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in category paleontology

186 results found. For more information, click each entry to expand.

81: Diverse stem-chondrichthyan oral structures and evidence for an independently acquired acanthodid dentition
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Posted 10 Jul 2020

Diverse stem-chondrichthyan oral structures and evidence for an independently acquired acanthodid dentition
700 downloads bioRxiv paleontology

Richard P Dearden, Sam Giles

The teeth of sharks famously form a series of parallel, continuously replacing files borne directly on the jaw cartilages, in contrast to the site-specific, dermal plate-borne dentition of bony fishes. A major obstacle in understanding how this system evolved is the poorly understood relationships of the earliest chondrichthyans and the profusion of morphologically and terminologically diverse bones, cartilages, splints and whorls that they possess. Here we use tomographic methods to investigate mandibular structures in several early branching acanthodian-grade stem-chondrichthyans. We show that the dentigerous jaw bones of disparate genera of ischnacanthids are united by a common construction, being growing bones with non-shedding dentition. Mandibular splints, which support the ventro-lateral edge of the Meckels cartilage in some taxa, are formed fr om dermal bone and may be an acanthodid synapomorphy. We demonstrate that the teeth of Acanthodopsis are borne directly on the mandibular cartilage and that this taxon is deeply nested within an edentulous radiation, representing an unexpected independent origin of teeth. Many or even all of the range of unusual oral structures may be apomorphic, but they should nonetheless be considered when building hypotheses of tooth and jaw evolution, both in chondrichthyans and more broadly.

82: Integrative isotopic Paleoecology (δ13C, δ18O) of a Late Pleistocene vertebrate community from Sergipe, NE Brazil
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Posted 29 Nov 2018

Integrative isotopic Paleoecology (δ13C, δ18O) of a Late Pleistocene vertebrate community from Sergipe, NE Brazil
697 downloads bioRxiv paleontology

Mário André Trindade Dantas, Alexander Cherkinsky, Carlos Micael Bonfim Lessa, Luciano Vilaboim Santos, Mario Alberto Cozzuol, Érica Cavalcante Omena, Jorge Luiz Lopes da Silva, Alcides Nóbrega Sial, Hervé Bocherens

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.

83: Novel insights into the morphology of Plesiochelys bigleri from the early Kimmeridgian of Northwestern Switzerland
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Posted 19 Mar 2019

Novel insights into the morphology of Plesiochelys bigleri from the early Kimmeridgian of Northwestern Switzerland
687 downloads bioRxiv paleontology

Irena Raselli, Jérémy Anquetin

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 deposits (Lower Virgula Marls and Banné Marls) in the area of Porrentruy (Canton of Jura, Switzerland). This material was revealed by construction works of the A16 Transjurane highway between 2000 and 2011, and led to the recent description of the new species Plesiochelys bigleri. In the years 2014 and 2016, new fragmentary turtle material was collected from the Banné Marls (Reuchenette Formation, lower Kimmeridgian) near the village of Glovelier, Canton of Jura, Switzerland. The new material consists of a complete shell, additional shell elements, a few bones from the appendicular and vertebral skeleton, and a fragmentary basicranium. This material can be confidently assigned to the species P. bigleri. It supports the presence of this species in the Banné Marls, slightly extends its spatial distribution and confirms the differences with the closely related species P. etalloni. The new material reveals that the split between the cerebral and palatine branches of the internal carotid artery occurs in a vertical plane in P. bigleri. This condition could not be observed in the type material due to poor preservation. This new character clearly distinguishes P. bigleri from P. etalloni and seems to be unique among thalassochelydians.

