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Results 81 through 100 out of 190

in category paleontology


81: Integrative isotopic Paleoecology (δ13C, δ18O) of a Late Pleistocene vertebrate community from Sergipe, NE Brazil

Mário André Trindade Dantas, Alexander Cherkinsky et al.

723 downloads (posted 29 Nov 2018)

Isotopes are one of the best tools to reconstruct the Paleoecology of extinct taxa, yielding insights about their diet (through carbon; C3 and C4 plants), niche breadth (BA) and the environment in which they lived. In the present work we go deeper in the use of isotopes and explore a mathematical mixing model with the stable isotopes of two elements (carbon and oxygen) to (1) suggest the relative contribution of four types of food resources (leaves, fruits, roots and C4 grass) for meso- and megaherbivores (weight > 100 kg) that lived in the Late Pleistocene of Poco Redondo, Sergipe, Brasil, and (2) evaluate which of these herbivores could be the potential prey for the carnivores Smilodon populator and Caiman latirostris. To explore the intra/interspecific competition of these fauna, we generate weight estimation, standardized niche breadth (BA) for the meso-megamammals from Sergipe and compare with data from the meso-megaherbivores from Africa, concluding that Eremotherium laurillardi and Toxodon platensis were the best resource competitors in the Late Pleistocene of Sergipe, and reinforcing their importance as key species in this extinct community. Finally, we reconstructed the paleoenvironment in which the vertebrate community of Sergipe lived, estimating Mean Annual Temperature (C), Mean Annual Precipitation, Biomass and Energy Expendidure, noting that environments in the Late Pleistocene of Sergipe were similar to those of Africa nowadays, but hotter and with more energy expenditure for these meso-megamammals.


82: Improved estimation of macroevolutionary rates from fossil data using a Bayesian framework

Daniele Silvestro, Alexandre Antonelli et al.

711 downloads (posted 09 May 2018)

The estimation of origination and extinction rates and their temporal variation is central to understanding diversity patterns and the evolutionary history of clades. The fossil record provides the most direct evidence of extinction and biodiversity changes through time and has long been used to infer the dynamics of diversity changes in deep time. The software PyRate implements a Bayesian framework to analyze fossil occurrence data to estimate the rates of preservation, origination and extinction while incorporating se...


83: Novel insights into the morphology of Plesiochelys bigleri from the early Kimmeridgian of Northwestern Switzerland

Irena Raselli, Jérémy Anquetin

698 downloads (posted 19 Mar 2019)

Plesiochelyidae were relatively large coastal marine turtles, which inhabited the epicontinental seas of Western Europe during the Late Jurassic. Their fossil record can be tracked in Germany, Switzerland, the United Kingdom, France, Spain and Portugal. The Jura Mountains, in northwestern Switzerland, have been the main source for the study of this group, mostly thanks to the rich and famous historical locality of Solothurn. In the last two decades, numerous plesiochelyid remains have been collected from Kimmeridgian de...


84: Early Tetrapodomorph Biogeography: Controlling for Fossil Record Bias in Macroevolutionary Analyses

Jacob D. Gardner, Kevin Surya et al.

687 downloads (posted 06 Aug 2019)

The fossil record provides direct empirical data for understanding macroevolutionary patterns and processes. Inherent biases in the fossil record are well known to confound analyses of this data. Sampling bias proxies have been used as covariates in regression models to test for such biases. Proxies, such as formation count, are associated with paleobiodiversity, but are insufficient for explaining species dispersal owing to a lack of geographic context. Here, we develop a sampling bias proxy that incorporates geographi...


85: Endocast and bony labyrinth of a stem gnathostome shed light on the earliest diversification of jawed vertebrates

You-an Zhu, Sam Giles et al.

682 downloads (posted 12 Aug 2020)

Our understanding of the earliest evolution of jawed vertebrates depends on a credible phylogenetic assessment of the jawed stem gnathostomes collectively known as "placoderms". However, their relationships, and even whether "placoderms" represent a single radiation or a paraphyletic array, remain contentious. Here we describe the endocranial cavity and inner ear of Brindabellaspis stensioi , commonly recovered as a taxon of uncertain affinity branching near the base of "placoderms". While some features of its braincase...



A.L Melott, B.C. Thomas et al.

