.; the mammal data are restricted to western North America. We use the isotope data to compute five separate time series: oxygen isotope ratios at the midpoint of each 1.0-m.y. bin; changes in these ratios across bins; absolute values of these changes (= isotopic volatility); standard deviations of multiple isotope measurements within each bin; and standard deviations that have been detrended and corrected for serial correlation. For the mammals, we compute 12 different variables: standing diversity at the start of each bin; per-lineage origination and extinction rates; total turnover; net diversification; the absolute value of net diversification (= diversification volatility); change in pro-portional representation of major orders, as measured by a simple index and by a G-statistic; and the mean, standard deviation, skewness, and kurtosis of body mass. Simple and liberal statistical analyses fail to show any consistent relationship between any two isotope and mammalian time series, other than some unavoidable correlations between a few untransformed, highly autocor-related time series like the raw isotope and mean body mass curves. Standard methods of detrend-ing and differencing remove these correlations. Some of the major climate shifts indicated by ox-ygen isotope records do correspond to major ecological and evolutionary transitions in the mam-malian biota, but the nature of these correspondences is unpredictable, and several other such tran-sitions occur at times of relatively little global climate change. We conclude that given currently available climate records, we cannot show that the impact of climate change on the broad patterns of mammalian evolution involves linear forcings; instead, we see only the relatively unpredictable effects of a few major events. Over the scale of the whole Cenozoic, intrinsic, biotic factors like logistic diversity dynamics and within-lineage evolutionary trends seem to be far more important.

Janis, C. M. and P. B. Wilhelm. Were there mammalian pursuit predators in the Tertiary? Dances with wolf avatars. Journal of Mammalian Evolution

Article

Jun 1993

Fast-running, long-legged pursuit carnivores are familiar members of the present-day ecosystem, and it has been assumed that extinct large predators took similar ecomorphological roles (i.e., were wolf avatars) in past faunas. While these fossil taxa may also have been meat-specialists, we present evidence from limb morphology to show that there was no modern type of pursuit predator until the latest Tertiary. In contrast, ungulates evolved longer legs similar to those of present-day cursorial taxa by the middle Tertiary, some 20 million years earlier. These data suggest the need for the reevaluation of many classical evolutionary stories, not only about assignation of fossil taxa to a wolf-like mode of predatory behavior, but also to issues such as the coevolution of long legs and fast running speeds between predator and prey, and even the implicit assumption that cursorial morphologies are primarily an adaptation for speed. We conclude that evolutionary change in ungulate limb morphologies represents an adaptation to decrease transport costs in association with Tertiary climatic changes and that the present-day predation mode of long distance pursuit is a Plio-Pleistocene phenomenon, related to the development of colder and more arid climates.

Constant extinction, constrained diversification, and uncoordinated stasis in North American Mammals

Article

Dec 1996
PALAEOGEOGR PALAEOCL

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.

The RASC method for ranking and scaling of biostratigraphic events

Article

May 1999
EARTH-SCI REV

The RASC method for ranking and scaling of biostratigraphic events was developed by the authors and associates during the past 20 years. The purpose of ranking is to create an optimum sequence of events observed in different wells or sections subject to stratigraphic inconsistencies in the direction of the arrow of time. These inconsistencies, which result in crossovers of lines of correlation between sections, are due to various sampling errors and other sources of uncertainty including reworking and misclassification. They can be resolved by statistical averaging combined with stratigraphic reasoning. Subsequent scaling of the events can be carried out by estimating intervals between successive events along a relative time-scale. This results in the scaled optimum sequence. Either the ranked optimum sequence or the scaled optimum sequence can be used for biozonation and for correlation between sections with error bars to denote precision of the correlation. The observed positions in the sections of different biostratigraphic events can have different degrees of precision. These differences can be evaluated by analysis of variance. Other types of stratigraphic events including logmarkers can be integrated and incorporated with the biostratigraphic events. The purpose of this review paper is to provide a succinct description of RASC as it is today using the Cretaceous microfossil example of Gradstein et al. [Gradstein, F.M., Kaminski, M.A., Agterberg, F.P., 1999. Biostratigraphy and paleoceanography of the Cretaceous Seaway between Norway and Greenland. Earth-Science Reviews] for illustration.

Comparative paleoecology of Paleogene and Neogene mammalian faunas: Trophic structure and composition

Article

May 1995
PALAEOGEOGR PALAEOCL

Trophic structure and composition are examined in two important biotic records, one the Paleogene of Wyoming and Montana, and the other from the Neogene of Pakistan. The Paleogene sequence spans approximately 10 million years and encompasses four North American Land Mammal Ages (Torrejonian, Tiffanian, Clarkforkian, and Wasatchian). The Neogene sequence spans approximately 17 m.y. and includes most of the Miocene and Pliocene with the best documented interval spanning from 16 to 7 Ma. Five basic trophic categories (primary consumers: herbivores, frugivores, omnivores: secondary consumers: insectivores, carnivores) are recognized for Paleogene and Neogene mammals based on tooth morphology, body size, and analogy with modern mammalian groups. The Paleogene mammalian biota is characterized as one in which both trophic structure and taxonomic composition change through the history of the record. The Neogene mammalian biota maintains a relatively consistent trophic structure through most of the record, although taxonomic composition changes substantially through time.Based on comparisons of trophic structure from the Paleogene and Neogene records with that of selected modern mammalian faunas, Paleogene habitats fluctuated between closed, humid forests and more open, drier woodlands. Neogene trophic structure indicates that savanna woodlands were the typical habitat present through most of the sequence. Only after 7 Ma did these woodlands give way to more open grasslands in Pakistan.