84: Illustrating phylogenetic placement of fossils using RoguePlots: An example from ichneumonid parasitoid wasps (Hymenoptera, Ichneumonidae) and an extensive morphological matrix
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Posted 24 Sep 2018

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

Seraina Klopfstein, Tamara Spasojevic

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, Ichneumonidae) and introduce 'RoguePlots' to illustrate placement uncertainty on the phylogeny of extant taxa. Based on an extensive, newly constructed morphological matrix of 222 characters in 24 fossil and 103 extant taxa, we test three different aspects of models of morphological evolution. We find that a model that includes ordered characters, among-character rate variation, and a state-space restricted to observed states achieves the highest marginal likelihoods. The individual RoguePlots reveal large differences in confidence in the placement of the different fossils and allow some refinements to their classification: Polyhelictes bipolarus and Ichninsum appendicrassum are moved from an uncertain subfamily placement to Pimplinae, Plectiscidea lanhami is transferred to Allomacrus in Cylloceriinae (Allomacrus lanhami, comb. nov.), Lithotorus cressoni is moved from Diplazontinae to Orthocentrinae, and we note uncertainty in the generic placement of Xanthopimpla? messelensis. We discuss potential artefacts that might result in biased posterior probabilities in Bayesian morphological phylogenetic analyses, pertaining to character and taxon sampling, fossilization biases, and model misspecification. Finally, we suggest future directions both in ichneumonid palaeontology, in the modelling of morphological evolution, and in the way Bayesian phylogenetics can improve both assessment and representation of fossil placement uncertainty.

85: 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
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Posted 17 Apr 2019

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
658 downloads bioRxiv paleontology

Andrej Čerňanský, Elena V. Syromyatnikova

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 premaxilla, maxillae, frontals, parietals, jugals, quadrate, pterygoids, dentaries and vertebrae. The comparison of these elements to all extant green lizard species shows that these fossils are indistinguishable from Lacerta trilineata. Thus, they form the first potential evidence of the occurrence of this species in the Miocene. This may be also used as a potential calibration point for further studies. Together with other lizard fossils, Solnechnodolsk shows an interesting combination of survivors and the dawn of modern species. This locality provides important evidence for the transition of an archaic Miocene world to the modern diversity of lizards in Europe. In addition, this article represents a contribution to the knowledge of the comparative osteological anatomy of the selected cranial elements in lacertid. This study gives special emphasis to the green lizards, but new data are also presented for related taxa, e.g., Timon lepidus, Podarcis muralis or Zootoca vivipara. Although the green lizards include several cryptic species for which determination based on isolated osteological material would be expected to be difficult, our comparisons show several important morphological differences.

86: A SUPERNOVA AT 50 PC: EFFECTS ON THE EARTH'S ATMOSPHERE AND BIOTA
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Posted 15 Feb 2017

A SUPERNOVA AT 50 PC: EFFECTS ON THE EARTH'S ATMOSPHERE AND BIOTA
653 downloads bioRxiv paleontology

A.L Melott, B.C. Thomas, M. Kachelrieß, D.V. Semikoz, A.C. Overholt

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 inside a weak, disordered magnetic field at that time, TeV-PeV cosmic rays at Earth will increase by a factor of a few hundred. Tropospheric ionization will increase proportionately, and the overall muon radiation load on terrestrial organisms will increase by a factor of ~150. All return to pre-burst levels within 10kyr. In the case of an ordered magnetic field, effects depend strongly on the field orientation. The upper bound in this case is with a largely coherent field aligned along the line of sight to the supernova, in which case TeV-PeV cosmic ray flux increases are ~10000; in the case of a transverse field they are below current levels. We suggest a substantial increase in the extended effects of supernovae on Earth and in the lethal distance estimate; more work is needed.This paper is an explicit followup to Thomas et al. (2016). We also here provide more detail on the computational procedures used in both works.

87: Endocast and bony labyrinth of a stem gnathostome shed light on the earliest diversification of jawed vertebrates
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Posted 12 Aug 2020

Endocast and bony labyrinth of a stem gnathostome shed light on the earliest diversification of jawed vertebrates
653 downloads bioRxiv paleontology

You-an Zhu, Sam Giles, Gavin Young, Yuzhi Hu, Mohamad Bazzi, Per E. Ahlberg, Min Zhu, Jing Lu

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 and endocast resemble those of jawless vertebrates, its inner ear displays a repertoire of crown gnathostome characters. Both parsimony and Bayesian analyses suggest that established hypotheses of "placoderm" relationships are unstable, with newly-revealed anatomy pointing to a potentially radical revision of early gnathostome evolution. Our results call into question the appropriateness of fusiform "placoderms" as models of primitive gnathostome anatomy and raise questions of homology relating to key cranial features. ### Competing Interest Statement The authors have declared no competing interest.

