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30 results for “Fossil bias”
FIGURE 12 in Tracking biases in the regular echinoid fossil record: The case of Paracentrotus lividus in recent and fossil shallow-water, high-energy environments
FIGURE 12. Relative abundance of Paracentrotus lividus spine remains. A, Is Mesas (Pleistocene-Bulk sample). B, Sa Mesa Longa Beach (Recent-Surface collection). C, Sa Mesa Longa Beach (Bulk sample). N = number of counted specimens.
FIGURE 13 in Tracking biases in the regular echinoid fossil record: The case of Paracentrotus lividus in recent and fossil shallow-water, high-energy environments
FIGURE 13. Biostratinomic signatures (abrasion and encrustation) of spine remains. A, Is Mesas (Pleistocene-Bulk sample). B, Sa Mesa Longa Beach (RecentSurface collection). C, Sa Mesa Longa Beach (RecentBulk sample). N = number of counted specimens
FIGURE 11 in Tracking biases in the regular echinoid fossil record: The case of Paracentrotus lividus in recent and fossil shallow-water, high-energy environments
FIGURE 11. Distribution of ambulacral and interambulacral plates in the two sediment fractions (> 2 mm and 1-2 mm) investigated herein. N = number of counted specimens.
FIGURE 9 in Tracking biases in the regular echinoid fossil record: The case of Paracentrotus lividus in recent and fossil shallow-water, high-energy environments
FIGURE 9. Relative abundance of Paracentrotus lividus test remains. A, Is Mesas (Pleistocene-Bulk sample). B, Sa Mesa Longa Beach (Recent-Surface collection). C, Sa Mesa Longa Beach (Bulk sample). N = number of counted specimens.
FIGURE 10 in Tracking biases in the regular echinoid fossil record: The case of Paracentrotus lividus in recent and fossil shallow-water, high-energy environments
FIGURE 10. Biostratinomic signatures (fragmentation, abrasion and encrustation) of echinoid test remains. A, Is Mesas (Pleistocene-Bulk sample). B, Sa Mesa Longa Beach (Recent-Surface collection). C, Sa Mesa Longa Beach (Recent-Bulk sample). N = number of counted specimens. Numbers (1-11) are explained in Figure 9. Colors: dark grey, light grey and black represent fragmentation, abrasion and encrustation, respectively.
FIGURE 6. A in Tracking biases in the regular echinoid fossil record: The case of Paracentrotus lividus in recent and fossil shallow-water, high-energy environments
FIGURE 6. A, Panoramic view of Sa Mesa Longa Beach (Central-western Sardinia). B-H, Recent remains of Paracentrotus lividus from Sa Mesa Longa. B, Complete denuded test showing encrustation by serpulids. C, Test fragment made up of several ambulacral and interambulacral plates sutured together, showing inter- and intraplate fragmentation and encrustation by coralline algae and the polychaete Spirorbis. D, Internal view of a large test fragment affected by intraplate fragmentation and encrustation by serpulid worms. E, Two interambulacral plates showing abrasion and encrustation by Spirorbis. F, Single ambulacral plates showing fragmentation (white arrow). G, Epiphysis from the jaw apparatus showing fragmentation and abrasion. H, Madreporite from the apical system affected by fragmentation (white arrow). I, Test fragment of Arbacia lixula showing intraplate fracturing. J, Complete test of Echinocyamus pusillus. B, C, D, I, J Scale bar equals 1 cm. E–H scale bars equal 0.5 cm.
FIGURE 7 in Tracking biases in the regular echinoid fossil record: The case of Paracentrotus lividus in recent and fossil shallow-water, high-energy environments
FIGURE 7. Scanning electron micrographs of suture faces in recent Paracentrotus lividus. A, Interradial suture between interambulacral plates showing galleried stereom with galleries running in aboral-oral direction. A1, Detail of the galleried stereom and collagen fibers. B, Adradial suture of interambulacral plates showing galleried stereom. B1, Detail of the parallel galleries and collagen fibers. C, Adapical suture of an interambulacral plates showing knob-like trabecular protrusions and cavities. C1, The close-up shows numerous knob-like protrusions some of which are interconnected to one another in twos, threes or more. D, Adoral suture of ambulacral plates; 1) Radial ridge at the boundary between ambulacral plates (running across perradial sutures) and 2) galleried stereom. A, B, C Scale bars equal 100 µm; A1, B1, C1 Scale bars equal 20 µm. D Scale bar equals 1 mm.
