scholarly journals Completeness of the eutherian mammal fossil record and implications for reconstructing mammal evolution through the Cretaceous/Paleogene mass extinction

Paleobiology ◽  
2017 ◽  
Vol 43 (4) ◽  
pp. 521-536 ◽  
Author(s):  
Thomas W. Davies ◽  
Mark A. Bell ◽  
Anjali Goswami ◽  
Thomas J. D. Halliday
Keyword(s):  
Mass Extinction ◽  
Fossil Record ◽  
Information Criterion ◽  
Molecular Data ◽  
Tectonic Activity ◽  
Eutherian Mammal ◽  
Geological Time ◽  
Data Set ◽  
Significant Difference ◽  
The Difference

AbstractThere is a well-established discrepancy between paleontological and molecular data regarding the timing of the origin and diversification of placental mammals. Molecular estimates place interordinal diversification dates in the Cretaceous, while no unambiguous crown placental fossils have been found prior to the end-Cretaceous mass extinction. Here, the completeness of the eutherian fossil record through geological time is evaluated to assess the suggestion that a poor fossil record is largely responsible for the difference in estimates of placental origins. The completeness of fossil specimens was measured using the character completeness metric, which quantifies the completeness of fossil taxa as the percentage of phylogenetic characters available to be scored for any given taxon. Our data set comprised 33 published cladistic matrices representing 445 genera, of which 333 were coded at the species level.There was no significant difference in eutherian completeness across the Cretaceous/Paleogene (K/Pg) boundary. This suggests that the lack of placental mammal fossils in the Cretaceous is not due to a poor fossil record but more likely represents a genuine absence of placental mammals in the Cretaceous. This result supports the “explosive model” of early placental evolution, whereby placental mammals originated around the time of the K/Pg boundary and diversified soon after.No correlation was found between the completeness pattern observed in this study and those of previous completeness studies on birds and sauropodomorph dinosaurs, suggesting that different factors affect the preservation of these groups. No correlations were found with various isotope proxy measures, but Akaike information criterion analysis found that eutherian character completeness metric scores were best explained by models involving the marine-carbonate strontium-isotope ratios (87Sr/86Sr), suggesting that tectonic activity might play a role in controlling the completeness of the eutherian fossil record.

Estimating the number of pulses in a mass extinction

Paleobiology ◽  
2018 ◽  
Vol 44 (2) ◽  
pp. 199-218 ◽  
Author(s):  
Steve C. Wang ◽  
Ling Zhong
Keyword(s):  
Mass Extinction ◽  
Fossil Record ◽  
Nearest Neighbor ◽  
Hypothesis Test ◽  
Information Criterion ◽  
Data Set ◽  
Recovery Potential ◽  
Step Algorithm ◽  
Extinction Events ◽  
Fossil Preservation

AbstractThe Signor-Lipps effect states that even a sudden mass extinction will invariably appear gradual in the fossil record, due to incomplete fossil preservation. Most previous work on the Signor–Lipps effect has focused on testing whether taxa in a mass extinction went extinct simultaneously or gradually. However, many authors have proposed scenarios in which taxa went extinct in distinct pulses. Little methodology has been developed for quantifying characteristics of such pulsed extinction events. Here we introduce a method for estimating the number of pulses in a mass extinction, based on the positions of fossil occurrences in a stratigraphic section. Rather than using a hypothesis test and assuming simultaneous extinction as the default, we reframe the question by asking what number of pulses best explains the observed fossil record.Using a two-step algorithm, we are able to estimate not just the number of extinction pulses but also a confidence level or posterior probability for each possible number of pulses. In the first step, we find the maximum likelihood estimate for each possible number of pulses. In the second step, we calculate the Akaike information criterion and Bayesian information criterion weights for each possible number of pulses, and then apply ak-nearest neighbor classifier to these weights. This method gives us a vector of confidence levels for the number of extinction pulses—for instance, we might be 80% confident that there was a single extinction pulse, 15% confident that there were two pulses, and 5% confident that there were three pulses. Equivalently, we can state that we are 95% confident that the number of extinction pulses is one or two. Using simulation studies, we show that the method performs well in a variety of situations, although it has difficulty in the case of decreasing fossil recovery potential, and it is most effective for small numbers of pulses unless the sample size is large. We demonstrate the method using a data set of Late Cretaceous ammonites.