88: Early Tetrapodomorph Biogeography: Controlling for Fossil Record Bias in Macroevolutionary Analyses
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Posted 06 Aug 2019

Early Tetrapodomorph Biogeography: Controlling for Fossil Record Bias in Macroevolutionary Analyses
646 downloads bioRxiv paleontology

Jacob D. Gardner, Kevin Surya, Chris L. Organ

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 geographic information and test it with a case study on early tetrapodomorph biogeography. We use recently-developed Bayesian phylogeographic models and a new supertree of early tetrapodomorphs to estimate dispersal rates and ancestral habitat locations. We find strong evidence that geographic sampling bias explains supposed radiations in dispersal rate (potential adaptive radiations). Our study highlights the necessity of accounting for geographic sampling bias in macroevolutionary and phylogenetic analyses and provides an approach to test for its effect.

89: The influence of environmental setting on the community ecology of Ediacaran organisms
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Posted 02 Dec 2019

The influence of environmental setting on the community ecology of Ediacaran organisms
644 downloads bioRxiv paleontology

Emily G. Mitchell, Nikolai Bobkov, Natalia Bykova, Alavya Dhungana, Anton Kolesnikov, Ian R. P. Hogarth, Alexander G Liu, Tom M.R. Mustill, Nikita Sozonov, Shuhai Xiao, Dmitriy V. Grazhdankin

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 palaeocommunities exhibit marked differences in the response of their component taxa to sub-metre-scale habitat heterogeneities on the seafloor. Shallow-marine palaeocommunities were heavily influenced by local habitat heterogeneities, in contrast to their deep-water counterparts. Lower species richness in deep-water Ediacaran assemblages compared to shallow-water counterparts across the studied time-interval could have been driven by this environmental patchiness, because habitat heterogeneities correspond to higher diversity in modern marine environments. The presence of grazers and detritivores within shallow-water communities may have promoted local patchiness, potentially initiating a chain of increasing heterogeneity of benthic communities from shallow to deep-marine depositional environments. Our results provide quantitative support for the Savannah hypothesis for early animal diversification, whereby Ediacaran diversification was driven by patchiness in the local benthic environment.

90: How macroecology affects macroevolution: the interplay between extinction intensity and trait-dependent extinction in brachiopods
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Posted 17 Jan 2019

How macroecology affects macroevolution: the interplay between extinction intensity and trait-dependent extinction in brachiopods
640 downloads bioRxiv paleontology

Peter D. Smits

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 a model to understand how the average taxon duration (i.e. fitness) varies over time, to estimate trait-based differences in taxon durations (i.e. selection), and to measure the amount of correlation between taxon fitness and selection. I find evidence for when extinction intensity increases, selection strength on geographic range also increases. I also find strong evidence for a non-linear relationship between environmental preference for epicontinental versus open-ocean environments and expected taxon duration, where taxa with intermediate preferences are expected to have greater durations than environmental specialists. Finally, I find that taxa which appear more frequently in epicontinental environments will have a greater expected duration than those taxa which prefer open-ocean environments. My analysis supports the conclusions that as extinction intensity increases and average fitness decreases, as happens during a mass extinction, the trait-associated differences in fitness would increase. In contrast, during periods of low extinction intensity when fitness is greater than average, my model predicts that selection associated with geographic range and environmental preference would decrease and be less than average.