FIGURE 8 in Tracking biases in the regular echinoid fossil record: The case of Paracentrotus lividus in recent and fossil shallow-water, high-energy environments
FIGURE 8. Size-frequency distribution of the rotulae of the Aristotle's lantern both in Pleistocene deposit and recent setting. Each box-plot represents 25 and 75 percent quartile of all values, Q1 and Q3 respectively. Black line inside the box represents the median. Whiskers are drawn from Q1 and Q3 to the largest values less than 1.5 times the Interquartile range (Q1-Q3). N = number of counted specimens.
FIGURE 4. Associated fauna from levels A and B in Tracking biases in the regular echinoid fossil record: The case of Paracentrotus lividus in recent and fossil shallow-water, high-energy environments
FIGURE 4. Associated fauna from levels A and B of the Is Mesas deposit (Late Pleistocene). A, Patella caerulea. B, Diodora gibberula. C, Cerithium vulgatum. D, Hexaplex trunculus. E, Melarhaphe neritoides. F, Acanthocardia tuberculata. G, Irus irus. H, Arca noae. I, Cardita calyculata. J, Cladocora caespitosa. Scale bars equal 1 cm.
FIGURE 5 in Tracking biases in the regular echinoid fossil record: The case of Paracentrotus lividus in recent and fossil shallow-water, high-energy environments
FIGURE 5. Scanning electron micrographs of Paracentrotus remains from Is Mesas. A, Details of an ambulacral column affected by abrasion. B, Two ambulacral plates still sutured together. C, Interambulacral plate showing a cavity possibly related to bioerosion. D, Spine fragment showing fine surface details such as the crenulated milled ring and shaft striation. Scale bars equal 1 mm.
Data from: Persistent body size bias in the fossil record of Cenozoic North American mammals
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Preservation biases in the fossil record distort species ecological niche and distribution models
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Data from: Across space and time: a review of sampling and analytical biases in fossil data across macroecological scales
<p>Quantitative studies of fossil data have proven critical to a number of major macroevolutionary and macroecological discoveries, such as the 'Big 5' mass extinctions of the Phanerozoic. The development and easy accessibility of major meta-data sources such as the Paleobiology Database and Geobiodiversity Database have also spurred the widespread application of these data to testing ecological hypotheses at finer spatiotemporal and phylogenetic scales. However, issues of preservational/taphonomic biases, sampling/collecting biases, taxonomic issues, and analytical choice can impact the degree of interpretative resolution possible, and even obscure biological 'signal' from error/bias-introduced 'noise'. The degree to which these factors can impact analytical interpretations is not well-documented in comparison to the scale of use of these data sources. Here, we review the many forms of systematic error that can creep into a paleoecological study, from the stage of data collection to the interpretation of analytical results, and provide two case studies based upon re-analysis of previously-published datasets to illustrate the varying impacts of such biases. The first case study focuses on the Cambrian Burgess Shale, and the second on the Belly River Group, with both representing highly-sampled, taphonomically characterized, and spatiotemporally-constrained datasets developed through multiple years of sustained field collecting. In the former, we illustrate the impacts of collecting bias through quantitative comparisons of collected vs. discarded specimens over multiple field seasons, illustrating the impact of this data loss on ecological reconstructions and analysis. In the latter case study, we review the impact of preservational biases, the approaches to their quantification and mitigation, where these approaches have led to misinterpretations in the past, and the differences in ecological resolution that result from occurrence vs abundance approaches in macroecological analysis. Lastly, we synthesize these case studies with our review of past approaches to propose a series of recommendations for future paleoecological and macroecological studies, emphasizing the continued importance of high-quality primary data and ongoing need for a first-principles approach to address existing issues of missing data.</p>
Data from: Phylogeny, palaeontology, and primates: do incomplete fossils bias the tree of life?
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Data from: Across space and time: a review of sampling and analytical biases in fossil data across macroecological scales
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Data from: Taxonomic structure of the fossil record is shaped by sampling bias
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Data from: How many dinosaur species were there? Fossil bias and true richness estimated using a Poisson sampling model
The fossil record is a rich source of information about biological diversity in the past. However, the fossil record is not only incomplete but has also inherent biases due to geological, physical, chemical and biological factors. Our knowledge of past life is also biased because of differences in academic and amateur interests and sampling efforts. As a result, not all individuals or species that lived in the past are equally likely to be discovered at any point in time or space. To reconstruct temporal dynamics of diversity using the fossil record, biased sampling must be explicitly taken into account. Here, we introduce an approach that uses the variation in the number of times each species is observed in the fossil record to estimate both sampling bias and true richness. We term our technique TRiPS (True Richness estimated using a Poisson Sampling model) and explore its robustness to violation of its assumptions via simulations. We then venture to estimate sampling bias and absolute species richness of dinosaurs in the geological stages of the Mesozoic. Using TRiPS, we estimate that 1936 (1543–2468) species of dinosaurs roamed the Earth during the Mesozoic. We also present improved estimates of species richness trajectories of the three major dinosaur clades: the sauropodomorphs, ornithischians and theropods, casting doubt on the Jurassic–Cretaceous extinction event and demonstrating that all dinosaur groups are subject to considerable sampling bias throughout the Mesozoic.