scholarly journals The Coefficient of Variation of Step Time Can Overestimate Gait Abnormality: Test-Retest Reliability of Gait-Related Parameters Obtained with a Tri-Axial Accelerometer in Healthy Subjects

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 577 ◽  
Author(s):  
Shunrou Fujiwara ◽  
Shinpei Sato ◽  
Atsushi Sugawara ◽  
Yasumasa Nishikawa ◽  
Takahiro Koji ◽  
...  
Keyword(s):  
Coefficient Of Variation ◽  
Intraclass Correlation ◽  
Step Length ◽  
Gait Parameter ◽  
Data Set ◽  
Gait Abnormality ◽  
Significant Difference ◽  
Assessment Time ◽  
The Difference ◽  
Gait Abnormalities

The aim of this study was to investigate whether variation in gait-related parameters among healthy participants could help detect gait abnormalities. In total, 36 participants (21 men, 15 women; mean age, 35.7 ± 9.9 years) performed a 10-m walk six times while wearing a tri-axial accelerometer fixed at the L3 level. A second walk was performed ≥1 month after the first (mean interval, 49.6 ± 7.6 days). From each 10-m data set, the following nine gait-related parameters were automatically calculated: assessment time, number of steps, stride time, cadence, ground force reaction, step time, coefficient of variation (CV) of step time, velocity, and step length. Six repeated measurement values were averaged for each gait parameter. In addition, for each gait parameter, the difference between the first and second assessments was statistically examined, and the intraclass correlation coefficient (ICC) was calculated with the level of significance set at p < 0.05. Only the CV of step time showed a significant difference between the first and second assessments (p = 0.0188). The CV of step time also showed the lowest ICC, at <0.50 (0.425), among all parameters. Test–retest results of gait assessment using a tri-axial accelerometer showed sufficient reproducibility in terms of the clinical evaluation of all parameters except the CV of step time.

The biology of mass extinction: a palaeontological view

1989 ◽  
Vol 325 (1228) ◽  
pp. 357-368 ◽  
Keyword(s):  
Mass Extinction ◽  
Large Scale ◽  
Individual Species ◽  
Ecological Groups ◽  
Mass Extinctions ◽  
Geological Time ◽  
Evolutionary Patterns ◽  
Data Set ◽  
High Species Richness ◽  
Extinction Events

Extinctions are not biologically random: certain taxa or functional/ecological groups are more extinction-prone than others. Analysis of molluscan survivorship patterns for the end-Cretaceous mass extinctions suggests that some traits that tend to confer extinction resistance during times of normal (‘background’) levels of extinction are ineffectual during mass extinction. For genera, high species-richness and possession of widespread individual species imparted extinction-resistance during background times but not during the mass extinction, when overall distribution of the genus was an important factor. Reanalysis of Hoffman’s (1986) data ( Neues Jb. Geol. Palaont. Abh. 172, 219) on European bivalves, and preliminary analysis of a new northern European data set, reveals a similar change in survivorship rules, as do data scattered among other taxa and extinction events. Thus taxa and adaptations can be lost not because they were poorly adapted by the standards of the background processes that constitute the bulk of geological time, but because they lacked - or were not linked to - the organismic, species-level or clade-level traits favoured under mass-extinction conditions. Mass extinctions can break the hegemony of species-rich, well-adapted clades and thereby permit radiation of taxa that had previously been minor faunal elements; no net increase in the adaptation of the biota need ensue. Although some large-scale evolutionary trends transcend mass extinctions, post-extinction evolutionary pathways are often channelled in directions not predictable from evolutionary patterns during background times.

scholarly journals The Continuing Debate on Deep Molluscan Phylogeny: Evidence for Serialia (Mollusca, Monoplacophora + Polyplacophora)

2013 ◽  
Vol 2013 ◽  
pp. 1-18 ◽  
Author(s):  
I. Stöger ◽  
J. D. Sigwart ◽  
Y. Kano ◽  
T. Knebelsberger ◽  
B. A. Marshall ◽  
...  
Keyword(s):  
Molecular Clock ◽  
Fossil Record ◽  
Molecular Data ◽  
Approximately Unbiased ◽  
Data Set ◽  
Late Cambrian ◽  
Molluscan Shell ◽  
Rapid Divergence ◽  
Multiple Species

