Observations below multiple lower limits of quantification: How to estimate the mean and variance

Multiple lower limits of quantification (MLOQs) result if various laboratories are involved in the analysis of concentration data and some observations are too low to be quantified. For normally distributed data under MLOQs there exists only the multiple regression method of Helsel to estimate the mean and variance. We propose a simple imputation method and two new maximum likelihood estimation methods: the multiple truncated sample method and the multiple censored sample method. A simulation study is conducted to compare the performances of the newly introduced methods to Helsel's via the criteria root mean squared error (RMSE) and bias of the parameter estimates. Two and four lower limits of quantification (LLOQs), various amounts of unquantifiable observations and two sample sizes are studied. Furthermore, the robustness is investigated under model misspecification. The methods perform with decreasing accuracy for increasing rates of unquantified observations. Increasing sample sizes lead to smaller bias. There is almost no change in the performance between two and four LLOQs. The magnitude of the variance impairs the performance of all methods. For a smaller variance, the multiple censored sample method leads to superior estimates regarding the RMSE and bias, whereas Helsel's method is superior regarding the bias for a larger variance. Under model misspecification, Helsel's method was inferior to the other methods. Estimating the mean, the multiple censored sample method performed better, whereas the multiple truncated sample method performs best in estimating the variance. Summarizing, for a large sample size and normally distributed data we recommend to use Helsel's method. Otherwise, the multiple censored sample method should be used to obtain estimates of the mean and variance of data including MLOQs.     

End-Permian stratigraphic timeline applied to the timing of marine and non-marine extinctions

A latest Permian timeline (251.9 Ma) can be constructed from the perspectives of: a global nickel spike attributed to emissions from the coeval Siberian flood-basalt eruptions, the correlative end-Permian marine mass extinction (EPME), a transition from reversed to normal paleomagnetism, and a negative anomaly in δ¹³C_carb and δ¹³C_org. In a number of marine and non-marine localities, this timeline is also correlated (to within ≤30 ky) with palynological evidence for the latest Permian destruction of terrestrial vegetation and the accompanying short-lived global fungal (Reduviasporonites) event. This correlation suggests that devastation in marine and non-marine environments was essentially coeval at a time marked by hyperthermal conditions and anoxic oceans.We utilized this proposed timeline to estimate the relative timing of the extinction of latest Permian vertebrates in the Karoo Basin of South Africa. In several sections in the Karoo, the LAD of the therapsid Dicynodon, is correlated with the proposed timeline. In the Carlton Heights section in the Karoo we estimate that the palynological changes and the fungal event occurred within ≤30 ky of the LAD of Dicynodon. Further sampling in the Karoo and other Permian–Triassic non-marine basins would help to clarify the relative timing of the global marine extinctions, plant devastation and the disappearance of non-marine vertebrates.     

Granulomatous and lymphocytic interstitial lung disease diagnosed by transbronchial lung cryobiopsy

Granulomatous and lymphocytic interstitial lung disease is a pulmonary complication of common variable immune deficiency with significant morbidity and increased mortality. Diagnosis has historically been obtained by surgical lung biopsy as transbronchial biopsy typically yields insufficient tissue for definitive diagnosis from a disease process with a patchy distribution. However, the potential for significant morbidity and mortality with surgical lung biopsy exists, necessitating the development of alternative diagnostic approaches. We present a case of granulomatous and lymphocytic interstitial lung disease confirmed through minimally invasive transbronchial lung cryobiopsy and discuss the role of this modality in diagnosing interstitial lung disease.     