674 downloads (posted 15 Feb 2017)

Recent 60Fe results have suggested that the estimated distances of supernovae in the last few million years should be reduced from ~100 pc to ~50 pc. Two events or series of events are suggested, one about 2.7 million years to 1.7 million years ago, and another may at 6.5 to 8.7 million years ago. We ask what effects such supernovae are expected to have on the terrestrial atmosphere and biota. Assuming that the Local Bubble was formed before the event being considered, and that the supernova and the Earth were both insi...


87: Illustrating phylogenetic placement of fossils using RoguePlots: An example from ichneumonid parasitoid wasps (Hymenoptera, Ichneumonidae) and an extensive morphological matrix

Seraina Klopfstein, Tamara Spasojevic

673 downloads (posted 24 Sep 2018)

The fossil record constitutes the primary source of information about the evolutionary history of extant and extinct groups, and many analyses of macroevolution rely on fossils that are accurately placed within phylogenies. To avoid misinterpretation of the fossil record, especially by non-palaeontologists, the proper assessment and communication of uncertainty in fossil placement is crucial. We here use Bayesian morphological phylogenetics to evaluate the classifications of fossil parasitoid wasps (Hymenoptera, Ichneum...


88: Validation of biosignatures confirms the informative nature of fossil organic Raman spectra

Jasmina Wiemann, Derek E. G. Briggs

668 downloads (posted 08 Feb 2021)

Raman spectroscopy has facilitated rapid progress in the understanding of patterns and processes associated with biomolecule fossilization and revealed the preservation of biological and geological signatures in fossil organic matter. Nonetheless six large-scale statistical studies of Raman spectra of carbonaceous fossils, selected from a number of independent assessments producing similar trends, have been disputed. Alleon et al. applied a wavelet transform analysis in an unconventional way to identify frequency compon...


89: The first Miocene fossils of Lacerta cf. trilineata (Squamata, Lacertidae) with a comparative study of the main cranial osteological differences in green lizards and their relatives

Andrej Čerňanský, Elena V. Syromyatnikova

663 downloads (posted 17 Apr 2019)

We here describe the first fossil remains of a green lizardof the Lacerta group from the late Miocene (MN 13) of the Solnechnodolsk locality in southern European Russia. This region of Europe is crucial for our understanding of the paleobiogeography and evolution of these middle-sized lizards. Although this clade has a broad geographical distribution across the continent today, its presence in the fossil record has only rarely been reported. In contrast to that, the material described here is abundant, consists of a pre...


90: A Posteriori Evaluation Of Molecular Divergence Dates Using Empirical Estimates Of Time-Heterogeneous Fossilization Rates

Simon Gunkel, Jes Rust et al.

659 downloads (posted 18 Apr 2017)

The application of molecular clock concepts in phylogenetics permits estimating the divergence times of clades with an incomplete fossil record. However, the reliability of this approach is disputed, because the resulting estimates are often inconsistent with different sets of fossils and other parameters (clock models and prior settings) in the analyses. Here, we present the λ statistic, a likelihood approach for a posteriori evaluating the reliability of estimated divergence times. The λ statistic is based on empirica...


91: How macroecology affects macroevolution: the interplay between extinction intensity and trait-dependent extinction in brachiopods

Peter D. Smits

658 downloads (posted 17 Jan 2019)

Selection is the force behind differences in fitness, with extinction being the most extreme example of selection. Modern experiments and observations have shown that average fitness and selection strength can vary over time and space. This begs the question: as average fitness increases, does selection strength increase or decrease? The fossil record illustrates how extinction rates have varied through time, with periods of both rapid and slow species turnover. Using Paleozoic brachiopods as a study system, I developed...


92: A biologically driven directional change in susceptibility to global-scale glaciation during the Precambrian-Cambrian transition

Richard A. Boyle, Carolin R. Löscher

657 downloads (posted 29 Jun 2018)

Integrated geological evidence suggests that grounded ice sheets occurred at sea level across all latitudes during two intervals within the Neoproterozoic era; the snowball Earth (SBE) events. Glacial events at ~730 and ~650 million years ago (Ma) were probably followed by a less severe but nonetheless global-scale glaciation at ~580Ma, immediately preceding the proliferation of the first fossils exhibiting unambiguous animal-like form. Existing modelling identifies weathering-induced CO2-drawdown as a critical aspect o...


93: A way to break bones? The weight of intuitiveness

D. Vettese, T. Stavrova et al.

656 downloads (posted 31 Mar 2020)

During the Middle Paleolithic period, bone marrow extraction was an essential source of fat nutrients for hunter-gatherers especially throughout cold and dry seasons. This is attested by the recurrent findings of percussion marks in osteological material from anthropized archaeological levels. Among them some showed indicators that the marrow extraction process was part of a butchery cultural practice, meaning that the inflicted fracturing gestures and techniques were recurrent, standardized and counter-intuitive i.e. c...