Molluscs are a diverse animal phylum with a formidable fossil record. Although there is little doubt about the monophyly of the eight extant classes, relationships between these groups are controversial. We analysed a comprehensive multilocus molecular data set for molluscs, the first to include multiple species from all classes, including five monoplacophorans in both extant families. Our analyses of five markers resolve two major clades: the first includes gastropods and bivalves sister to Serialia (monoplacophorans and chitons), and the second comprises scaphopods sister to aplacophorans and cephalopods. Traditional groupings such as Testaria, Aculifera, and Conchifera are rejected by our data with significant Approximately Unbiased (AU) test values. A new molecular clock indicates that molluscs had a terminal Precambrian origin with rapid divergence of all eight extant classes in the Cambrian. The recovery of Serialia as a derived, Late Cambrian clade is potentially in line with the stratigraphic chronology of morphologically heterogeneous early mollusc fossils. Serialia is in conflict with traditional molluscan classifications and recent phylogenomic data. Yet our hypothesis, as others from molecular data, implies frequent molluscan shell and body transformations by heterochronic shifts in development and multiple convergent adaptations, leading to the variable shells and body plans in extant lineages.

Assessment of Acidogenicity of Commercially Available Biscuits on Salivary pH - An in vivo Study

2020 ◽  
pp. 139-147
Author(s):  
B. Vivek Babu ◽  
Jayashri Prabakar
Keyword(s):  
Simple Random Sampling ◽  
In Vivo Study ◽  
Data Set ◽  
Group I ◽  
Significant Difference ◽  
Salivary Ph ◽  
The Difference ◽  
Group 2 ◽  
Inorganic Molecules

Saliva is a complex secretion consisting of 99% of water and remaining 1% of organic and inorganic molecules. Sucrose and starches are the predominant dietary carbohydrates in modern societies. Among all the foods consumed by children, chocolates and biscuits are the most common. Therefore this present in vivo study was conducted to assess the acidogenic effect of commercially available biscuits on salivary pH among 10 to 15 years old children. Study Design used in the study was In Vivo clinical study (Pilot Trail). The population collected in the survey was children between the age group of 10 - 15 years old children. 4 Groups were considered and 10 in each group. Group 1: Hide and Seek, Group 2: Good Day, Group 3: Dream and Cream, Group 4: Oreo. Sampling method used in the study was conducted as simple random sampling. Ethical approval of the study was obtained from Saveetha Institutional Review Board. Informed consent of the children were obtained from the parents. Descriptive statistics were expressed by means of mean and standard deviation. Shapiro Wilks test used to test the normality of the data set. Kruskal Wallis test was used to find the difference in mean Salivary pH between the groups and within the groups at Baseline, Immediate and after 15 min, 30 mins. A statistically significant difference in mean Salivary pH was observed between the groups at Immediate and after 30 mins (p<0.05). The mean Salivary pH was significantly dropped in Oreo, Dream cream and Hide & Seek groups at various time-periods. Based on the results of the present study, it can be concluded that maximum drop in mean salivary pH was observed in Group IV followed by Group II and Group I. It was observed that in all the groups, the pH gradually got back to near normal levels due to the buffering mechanism of saliva.

scholarly journals use of aspect in Czech L2

2003 ◽  
Vol 29 ◽  
pp. 177-194
Author(s):  
Barbara Schmiedtová
Keyword(s):  
English Learners ◽  
English Learner ◽  
Data Set ◽  
Lexical Meaning ◽  
Imperfective Aspect ◽  
Verbal Prefixes ◽  
Significant Difference ◽  
Verb Forms ◽  
The Difference ◽  
The Right