Comparative paleoecology of Paleogene and Neogene mammalian Faunas: body-size structure

Article

May 1995
PALAEOGEOGR PALAEOCL

Species size is correlated with many aspects of life history, ecology, and behavior, which means that size changes within species, lineages, and faunas represent an important component of evolutionary paleoecology. Comparison of Paleogene mammalian faunas from the Bighorn, Clarks Fork, and Crazy Mountains basins of Wyoming and Montana with Neogene mammalian faunas from the Siwalik Group of northern Pakistan reveals similarities and differences in patterns of size change through intervals of 10 m.y.

Marine Benthic Diversity: A Comparative Study

Article

May 1968

Howard L. Sanders

In this paper a methodology is presented for measuring diversity based on rarefaction of actual samples. By the use of this technique, a within-habitat analysis was made of the bivalve and polychaete components of soft-bottom marine faunas which differed in latitude, depth, temperature, and salinity. The resulting diversity values were highly correlated with the physical stability and past history of these environments. A stability-time hypothesis was invoked to fit these findings, and, with this hypothesis, predictions were made about the diversities present in certain other environments as yet unstudied. The two types of diversity, based on numerical percentage composition and on number of species, were compared and shown to be poorly correlated with each other. Our data indicated that species number is the more valid diversity measurement. The rarefaction methodology was compared with a number of diversity indexes using identical data. Many of these indexes were markedly influenced by sample size. Good...

Spatial Scaling of Species Composition: Body Masses of North American Land Mammals

Article

Dec 1991

We describe the nonrandom assembly of the North American terrestrial mammalian fauna based on body size and spatial scale. The frequency distribution of body masses among species for the entire continental fauna was highly modal and right skewed, even on a logarithmic scale; the median size of the 465 species was approximately 45 g. In contrast, comparable frequency distributions for 24 small patches of relatively homogeneous habitat were essentially uniform, with approximately equal numbers of species in each logarithmic size class; the median sizes of the 19-37 species ranged from approximately 100 to 2,500 g. Frequency distributions for 21 biomes (large regions of relatively similar vegetation) were intermediate between the continental and local assemblages. This pattern of assembly indicates that species of modal size (20-250 g) tend not to coexist in local habitat patches and they replace each other more frequently from habitat to habitat across the landscape than species of relatively large or sm

Diachrony of mammalian appearance events: Implications for biochronology

Article

Oct 1998
GEOLOGY

John Alroy

A multivariate biochronological analysis of the North American mammal fossil record has established an independent ordering of appearance events for all described genera and species. This geochronologically confirmed hypothesis shows that first and last appearances in different parts of the continent are highly diachronous. Additional results show that (1) despite this diachrony, the new event sequence is compatible with a previously hypothesized sequence of immigrant first appearances; (2) immigrant genera are not particularly widespread, abundant, or synchronous in their appearances; (3) last appearances, large-mammal appearances, and species-level appearances are the most reliable; and (4) most of the observed diachrony appears to result from undersampling. Because diachrony has little effect on the overall multivariate analysis, and because the differences among classes of events are not extreme, joint analyses of all known appearance events are preferable to the a priori selection of particular appearance events as time indicators.

Estimating terrestrial biodiversity through extrapolation

Article

Jan 1994

Coddington Colwell

Both the magnitude and the urgency of the task of assessing global biodiversity require that we make the most of what we know through the use of estimation and extrapolation. Likewise, future biodiversity inventories need to be designed around the use of effective sampling and estimation procedures, especially for `hyperdiverse' groups of terrestrial organisms, such as arthropods, nematodes, fungi, and microorganisms. The challenge of estimating patterns of species richness from samples can be separated into (i) the problem of estimating local species richness, and (ii) the problem of estimating the distinctness, or complementarity, of species assemblages. These concepts apply on a wide range of spatial, temporal, and functional scales. Local richness can be estimated by extrapolating species accumulation curves, fitting parametric distributions of relative abundance, or using non-parametric techniques based on the distribution of individuals among species or of species among samples. We present several of these methods and examine their effectiveness for an example data set. We present a simple measure of complementarity, with some biogeographic examples, and outline the difficult problem of estimating complementarity from samples. Finally, we discuss the importance of using `reference' sites (or sub-sites) to assess the true richness and composition of species assemblages, to measure ecologically significant ratios between unrelated taxa, to measure taxon/sub-taxon (hier-archical) ratios, and to `calibrate' standardized sampling methods. This information can then be applied to the rapid, approximate assessment of species richness and faunal or floral composition at `comparative' sites.

New methods for quantifying macroevolutionary patterns and processes

Abstract

No full-text available

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