94: The extinction and survival of sharks across the end-Cretaceous mass extinction

Mohamad Bazzi, Nicolás Campione et al.

655 downloads (posted 20 Jan 2021)

Sharks (Selachimorpha) are iconic marine predators that have survived multiple mass extinctions over geologic time. Their fossil record is represented by an abundance of teeth, which traditionally formed the basis for reconstructing large-scale diversity changes among different selachimorph clades. By contrast, corresponding patterns in shark ecology, as measured through morphological disparity, have received comparatively limited analytical attention. Here, we use a geometric morphometric approach to comprehensively ex...


95: Rapid Pliocene Diversification of Modern Kangaroos

Aidan M. C. Couzens, Gavin J. Prideaux

655 downloads (posted 16 May 2018)

Differentiating between ancient and rapidly-evolved clades is critical for understanding impacts of environmental change on biodiversity. Australia possesses many aridity-adapted lineages, the origins of which have been linked by molecular evidence to late Miocene drying. Using dental macrowear and molar crown-height measurements spanning the past 25 million years, we show that the most iconic of Australia's terrestrial mammals, 'true' kangaroos and wallabies (Macropodini), diversified in response to Pliocene grassland ...


96: Quantitative Late Quaternary climate reconstruction from plant macrofossil proxy in Western North America

Robert S Harbert, Kevin C. Nixon

654 downloads (posted 07 Jun 2018)

The Late Quaternary packrat (Neotoma spp.) midden plant macrofossil record in western North America is an exceptional record of biotic change that provides strong evidence of past climate. In this study we generate quantitative estimates of climate from plant community composition of more than 600 individual paleomiddens over the past 50,000 years. This is the first large-scale application of CRACLE, a quantitative climate inference method that uses plant community composition as a climatic proxy under and individualist...


97: Dinosaur bonebed amber from an original swamp forest soil

Sergio Álvarez-Parra, Ricardo Pérez-de la Fuente et al.

651 downloads (posted 16 Sep 2021)

Dinosaur bonebeds with amber content, yet scarce, offer a superior wealth and quality of data on ancient terrestrial ecosystems. However, the preserved palaeodiversity and/or taphonomic characteristics of these exceptional localities had hitherto limited their palaeobiological potential. Here we describe the amber from the Lower Cretaceous dinosaur bonebed of Arino (Teruel, Spain) using a multidisciplinary approach. Amber is found in both a root layer with amber strictly in situ and a litter layer namely composed of aer...


98: The influence of environmental setting on the community ecology of Ediacaran organisms

Emily G. Mitchell, Nikolai Bobkov et al.

650 downloads (posted 02 Dec 2019)

The broad-scale environment plays a substantial role in shaping modern marine ecosystems, but the degree to which palaeocommunities were influenced by their environment is unclear. To investigate how broad-scale environment influenced the community ecology of early animal ecosystems we employed spatial point process analyses to examine the community structure of seven bedding-plane assemblages of late Ediacaran age (558 to 550 Ma), drawn from a range of environmental settings and global localities. The studied palaeocom...


99: Unbiased clade age estimation using a Bayesian Brownian Bridge

Daniele Silvestro, Christine D Bacon et al.

647 downloads (posted 04 Apr 2021)

In a recent paper we presented a new model, the Bayesian Brownian Bridge (BBB), to infer clade age based on fossil evidence and modern diversity. We benchmarked the method with extensive simulations, including a wide range of diversification histories and sampling heterogeneities that go well beyond the necessarily simplistic model assumptions. Applying BBB to 198 angiosperm families, we found that their fossil record is compatible with clade origins earlier than most contemporary palaeobotanical interpretations. In par...


100: First report of the Eocene bivalve Schedocardia (Mollusca, Cardiidae) from Cuba

Johanset Orihuela, Yasmani Ceballos Izquierdo et al.

646 downloads (posted 04 Feb 2020)

Herein we provide the first report of the rare cardiid bivalve Schedocardia from Cuba. The single, partial, valve external mold was derived from the Madruga Formation which is characterized by a richly diverse marine fauna including echinoderms, brachiopods, benthic and planktonic foraminiferans, but from which bivalves were not previously reported. The unit is considered late Paleocene in age (Thanetian), but the presence of Schedocardia supports a possible age extension of the formation into the early Eocene (Ypresian...