The focus of the present paper is on the difference between English and German learners‘ use of perfectivity and imperfectivity. The latter is expressed by means of suffixation (suffix -va-). In contrast, perfectivity is encoded either by suffixation (-nou-) or by prefixation (twenty different prefixes that mostly modify not only aspectual but also lexical properties of the verb). In the native Czech data set, there is no significant difference between the number of imperfectively and perfectively marked verb forms. In the English data, imperfectively and perfectively marked verb forms are equally represented as well. However, German learners use significantly more perfective forms than English learners and Czech natives. When encoding perfectivity in Czech, German learners prefer to use prefixes to suffixes. Overall, English learners in comparison to German learners encode more perfectives by means of suffixation than prefixation. These results suggest that German learners of Czech focus on prefixes expressing aspectual and lexical modification of the verb, while English learners rather pay attention to the aspectual opposition between perfective and imperfective. In a more abstract way, the German learner group focuses on the operations carried out on the left side from the verb stem while the English learner group concentrates on the operations performed on the right side qfrom the verb stem. This sensitivity can be to certain degree motivated by the linguistic devices of the corresponding source languages: English learners of Czech use imperfectives mainly because English has marked fully grammatical form for the expression of imperfective aspect – the progressive -ing form. German learners, on the other hand, pay in Czech more attention to the prefixes, which like in German modify the lexical meaning of the verb. In this manner, Czech prefixes used for perfectivization function similar to the German verbal prefixes (such as ab-, ver-) modifying Aktionsart.  

scholarly journals Methodology for Identifying the Boundaries of Agglomerations based on Statistical Data

2021 ◽  
Vol 17 (1) ◽  
pp. 44-58
Author(s):  
D.E. Tolmachev Tolmachev ◽  
Pavel D. Kuznetsov ◽  
Sergey V. Ermak
Keyword(s):  
Statistical Data ◽  
Population Distribution ◽  
Mutual Influence ◽  
Sverdlovsk Oblast ◽  
Russian Regions ◽  
Circular Migration ◽  
Settlement System ◽  
Data Set ◽  
Significant Difference ◽  
The Difference

Significant difference in development between the municipalities is an obstacle for achieving economic sustainability in many Russian regions. Regional development strategies and plans of various municipalities often cannot be synchronised because of their incompatibility. Moreover, municipalities usually lack necessary resources to implement their strategies. To solve these problems, we identified groups of municipalities (key units of the settlement system (KUSS)) based on the existing socio-eco- nomic relations, common challenges and development potential. We propose a methodology for identifying KUSS and describe its application. This methodology relies on statistical data available at the municipal level. To assess the interconnection of municipalities, we used 6 statistical socio-economic indicators and 1 integrated index of Gross Municipal Product (GMP). The difference in the first 6 indicators of the development of municipalities demonstrated, that less developed municipalities tend to more developed ones. We used the values of gross municipal product to define high mutual attraction of large municipalities (similar to the gravity model). The distance between municipalities reduced their mutual influence. Due to the limited data set, it was necessary to consider the reliability of the identified inter-municipal relations. Thus, we compared the obtained results with empirical data on population distribution and circular migration between municipalities in the region. The comparison of our calculations and actual data showed high precision of the presented methodology. The resulting grouping of municipalities allowed identifying 21 key units of the settlement system in Sverdlovsk oblast. The proposed methodology can be used for deter- mining large groups of municipalities in Sverdlovsk oblast, as well as in other Russian regions.

scholarly journals Diversity patterns of nonmammalian cynodonts (Synapsida, Therapsida) and the impact of taxonomic practice and research history on diversity estimates

Paleobiology ◽  
2018 ◽  
Vol 45 (1) ◽  
pp. 56-69 ◽  
Author(s):  
Marcus Lukic-Walther ◽  
Neil Brocklehurst ◽  
Christian F. Kammerer ◽  
Jörg Fröbisch
Keyword(s):  
Fossil Record ◽  
Phylogenetic Diversity ◽  
Terrestrial Ecosystems ◽  
Late Triassic ◽  
Geological Time ◽  
The Difference ◽  
Permian Mass Extinction ◽  
Taxic Diversity ◽  
The Impact ◽  
Diversity Estimates

