Certain geological periods have significantly fewer fossil specimens due to preservation biases.
the verdict
SUPPORTED
the evidence backs this
refutedsupported
the weight of evidence
5 sources for · 0 against
Peer-reviewed literature and reference materials confirm that the quality, abundance, and completeness of the fossil record vary significantly across geological periods due to persistent taphonomic, preservation, and sampling biases.
Many palaeobiological analyses have concluded that modern birds (Neornithes) radiated no earlier than the Maastrichtian, whereas molecular clock studies have argued for a much earlier origination. Here, we assess the quality of the fossil record of Mesozoic avian species, using a recently proposed character completeness metric which calculates the percentage of phylogenetic characters that can be scored for each taxon. Estimates of fossil record quality are plotted against geological time and compared to estimates of species level diversity, sea level, and depositional environment. Geographical controls on the avian fossil record are investigated by comparing the completeness scores of species in different continental regions and latitudinal bins. Avian fossil record quality varies greatly with peaks during the Tithonian-early Berriasian, Aptian, and Coniacian-Santonian, and troughs during the Albian-Turonian and the Maastrichtian. The completeness metric correlates more strongly with a 'sampling corrected' residual diversity curve of avian species than with the raw taxic diversity curve, suggesting that the abundance and diversity of birds might influence the probability of high quality specimens being preserved. There is no correlation between avian completeness and sea level, the number of fluviolacustrine localities or a recently constructed character completeness metric of sauropodomorph dinosaurs. Comparisons between the completeness of Mesozoic birds and sauropodomorphs suggest that small delicate vertebrate skeletons are more easily destroyed by taphonomic processes, but more easily preserved whole. Lagerstätten deposits might therefore have a stronger impact on reconstructions of diversity of smaller organisms relative to more robust forms. The relatively poor quality of the avian fossil record in the Late Cretaceous combined with very patchy regional sampling means that it is possible neornithine lineages were present throughout this interval but have not yet been sampled or are difficult to identify because of the fragmentary nature of the specimens.
Abstract We know that the fossil record is incomplete. But how incomplete? Here we very coarsely estimate the completeness of the mammalian record in the Miocene, assuming that the duration of a mammalian species is about 1 Myr and the species diversity has stayed constant and is structurally comparable to the taxonomic diversity today. The overall completeness under these assumptions appears to be around 4%, but there are large differences across taxonomic groups. We find that the fossil record of proboscideans and perissodactyls as we know it for the Miocene must be close to complete, while we might know less than 15% of the species of artiodactyl or carnivore fossil species and only about 1% of primate species of the Miocene. The record of small mammals appears much less complete than that of large mammals.
Body size is a key organismal trait with profound implications ranging from individual physiology to large-scale macroecological or macroevolutionary phenomena. Among extant terrestrial vertebrates, peak diversity commonly occurs at small body size. Similarities between the body size distributions of fossil and extant mammals have been used to argue that fossil record signals are robust, yet preservation and collector biases disproportionately favour the sampling of large taxa and probably under-represent small-sized diversity. Here, we quantify the effects of these biases on the body size distributions of North American mammals through the Cenozoic. We assess how these distributions have changed with new palaeontological discoveries and evaluate sampling standardization as a potential correction for body size bias. Our results show bias in the mammal record to be persistent and severe. Sampling standardization has no consistent effect on recovered distribution shape probably because sample coverage estimators cannot account for changes in the scope of the sampling universe driven by a combination of historical worker interest and the preservational characteristics of a small pool of formations. Short of a novel standardization method that can account for publication biases, deriving non-artefactual fossil body size signals may ultimately depend on targeted, systematic sampling of exceptional deposits.
<h4>Background and aims</h4>The bryophyte fossil record is less abundant and diverse than predicted by the age of the group and as compared to the fossil record of younger plant groups. Taphonomic biases explain only partially its scarcity. Here, we investigate whether and how recently recognized megabiases that have the potential to affect the fossil record, in general, determine the structure of the bryophyte fossil record.<h4>Methods</h4>We update the pre-Miocene bryophyte fossil record with an ~30 % increase since its latest review (in 2018) and examine fossil bryophyte diversity against the temporal and spatial distribution of the rock record, and economic geography, to document patterns in potential presence, discovery and study of bryophyte fossils.<h4>Key results</h4>Fossil bryophyte abundance is not correlated with the area of rocks exposed around the planet for different geological ages. More fossil bryophytes are known from younger rocks due to the overall richer fossil content of those rocks. More fossil bryophytes have been documented from the Northern Hemisphere, from developed countries, from countries where English is the official language and from countries where more specialists are exploring the fossil record.<h4>Conclusions</h4>The discovery and documentation of bryophyte fossils are biased by socio-economic and language factors, which affect significantly the structure of the fossil record of the group, at least in terms of taxonomic diversity. 'Parachute science' did not and does not significantly influence the documentation of fossil bryophytes.
due to biases towards the preservation and discovery of more recent environments over older ones, where the field of taphonomy can become significant
Paleontology or palaeontology is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geologic time, and assess the interactions between prehistoric organisms and their natural environment. While paleontological observations are known from at least the 6th century BC, the foundat
Paleoecolo…
Everything we examined (5)
This check searched the claim as stated. It did not run a separate search for evidence against it.