91: A biologically driven directional change in susceptibility to global-scale glaciation during the Precambrian-Cambrian transition
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Posted 29 Jun 2018

A biologically driven directional change in susceptibility to global-scale glaciation during the Precambrian-Cambrian transition
637 downloads bioRxiv paleontology

Richard A. Boyle, Carolin R. Löscher

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 of glacial inception, but ultimately attributes the SBE phenomenon to unusual tectonic boundary conditions. Here we suggest that the evident directional decrease in Earths susceptibility to a SBE suggests that such a-directional abiotic factors are an insufficient explanation for the lack of SBE events since ~580 Ma. Instead we hypothesize that the terrestrial biospheres capacity to sustain a given level of biotic weathering-enhancement under suboptimal/declining temperatures, itself decreased over time: because lichens (with a relatively robust tolerance of sub-optimal temperatures) were gradually displaced on the land surface by more complex photosynthetic life (with a narrower temperature window for growth). We use a simple modelling exercise to highlight the critical (but neglected) importance of the temperature sensitivity of the biotic weathering enhancement factor and discuss the likely values of key parameters in relation to both experiments and the results of complex climate models. We show how the terrestrial biospheres capacity to sustain a given level of silicate-weathering-induced CO2-drawdown is critical to the temperature/greenhouse forcing at which SBE initiation is conceivable. We do not dispute the importance of low degassing rate and other tectonic factors, but propose that the unique feature of the Neoproterozoic was biologys capacity to tip the system over the edge into a runaway ice-albedo feedback; compensating for the self-limiting decline in weathering rate during the temperature decrease on the approach to glaciation. Such compensation was more significant in the Neoproterozoic than the Phanerozoic due, ultimately, to changes in the species composition of the weathering interface over the course of evolutionary time.

92: A Posteriori Evaluation Of Molecular Divergence Dates Using Empirical Estimates Of Time-Heterogeneous Fossilization Rates
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Posted 18 Apr 2017

A Posteriori Evaluation Of Molecular Divergence Dates Using Empirical Estimates Of Time-Heterogeneous Fossilization Rates
637 downloads bioRxiv paleontology

Simon Gunkel, Jes Rust, Torsten Wappler, Christoph Mayer, Oliver Niehuis, Bernhard Misof

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 empirically derived fossilization rates and evaluates the fit of estimated divergence times to the fossil record. We tested the performance of this measure with simulated data sets. Furthermore, we applied it to the estimated divergence times of (i) Clavigeritae beetles of the family Staphylinidae and (ii) all extant insect orders. The reanalyzed beetle data supports the originally published results, but shows that several fossil calibrations used do not increase the reliability of the divergence time estimates. Analyses of estimated inter-ordinal insect divergences indicate that uniform priors with soft bounds marginally outperform log-normal priors on node ages. Furthermore, a posteriori evaluation of the original published analysis indicates that several inter-ordinal divergence estimates might be too young. The λ statistic allows the comparative evaluation of any clade divergence estimate derived from different calibration approaches. Consequently, the application of different algorithms, software tools, and calibration schemes can be empirically assessed.

93: Rapid Pliocene Diversification of Modern Kangaroos
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Posted 16 May 2018

Rapid Pliocene Diversification of Modern Kangaroos
634 downloads bioRxiv paleontology

Aidan M. C. Couzens, Gavin J. Prideaux

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 emergence. In contrast, low-crowned short-faced kangaroos radiated into browsing niches as the late Cenozoic became more arid, contradicting the view that this was a period of global decline among browsers. Our results link warm intervals with bursts of diversification and undermine arguments attributing Pleistocene megafaunal extinction to aridity-forced dietary change.

94: Quantitative Late Quaternary climate reconstruction from plant macrofossil proxy in Western North America
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Posted 07 Jun 2018

Quantitative Late Quaternary climate reconstruction from plant macrofossil proxy in Western North America
633 downloads bioRxiv paleontology

Robert S Harbert, Kevin C. Nixon

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 individualistic concept of plant community assembly. The results are spatiotemporally specific estimates of temperature, precipitation, available moisture, and seasonal patterns that are consistent with well understood global climate patterns, but provide previously unavailable detail and precision of the regional paleoclimate in western North America. Rapid warming is estimated at the Pleistocene-Holocene transition, at a conservative estimate of ca. 1 degree centigrade per millennium. Previously projected future temperature increases suggest a rate of increase of more than 2 degrees over the next century, an astonishing 10X the rate experienced at any point during the past 50,000 years in Western North America. These analyses form a baseline demonstration of how the growing paleoecological record of packrat midden plant macrofossils is able to provide quantitative estimates of paleoclimate that aid in understanding the complexities of, and biotic responses to the regional climate system.