AbstractNonmammalian cynodonts represent a speciose and ecologically diverse group with a fossil record stretching from the late Permian until the Cretaceous. Because of their role as major components of Triassic terrestrial ecosystems and as the direct ancestors of mammals, cynodonts are an important group for understanding Mesozoic tetrapod diversity. We examine patterns of nonmammalian cynodont species richness and the quality of their fossil record. A supertree of cynodonts is constructed from recently published trees and time calibrated using a Bayesian approach. While this approach pushes the root of Cynodontia back to the earliest Guadalupian, the origins of Cynognathia and Probainognathia are close to their first appearance in the fossil record. Taxic, subsampled, and phylogenetic diversity estimates support a major cynodont radiation following the end-Permian mass extinction, but conflicting signals are observed at the end of the Triassic. The taxic diversity estimate shows high diversity in the Rhaetian and a drop across the Triassic/Jurassic boundary, while the phylogenetic diversity indicates an earlier extinction between the Norian and Rhaetian. The difference is attributed to the prevalence of taxa based solely on teeth in the Rhaetian, which are not included in the phylogenetic diversity estimate. Examining the completeness of cynodont specimens through geological time does not support a decrease in preservation potential; although the median completeness score decreases in the Late Triassic, the range of values remains consistent. Instead, the poor completeness scores are attributed to a shift in sampling and taxonomic practices: an increased prevalence in microvertebrate sampling and the naming of fragmentary material.

Infaunal response during the end-Permian mass extinction

2020 ◽  
Vol 133 (1-2) ◽  
pp. 91-99 ◽  
Author(s):  
Mao Luo ◽  
Luis A. Buatois ◽  
G.R. Shi ◽  
Zhong-Qiang Chen
Keyword(s):  
Mixed Layer ◽  
Mass Extinction ◽  
Fossil Record ◽  
Sea Water ◽  
The Body ◽  
Trace Fossil ◽  
Late Permian ◽  
Data Set ◽  
Permian Mass Extinction ◽  
Body Fossil

Abstract The end-Permian mass extinction (EPME) profoundly shaped shallow marine ecosystems. Although much has been learned about this event based on the body-fossil record, the global infaunal response to the EPME, as represented by ichnofossils, is much less understood. Here we analyze secular changes in ichnodiversity and ichnodisparity from the late Permian to the Middle Triassic based on a global trace-fossil data set. Results show that, in contrast to the body-fossil record, late Permian global ichnodiversity and ichnodisparity maintained their level until the Griesbachian, followed by a sharp loss in the Dienerian. Notably, the Griesbachian shows an unusual dominance of shallower tiers. The discrepancy between the body- and trace-fossil record is interpreted to be the result of the resurgence of widespread microbial matgrounds in the Griesbachian that aided the preservation of surface, semi-infaunal, and shallow-tier ichnofossils. Our study shows that the EPME strongly affected the sediment mixed layer, allowing the preservation of shallower tier trace fossils. The disappearance of the mixed layer in the earliest Triassic may have enhanced pyrite burial in sediments and inhibited its further re-oxidation, therefore impacting sea water sulfate concentrations.

scholarly journals Confidence intervals for pulsed mass extinction events

Paleobiology ◽  
2007 ◽  
Vol 33 (2) ◽  
pp. 324-336 ◽  
Author(s):  
Steve C. Wang ◽  
Philip J. Everson
Keyword(s):  
Confidence Intervals ◽  
Mass Extinction ◽  
Fossil Record ◽  
Marine Invertebrates ◽  
Ratio Test ◽  
Mass Extinctions ◽  
Data Set ◽  
Triassic Boundary ◽  
Multiple Pulses ◽  
Extinction Events

Many authors have proposed scenarios for mass extinctions that consist of multiple pulses or stages, but little work has been done on accounting for the Signor-Lipps effect in such extinction scenarios. Here we introduce a method for computing confidence intervals for the time or stratigraphic distance separating two extinction pulses in a pulsed extinction event, taking into account the incompleteness of the fossil record. We base our method on a flexible likelihood ratio test framework that is able to test whether the fossil record is consistent with any extinction scenario, whether simultaneous, pulsed, or otherwise. As an illustration, we apply our method to a data set on marine invertebrates from the Permo-Triassic boundary of Meishan, China. Using this data set, we show that the fossil record of ostracodes and that of brachiopods are each consistent with simultaneous extinction, and that these two extinction pulses are separated by 720,000 to 1.2 million years with 95% confidence. With appropriate data, our method could also be applied in other situations, such as tests of origination patterns, coordinated stasis, and recovery after a mass extinction.

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