New associations of Carnian gastropods from Mežica region in the Karavanke Mountains of Slovenia

Two gastropod assemblages from the Carnian (Upper Triassic) Raibl Beds of the Mežica region (Karavanke Mountains, Slovenia) are described. The almost monospecific, older assemblage from Mežica Mine was found as a thin shell pavement in the clastic sequence. This association apparently originated during a period of reduced sedimentation. The younger assemblage from Helena Creek was found at the upper surface of an oolitic and oncoidal limestone and represents a more diversified fauna of a crinoid/coelenterate/polychaete meadow. Together, both assemblages contain 11 gastropod species. Five of them are left in open nomenclature, two are known from other localities in the Alps, and the remaining four are new. The new species are Sloeudaronia karavankensis (Skeneidae), Helenostylina mezicaensis (Coelostylinidae), Ampezzopleura slovenica and Striazyga crnaensis (Zygopleuridae). Two new genera, Sloeudaronia (Skeneidae) and Helenostylina (Coelostylinidae), are described.An erratum to this article can be found at     

Late Paleozoic–early Mesozoic continental biostratigraphy — Links to the Standard Global Chronostratigraphic Scale

Nonmarine biostratigraphic/biochronologic schemes have been created for all or parts of the late Carboniferous–Middle Triassic using palynomorphs, megafossil plants, conchostracans, blattoid insects, tetrapod footprints and tetrapod body fossils, and these provide varied temporal resolution. Cross correlation of the nonmarine biochronologies to the Standard Global Chronostratigraphic Scale has been achieved in some parts of the late Carboniferous–Middle Triassic in locations where nonmarine and marine strata are intercalated, the nonmarine strata produce biochronologically significant fossils and the marine strata yield fusulinids, conodonts and/or ammonoids. Other cross correlations have been aided by magnetostratigraphy, chemostratigraphy and a growing database of radioisotopic ages. A synthetic nonmarine biochronology for the late Carboniferous–Middle Triassic based on all available nonmarine index fossils, integrated with the Standard Global Chronostratigraphic Scale, is presented here. The focus is on the nonmarine biostratigraphy/biochronology of blattoid insects, conchostracans, branchiosaurid amphibians, tetrapod footprints and tetrapod body fossils within the biochronological framework of land-vertebrate faunachrons. Correlation to the Standard Global Chronostratigraphic Scale presented here is divided into seven time intervals: Pennsylvanian, Carboniferous–Permian boundary, Cisuralian, Guadalupian, Lopingian, Permian–Triassic boundary and Early to Middle Triassic. The insects, conchostracans and branchiosaurs provide robust nonmarine correlations in the Pennsylvanian–Cisuralian, and the footprints and tetrapod body fossils provide robust correlations of varied precision within the entire Pennsylvanian–Middle Triassic. Radioisotopic ages are currently the strongest basis for cross correlation of the nonmarine biostratigraphy/biochronology to the Standard Global Chronostratigraphic Scale, particularly for the Pennsylvanian–Cisuralian. Chemostratigraphy and magnetostratigraphy thus far provide only limited links of nomarine and marine chronologies. Improvements in the nonmarine-marine correlations of late Paleozoic–Triassic Pangea require better alpha taxonomy and stratigraphic precision for the nonmarine fossil record integrated with more reliable radioisotopic ages and more extensive chemostratigraphic and magnetostratigraphic datasets.     

Parafurnishius,an Induan (Lower Triassic) conodont new genus from northeastern Sichuan Province,southwest China and its evolutionary implications

A fundamental aspect of taxonomy at the generic level, critical to understand Early Triassic conodont evolution, is the composition of the multielement apparatus. In this paper, we document a platform-bearing new conodont genus, Parafurnishius n. gen., as well as its multielement apparatus from the Griesbachian Feixianguan Formation (Lower Triassic) in Xuanhan County, northeastern Sichuan Province, southwest China. The new conodont genus is characterized by numerous robust and irregularly distributed conical denticles with variable platform morphology that has a possible affinity with the P₁ elements of Furnishius. These genera have apparatuses similar to those of Ellisonia and are classified with the family Ellisoniidae. The strong intraspecific variation of P₁ elements and the growth series within the entire sample population suggest that Parafurnishius may have evolved from the Griesbachian Isarcicella by developing random denticle positioning away from the platform centre, and then possibly evolved into younger Triassic Furnishius by developing a stable blade configuration. This preferred interpretation implies an ellisonid apparatus for Isarcicella. Alternatively, Parafurnishius may have evolved from Ellisonia and developed a homeomorphic P₁ element with Isarcicella. This new taxon has strong intraspecific variation of denticle growth orientation during the Early Triassic.     