95: Validation of biosignatures confirms the informative nature of fossil organic Raman spectra
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Posted 08 Feb 2021

Validation of biosignatures confirms the informative nature of fossil organic Raman spectra
623 downloads bioRxiv paleontology

Jasmina Wiemann, Derek E. G. Briggs

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 components contributing to two baselined spectra selected from these studies and claimed similarities with a downloaded edge filter transmission spectrum. On the basis of indirect comparisons and qualitative observations they argued that all spectral features detected, including significant mineral peaks, can be equated to edge filter ripples and are therefore artefactual. Alleon et al. extrapolated this conclusion to dispute not only the validity of n>200 spectra in the studies in question, but also the utility of Raman spectroscopy, a well established method, for analysing organic materials in general. Here we test the claims by Alleon et al. using direct spectral comparisons and statistical analyses. We present multiple independent lines of evidence that demonstrate the original, biologically and geologically informative nature of the Raman spectra in question. We demonstrate that the methodological approach introduced by Alleon et al. is unsuitable for assessing the quality of spectra and identifying noise within them. Statistical analyses of large Raman spectral data sets provide a powerful tool in the search for compositional patterns in biomaterials and yield invaluable insights into the history of life.

96: A way to break bones? The weight of intuitiveness
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Posted 31 Mar 2020

A way to break bones? The weight of intuitiveness
622 downloads bioRxiv paleontology

D. Vettese, T. Stavrova, A. Borel, J. Marin, M.-H. Moncel, M. Arzarello, C. Daujeard

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. culturally influenced. In order to assess the weight of the counter-intuitive factor in the percussion mark pattern distribution, we carried out an experiment that by contrast focuses on the intuitive approach of fracturing bones to extract marrow, involving individual without experience in this activity. We wanted to evaluate the influence of bone morphology and the individuals’ behaviour on the distribution of percussion marks. Twelve experimenters broke 120 limb bones, a series of 10 bones per individual. During the experiment, information concerning the fracture of the bones as well as individual behaviour was collected and was subsequently compared to data from the laboratory study of the remains. Then, we applied an innovative GIS (Geographic Information System) method to analyze the distribution of percussion marks to highlight recurrent patterns. Results show that in spite of all the variables there is a high similarity in the distribution of percussion marks which we consider as intuitive patterns. The factor influenced the distribution for the humerus, radius-ulna and tibia series is the bone morphology, while for the femur series individual behaviour seems to have more weight in the distribution. To go further in the subject we need to compare the intuitive models with the distributions of percussion marks registered in fossil assemblages. Thus, it would be possible to propose new hypotheses on butchering practices based on the results presented in this work. ### Competing Interest Statement The authors have declared no competing interest.

97: Unbiased clade age estimation using a Bayesian Brownian Bridge
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Posted 04 Apr 2021

Unbiased clade age estimation using a Bayesian Brownian Bridge
621 downloads bioRxiv paleontology

Daniele Silvestro, Christine D. Bacon, Wenna Ding, Qiuyue Zhang, Philip Conrad James Donoghue, Alexandre Antonelli, Yaowu Xing

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 particular, we estimated with high probability that crown-angiosperms originated before the Cretaceous (> 145 Ma). Budd and colleagues critique our study, arguing that the BBB model is biased towards older estimates when fossil data are scarce or absent, that our underlying fossil dataset is unsound, that our clade age estimates are therefore biased by early diverging lineages that are underrepresented in the fossil record, and that pooling of fossil data for analysis at higher taxonomic ranks overcomes these biases. Here, we explore their points and perform new simulations to show that their critique has no merit.