Data from: Bias and sensitivity in the placement of fossil taxa resulting from interpretations of missing data
The utility of fossils in evolutionary contexts is dependent on their accurate placement in phylogenetic frameworks, yet intrinsic and widespread missing data make this problematic. The complex taphonomic processes occurring during fossilization can make it difficult to distinguish absence from non-preservation, especially in the case of exceptionally preserved soft-tissue fossils: is a particular morphological character (e.g. appendage, tentacle or nerve) missing from a fossil because it was never there (phylogenetic absence), or just happened to not be preserved (taphonomic loss)? Missing data has not been tested in the context of interpretation of non-present anatomy nor in the context of directional shifts and biases in affinity. Here, complete taxa, both simulated and empirical, are subjected to data loss through the replacement of present entries (1s) with either missing (?s) or absent (0s) entries. Both cause taxa to drift down trees, from their original position, toward the root. Absolute thresholds at which downshift is significant are extremely low for introduced absences (2 entries replaced, 6 % of present characters). The opposite threshold in empirical fossil taxa is also found to be low; two absent entries replaced with presences causes fossil taxa to drift up trees. As such, only a few instances of non-preserved characters interpreted as absences will cause fossil organisms to be erroneously interpreted as more primitive than they were in life. This observed sensitivity to coding non-present morphology presents a problem for all evolutionary studies that attempt to use fossils to reconstruct rates of evolution or unlock sequences of morphological change. Stem-ward slippage, whereby fossilization processes cause organisms to appear artificially primitive, appears to be a ubiquitous and problematic phenomenon inherent to missing data, even when no decay biases exist. Absent characters therefore require explicit justification and taphonomic frameworks to support their interpretation.
Supplementary information for: A biased fossil record can preserve reliable phylogenetic signal
<p><span><span><span><span><span><span><span><span><span><span><span><span><i>Abstract.</i><b>––</b>The fossil record is notoriously imperfect and biased in representation, hindering our ability to place fossil specimens into an evolutionary context. For groups with fossil records mostly consisting of disarticulated parts (e.g., vertebrates, echinoderms, plants), the limited morphological information preserved sparks concerns about whether fossils retain reliable evidence of phylogenetic relationships, and lends uncertainty to analyses of diversification, paleobiogeography, and biostratigraphy in Earth history. To address whether a fragmentary past can be trusted, we need to assess whether incompleteness affects the quality of phylogenetic information contained in fossil data. Herein, we characterize skeletal incompleteness bias in a large dataset (6,585 specimens; 14,417 skeletal elements) of fossil squamates (lizards, snakes, amphisbaenians, and mosasaurs). We show that jaws + palatal bones, vertebrae, and ribs appear more frequently in the fossil record than other parts of the skeleton. This incomplete anatomical representation in the fossil record is biased against regions of the skeleton that contain the majority of morphological phylogenetic characters used to assess squamate evolutionary relationships. Despite this bias, parsimony- and model-based comparative analyses indicate that the most frequently-occurring parts of the skeleton in the fossil record retain similar levels of phylogenetic signal as parts of the skeleton that are rarer. These results demonstrate that the biased squamate fossil record contains reliable phylogenetic information, and support our ability to place incomplete fossils in the Tree of Life. </span></span></span></span></span></span></span></span></span></span></span></span></p>
FIGURE 3 in Tracking biases in the regular echinoid fossil record: The case of Paracentrotus lividus in recent and fossil shallow-water, high-energy environments
FIGURE 3. Remains of Paracentrotus lividus from Level A of the Is Mesas deposit (Late Pleistocene). A, 1) Fragment of test consisting of ambulacral and interambulacral plates still sutured together and showing interplate fracturing; 2) Isolated plates; 3) Fragments; 4) Spines. B, Large portion of ambulacral column showing intraplate fragmentation. C, Large portion of interambulacral column. D, Fragmented interambulacral plate. E, Madreporite. F, Hemipyramid. G, Rotula. H, Complete spine. A-C, H Scale bars equal 1 cm. E-G Scale bars equal 0.5 cm.
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