Contrast adaptation to time constraints on development of two pre-dispersal predators of dandelion (<Emphasis Type="Italic">Taraxacum officinale</Emphasis>) seed

Pre-dispersal seed predators of quickly maturing inflorescences of Asteraceae are constrained by shortage of development time. At seed dispersal, they should pupate or, if still immature, relocate into another inflorescence. To investigate how dominant coleopteran predators of dandelion seed, Glocianus punctiger (Curculionidae) and Olibrus bicolor (Phalacridae), cope with time limitation we combined observation (development and temperature of dandelion capitulum, thermal constants of predator development, age structure of larval populations at seed dispersal) and analogy (“rate isomorphy” in predator development, comparing “model” coleopteran species with similar temperature requirements). Development of a dandelion capitulum takes 21 days. The time available to G. punctiger (140–190 day degrees, development threshold 6.3°C) is sufficient to complete development and pupate after seed dispersal. By contrast, only 30–50 day degrees are available to O. bicolor (threshold 13.5°C) and this is not enough to complete development and consequently immature larvae should move to other capitula to continue feeding until pupation. These contrast strategies which are determined by this thermal adaptation, are accompanied by differences in larval morphology. The “cold adapted” G. punctiger has an apodous larva not capable of migrating between capitula while the “warm adapted” O. bicolor has a mobile campodeiform larva capable of migration.     

Nonmarine ostracodes at the Permian–Triassic boundary of the central part of the East European Platform

Extensive geological and paleontological materials from the upper Permian and the Lower Triassic of the East European Platform had been accumulated by the end of the 20th century. Recently obtained new data indicate the stratigraphic continuity of the East European Permian–Triassic succession. The Permian–Triassic boundary is in many sections associated with the boundary between the Zhukovian and Vokhmian regional stages. New stratigraphic data have led to the revision of the temporal distribution of Zhukovian and Vokhmian ostracodes. In contrast to previous ideas, the rapid development of genus Gerdalia already began in the Zhukovian time rather than in the Vokhmian. At the same time, the first Darwinula of the Triassic type also appeared in the Zhukovian. A proportion of the Permian species were found to cross the boundary between Zhukovian and Vokhmian. The degree of similarity between the Permian and Triassic ostracode assemblages turns out to be much higher than previously recognized.     

Stratigraphy and sedimentology of Muschelkalk carbonates of the Southern Iberian Continental Palaeomargin (Siles and Cehegín Formations,Southern Spain)

The Triassic sediments of the External Zones of the Betic Cordillera were deposited on the Southern Iberian Continental Palaeomargin. Two coeval Ladinian formations, namely the Siles Formation and the Cehegín Formation, are described to illustrate the facies and lithostratigraphic variability in the Muschelkalk carbonates. There has been some dispute over the number of carbonate units present in the Siles Formation. Our studies assign a tectonic origin to these recurrent carbonate units. Both formations comprise only one carbonate unit, which is correlated to the Upper Muschelkalk of the Catalan and Germanic basins and some Iberian Range sections. To characterize the sedimentological features of these formations, 14 facies were defined. The most widespread sediment was originally lime mud, although bioclastic deposits are also common. In the facies succession, a main transgressive-regressive sequence could be identified. According to the facies model proposed here, a muddy coastal and shallow-water platform prograded over mid ramp deposits. There is no evidence for a seawards reefal or oolitic-bioclastic sandy barrier. The most significant feature of this sedimentary interpretation is that these carbonate facies show clear characteristics of an epicontinental platform.