98: Saving Old Bones: a non-destructive method for bone collagen prescreening
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Posted 31 May 2019

Saving Old Bones: a non-destructive method for bone collagen prescreening
621 downloads bioRxiv paleontology

Matt Sponheimer, Christina M Ryder, Helen Fewlass, Erin K Smith, William J. Pestle, Sahra Talamo

Bone collagen is an important material for radiocarbon, paleodietary, and paleoproteomic analyses, but it degrades over time. Various methods have been employed to prescreen bone for collagen preservation, but these are often destructive and/or require exportation for analysis. Here we show that near-infrared spectroscopy can be used to determine bone collagen content quickly and non-destructively on site.

99: Messinian vegetation and climate of the intermontane Florina-Ptolemais-Servia Basin, NW Greece inferred from palaeobotanical data: How well do plant fossils reflect past environments?
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Posted 25 Nov 2019

Messinian vegetation and climate of the intermontane Florina-Ptolemais-Servia Basin, NW Greece inferred from palaeobotanical data: How well do plant fossils reflect past environments?
616 downloads bioRxiv paleontology

Johannes M. Bouchal, Tuncay H. Güner, Dimitrios Velitzelos, Evangelos Velitzelos, Thomas Denk

The late Miocene is marked by pronounced environmental changes and the appearance of strong temperature and precipitation seasonality. Although environmental heterogeneity is to be expected during this time, it is challenging to reconstruct palaeoenvironments using plant fossils. We investigated leaves and dispersed spores/pollen from 6.4-6 Ma strata in the intermontane Florina-Ptolemais-Servia Basin (FPS) of northwestern Greece. To assess how well plant fossils reflect the actual vegetation of the FPS, we assigned fossil-taxa to biomes providing a measure for environmental heterogeneity. Additionally, the palynological assemblage was compared to pollen spectra from modern lake sediments to assess biases in spore/pollen representation in the pollen record. We found a close match of the Vegora assemblage with modern Fagus-Abies forests of Turkey. Using taxonomic affinities of leaf fossils, we further established close similarities of the Vegora assemblage with modern laurophyllous oak forests of Afghanistan. Finally, using information from sedimentary environment and taphonomy, we distinguished local and distantly growing vegetation types. We then subjected the plant assemblage of Vegora to different methods of climate reconstruction and discussed their potentials and limitations. Leaf and spore/pollen records allow accurate reconstructions of palaeoenvironments in the FPS, whereas extra-regional vegetation from coastal lowlands is likely not captured. ### Competing Interest Statement The authors have declared no competing interest.

100: The extinction and survival of sharks across the end-Cretaceous mass extinction
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Posted 20 Jan 2021

The extinction and survival of sharks across the end-Cretaceous mass extinction
615 downloads bioRxiv paleontology

Mohamad Bazzi, Nicolás Campione, Per E Ahlberg, Henning Blom, Benjamin Philip Kear

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 examine the dental morphology of multiple shark lineages traversing the catastrophic end-Cretaceous mass extinction -- this event terminated the Mesozoic Era 66 million years ago. Our results show that selachimorphs maintained virtually static levels of dental disparity in most of their constituent clades during the Cretaceous/Paleogene transition. Nevertheless, selective extinctions did impact on apex predator lineages characterized by triangular blade-like teeth, and in particular, lamniforms including the dominant Cretaceous anacoracids. Other groups, such as, triakid carcharhiniforms, squalids, and hexanchids, were seemingly unaffected. Finally, while some lamniform lineages experienced morphological depletion, others underwent a post-extinction disparity increase, especially odontaspidids, which are typified by narrow-cusped teeth adapted for feeding on fishes. This disparity shift coincides with the early Paleogene radiation of teleosts, a possible prey source, as well as the geographic relocation of shark disparity hotspots, perhaps indicating a regionally disjunct pattern of extinction recovery. Ultimately, our study reveals a complex morphological response to the end-Cretaceous mass extinction event, the dynamics of which we are only just beginning to understand.

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